ansi aihaz9.5 2012(laboratoryventilation)

8/19/2019 ANSI AIHAZ9.5 2012(LaboratoryVentilation)

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BY THE ANSI/AIHA Z9.5 SUBCOMMITTEE

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ANSI/AIHA Z9.5–2012

LaboratoryVentilation


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ANSI/AIHA ® Z9.5–2012

ANSI/AIHA ® Z9.5 – 2012

Laboratory Ventilation

Secretariat

American Industrial Hygiene Association

Approved April 26, 2012

Copyright AIHA® For personal use only. Do not distribute.


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Published by

American Industrial Hygiene Association3141 Fairview Park Drive, Suite 777, Falls Church, VA 22042www.aiha.org

Copyright © 2012 by the American Industrial Hygiene Association

All rights reserved.

No part of this publication may be reproduced in anyform, in an electronic retrieval system or otherwise,without the prior written permission of the publisher.

Printed in the United States of America.

ISBN 978-1-935082-34-7

Stock Number: LVEA12-437

American

National

Standard

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whose name appears on the title page of this standard.

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ContentsPage

Foreword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . iii1 Scope, Application and Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

1.1. Scope and Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11.2. Purpose . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

2 Laboratory Ventilation Management Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.1. General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 32.2. Chemical Hygiene Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.3. Responsible Person . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 72.4. The Role of Hazard Assessment in Laboratory Ventilation Management . . . 82.5. Recordkeeping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

3 Laboratory Fume Hoods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 123.1. Design and Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 133.2. Laboratory Fume Hood Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 163.3. Hood Airflow and Monitoring (Design and Performance Specifications) . . . 22

4 Other Containment Devices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.1. Gloveboxes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 284.2. Ductless Hoods. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 34

4.3. Special Purpose Hoods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 375 Laboratory Ventilation Systems Design. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 38

5.1. Laboratory Design . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 385.2. Laboratory Airflow Management. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 405.3. Supply Air . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 465.4. Exhaust. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

6 Commissioning and Routine Performance Testing . . . . . . . . . . . . . . . . . . . . . . . 656.1. Performance specifications, tests, and instrumentation . . . . . . . . . . . . . . . . 656.2. Commissioning of Laboratory Ventilation Systems. . . . . . . . . . . . . . . . . . . . 736.3. Commissioning Fume Hoods and Different Types of Systems. . . . . . . . . . . 756.4. Ongoing or Routine Hood and System Tests . . . . . . . . . . . . . . . . . . . . . . . . 81

7 Work Practices. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 827.1. General Requirements and Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 827.2. Posting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837.3. Operating Conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 837.4. Training . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 83

8 Preventive Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 848.1. Operations During Maintenance Shutdown . . . . . . . . . . . . . . . . . . . . . . . . . 848.2. Housekeeping Before and After Maintenance . . . . . . . . . . . . . . . . . . . . . . . 848.3. Safety for Maintenance Personnel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 858.4. Work Permits and Other Communications . . . . . . . . . . . . . . . . . . . . . . . . . . 858.5. Records. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 868.6. Testing and Monitoring Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 868.7. Monitoring Fans, Motors, and Drives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 888.8. Critical Service Spares . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 88

8.9. Critical Service Instrumentation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 898.10. Performance Monitoring Equipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 89

9 Air Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899.1. Supply Air Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899.2. Exhaust Air Cleaning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 899.3. Filtration for Recirculation. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 909.4. Testing and Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 92



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Appendices

Appendix 1 Definitions, Terms, and Units . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 93

Appendix 2 Referenced Standards and Publications . . . . . . . . . . . . . . . . . . . . . . . . . . 98Appendix 3 Selecting Laboratory Stack Designs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 101Appendix 4 Audit Form for ANSI/AIHA Z9.5-2010 . . . . . . . . . . . . . . . . . . . . . . . . . . . 108Appendix 5 Sample Table of Contents for Laboratory Ventilation

Management Plan . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 129



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Foreword (This foreword is not part of the American National Standard Z9.5–2012.)

General coverage. This standard describes required and recommended practices for the design and oper-ation of laboratory ventilation systems used for control of exposure to airborne contaminants. It is intend-ed for use by employers, architects, industrial hygienists, safety engineers, Chemical Hygiene Officers,Environmental Health and Safety Professionals, ventilation system designers, facilities engineers, mainte-

nance personnel, and testing and balance personnel. It is compatible with the ACGIH ® Industrial Ventilation: A Manual of Recommended Practices , ASHRAE ventilation standards, and other recognizedstandards of good practice.

HOW TO READ THIS STANDARD. The standard is presented in a two-column format. The left col-

umn represents the requirements of the standard as expressed by the use of “shall.” The right col-umn provides description and explanation of the requirements and suggested good practices or

examples as expressed by the use of “should.” Appendices 1 and 2 provide supplementary infor-mation on definitions and references. Appendix 3 provides more detailed information on stack

design. Appendix 4 provides a sample audit document and Appendix 5 presents a sample table ofcontents for a Laboratory Ventilation Management Plan.

Flexibility. Requirements should be considered minimum criteria and can be adapted to the needs of the

User establishment. It is the intent of the standard to allow and encourage innovation provided the mainobjective of the standard, “control of exposure to airborne contaminants,” is met. Demonstrably equal orbetter approaches are acceptable. When standard provisions are in conflict, the more stringent applies.

Response and Update. Please contact the standards coordinator at AIHA ® , 3141 Fairview Park Drive,Suite 777, Falls Church, VA 22042, if you have questions, comments, or suggestions. As with all ANSIstandards, this is a “work in progress.” Future versions of the standard will incorporate suggestions andrecommendations submitted by its Users and others.

This standard was processed and approved for submittal to ANSI by the Z9 Accredited StandardsCommittee on Health and Safety Standards for Ventilation Systems. Committee approval of the standarddoes not necessarily imply that all committee members voted for its approval. At the time it approved thisstandard the Z9 Committee had the following members:

Thomas Smith, ChairTheodore Knutson, Vice ChairDavid Hicks, Secretariat RepresentativeAt the time of publication, the Secretariat Representative was David Hicks.

Organization Represented . . . . . . . . . . . . . . . . . . . . . . . .Name of Representative ACGIH® . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .G. KnutsonASHRAE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .T. SmithAmerican Foundry Society . . . . . . . . . . . . . . . . . . . . . . . .R. ScholzASSE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .P. OsleyGlobal Finishing Solutions . . . . . . . . . . . . . . . . . . . . . . . .G. Raifsnider

National Association of Metal Finishers . . . . . . . . . . . . . .K. HankinsonNIH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .F. MemarzadehNIOSH . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .M. ElliottOSHA . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .L. Hathon

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Individual Members D.J. BurtonS. CrooksL. DiBerardinisC. FigueroaS. GunselE. Pomer

N. McManusD. O’BrienJ. PriceK. PaulsonM. RollinsJ. Sheehy

Subcommittee Z9.5 on Laboratory Ventilation, which developed this standard, had the following members:

Steve Crooks, ChairJames Coogan, Vice Chair

L. DiBerardinis

D. Walters (*)D.J. BurtonD. HitchingsT.C. SmithV. NeumanJ.M. PriceG. KnutsonG. SharpS. HauvilleR.A. (Bob) HenryM. TschidaC.J. McAfeeR.A. DeLucaP. PinkstonK. KretchmanS. LengerichP. Carpenter (Technical Resource)A. Kolesnikov (Observer)

* retired during the standard’s development

iv

* Contributing member of Z9.5 subcommittee but not a voting member of the full Z9 Committee at the time of standard approval.



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ANSI/AIHA Z9.5–2012AMERICAN NATIONAL STANDARD

American National Standard

for Laboratory VentilationRequirements of the Standard

1 Scope, Application and Purpose

1.1 Scope and Application

This standard applies to the ventilation in most lab-oratories and is written for all laboratory ventilationstakeholders. An emphasis is placed on those withlegal responsibilities and liability for providing a

safe laboratory. However, users/operators, industri-al hygienists, other safety and environmental pro-fessionals will also find the standard written fortheir needs.

The standard cannot establish strict liability in allcases but does attempt to fix accountability in manyrelationships that exist with its context. Please notethat such relationships are defined throughout thestandard and generally encompass the following:administration - occupant; employer - employee;management - staff; owner - occupant; owner - tenant;teacher - student; designer - owner, etc.

This standard does not apply to the following typesof laboratories or hoods except as it may relate togeneral laboratory ventilation:

• animal facilities,• biosafety cabinets,• explosives laboratories,• high containment facilities (e.g., BSL 3, BSL 4,

facilities operating under “chemical suretyplans,” etc.),

• laminar flow hoods and isolators (e.g., a clean

bench for product protection, not employeeprotection), and

• radioisotope laboratories.

General laboratory safety practices are not includ-ed except where they may relate to the ventilationsystem’s proper function or effectiveness.

Clarification and Explanation of the Requirements

Laboratories conduct teaching, research, qualitycontrol, and related activities and should satisfyseveral general objectives, in addition to being suit-ed for the intended use they should

• be energy efficient without sacrificing safety,compliance, or space condition requirements,

• be safe places to work,• comply with environmental, health, and safety

regulations, and• meet any necessary criteria for the occupants

and technology involved in terms of control oftemperature, humidity, and air quality.

Appendix 2 offers several references providinginformation, guidelines or specific requirements for

• laboratory animals – AAALAC,• biosafety cabinets – NSF,• biohazardous materials – ABSA, and CDC,• flammables, pyrophoric and explosives –

NFPA, ISEE, and IMC,• high containment facilities – CDC, ISPE, and

USAMRICD,• laminar flow hoods and isolators – NSF and

CETA,• radioactive materials – NRC, and• special environmental requirements for prod-

uct protection such as contamination controlfrom particulates – CETA and IEST.

This standard does not apply to comfort consider-ations unless they have an effect on contaminantcontrol ventilation.

1



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1.2 Purpose

The primary purpose of this standard is to

establish minimum requirements and bestpractices for laboratory ventilation systems toprotect personnel from physical harm andoverexposure to harmful or potentially harm-ful airborne contaminants generated withinthe laboratory. The standard’s requirementsalso aim to protect property where relevant.

In light of significant efforts and initiative toreduce greenhouse gases, the standard alsoconfronts energy considerations, especiallywhere there is a potential to impact workerhealth and safety.

This standard:

• informs the designer of the requirementsand conflicts among various criteria rela-tive to laboratory ventilation,

• informs the user of information neededby designers, and

• sets forth ventilation requirements thatwill, combined with appropriate workpractices, achieve acceptable concentra-tions of air contaminants.

Thus, this standard provides insight on howinadequate ventilation or other ventilationsystem deficiencies can impact safety andcontainment. However, this standard cannotprovide designers and users with everythingneeded for conducting hazard assessments.Designers and users are thereby cautionedto not misconstrue the purpose of this stan-dard as addressing comprehensive hazardcontrol for particular hazards posed by alloperations that may occur in a laboratoryroom. See Section 2.4.

Persons responsible for laboratory operations and thoseworking within laboratories may not be aware of howventilation can impact environment, health and safety.On the other hand, ventilation system design profession-als cannot be expected to be fully aware of all the par-ticular hazards posed by every type of operation thatmay occur in a laboratory.



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2 Laboratory VentilationManagement Plan

2.1 General Requirements

Management shall establish a LaboratoryVentilation Management Plan (LVMP) toensure proper selection, operation, use, andmaintenance of laboratory ventilation equip-ment.

An LVMP shall be implemented to ensureproper operation of the lab ventilation sys-tems, help protect laboratory personnel work-ing with potentially hazardous airborne mate-rials, provide satisfactory environmental airquality and maintain efficient operation of the

laboratory ventilation systems.

The LVMP shall provide guidelines and spec-ifications for

• commissioning to verify proper perfor-mance prior to occupancy and use ofthe laboratory hoods,

• description of training programs forensuring proper use, testing and main-tenance of the laboratory hoods,

• design of laboratory ventilation systems,• maintenance procedures for providing

and documenting reliable operation,• periodic confirmation that the ventilation

system is used properly,• selection of appropriate laboratory

hoods,• specification of monitors to continuously

verify proper operation of the laboratoryhoods, and

• standard procedures for routine testing.

Laboratory workers and other building occupantsdepend on proper operation of the ventilation systemsto provide safe, comfortable and productive environ-ments for work with hazardous materials. The ventila-tion systems comprise numerous sub-systems andindividual components including air handling units,exhaust fans, airflow controls, chemical fume hoods,biological safety cabinets and other local exhaustdevices. Ensuring safe and efficient operation of labo-ratory ventilation systems requires careful manage-ment of the systems from design to operation.

An LVMP provides the framework for keeping the sys-tems operating to satisfy the primary functionalrequirements of building personnel.

Management participation in the selection, design,and operation of laboratory ventilation systems is crit-ical to the overall success of the effort. The programshould be supported by top management. A sampleTable of Contents for a Laboratory VentilationManagement Plan is included in Appendix 5.

Management should understand that ventilation equip-ment is not furniture, but rather it is part of installedcapital equipment. It must be interfaced to the buildingventilation system.

An effective LVMP should satisfy several generalobjectives. It should;

• define the responsibilities of departments andpersonnel responsible for ensuring proper opera-tion of the systems,

• describe how the systems are to be commis-sioned, tested and maintained,

• provide a description of the systems and define

the functional requirements,• provide specifications for design and operation of

the laboratory hood systems, and• result in safe, dependable and efficient operation

of the laboratory ventilation systems.



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2.1.1 Exposure Control Devices

Adequate laboratory fume hoods, specialpurpose hoods, or other engineering controls

shall be used when there is a possibility ofemployee overexposure to air contaminantsgenerated by a laboratory activity.

OSHA requires that, employers are responsi-

ble for ensuring that exposure controldevices are functioning properly and imple-menting feasible control measures to reduceemployee exposures if the exposures exceedthe PELs (§29 CFR 1910.1450(e)(3)(iii)).Furthermore, if an employer discoversthrough their hazard assessment efforts oremployee feedback, that exposure controldevices are not effectively reducing employ-ee exposures, it is the employer's responsi-bility to adjust controls or replace engineer-ing controls as necessary.

The capture and/or containment of theselected exposure control device shall beconsidered adequate if, in combination withprudent practice, laboratory worker exposurelevels are maintained below published or in-house exposure limits or below those limitsidentified in applying or using publishedexposure limits.

OSHA specifically states the following

requirements in regards to employee expo-sure monitoring:

1910.1450(d) Employee exposure determi-nation

1910.1450(d)(1) Initial monitoring.

There are numerous exposure control devices including:

• biological safety cabinets,• gloveboxes,

• aboratory fume hoods,

• local exhaust hoods, and

• other ventilated enclosures

Exposure control devices are available in a wide varietyof designs with different capabilities and limitations.Selecting the appropriate exposure control device isimportant to ensuring adequate protection for the labora-tory worker.

OSHA does not promulgate specific control device test-

ing protocols

The performance of an exposure control device is ulti-mately determined by its ability to control exposure towithin applicable standards or other safe limits.

If exposure limits [e.g., Occupational Safety and HealthAdministration Permissible Exposure Limits (OSHAPELs), National Institute for Occupational Safety andHealth Recommended Exposure Limits (OSHA RELs),American Conference of Governmental IndustrialHygienists threshold limit values (ACGIH ® TLVs ® ),American Industrial Hygiene Association WorkplaceEnvironmental Exposure Limits (AIHA ® WEELs ® ),German MAKs, (maximum admissible concentrations)]or similar limits used in prescribing and/or assessing safe

handling do not exist for chemicals used in the laborato-ry, the employers should establish comparable in-houseguidelines. Qualified industrial hygienists and toxicolo-gists working in conjunction may be best suited toaccomplish this need.



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The employer shall measure the employee'sexposure to any substance regulated by astandard which requires monitoring if thereis reason to believe that exposure levels for

that substance routinely exceed the actionlevel (or in the absence of an action level, thePEL).

1910.1450(d)(2) Periodic monitoring.

If the initial monitoring prescribed by para-graph (d)(1) of this section disclosesemployee exposure over the action level (orin the absence of an action level, the PEL),the employer shall immediately comply withthe exposure monitoring provisions of therelevant standard.

1910.1450(d)(3) Termination of monitoring.

Monitoring may be terminated in accordancewith the relevant standard.

1910.1450(d)(4) Employee notification ofmonitoring results. The employer shall, with-in 15 working days after the receipt of anymonitoring results, notify the employee ofthese results in writing either individually orby posting results in an appropriate locationthat is accessible to employees.

Section 8.C.5 Testing and Verification of PrudentPractices in the Laboratory:

Handling and Disposal of Chemicals, 1995 states the fol-

lowing with regards to exposure monitoring for fume hoodusers. “Perhaps the most meaningful method for evaluat-ing hood performance is to measure worker exposurewhile the exposure control device is being used for itsintended purpose. Where exposure limits and analyticalmethods exist, personal air-sampling devices can beworn by the user and worker exposure (both excursionpeak and time-weighted average) can be measuredusing standard industrial hygiene techniques. The criteri-on for evaluating the device should be the desired perfor-mance (i.e., does the device contain chemical at thedesired worker-exposure level?). A sufficient number ofmeasurements should be made to define a statistically

significant maximum exposure based on worst-caseoperating conditions. Direct-reading instruments areavailable for determining the short-term concentrationexcursions that may occur in laboratory hood use.”

Measuring for an “overexposure” to chemicals implies ameans of defining an unsafe limit and having an analyti-cal means of determining when such limit is exceeded.Since neither are commonplace or practical, surrogateshave been useful in empirical determinations. However, ifan employee believes that he or she is overexposed tohazardous chemicals despite their use of an exposurecontrol device, he or she should have an internal mecha-nism for resolving their concern (e.g., informing a super-visor). OSHA requires that any such employee is provid-ed an opportunity to receive an appropriate medicalexamination. Other similar occurrences make it incum-bent on the employer to protect the employee and ensureadequate control measures (§29 CFR 1910.1450(g)(1)(i-iii). In the event an employer remains unresponsive to anemployee’s complaint, the employee would be encour-aged to seek other advice or external intervention (e.g.,filing a complaint with OSHA.)

In the European Union (EU,) Registration, Evaluation,

Authorization and Restriction of Chemicals (REACH) is ineffect and should be consulted as appropriate for hazardevaluation information impacting laboratories operatingwithin the scope of this standard.



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Chemical “hazard determination” shall be conduct-ed by chemical manufacturers and importers asrequired by the Occupational Safety and HealthAdministration's (OSHA) Hazard Communicationstandard, specifically, 29 CFR 1910.1200(d). Thisrequires that manufacturers and importers of chem-icals to identify chemical hazards so that employeesand downstream users can be informed about thesehazards.

2.1.2 Laboratory (Room) Ventilation Rate

The specific room ventilation rate shall be estab-lished or agreed upon by the owner or his or herdesignee.

2.1.3 Dilution Ventilation

Dilution ventilation shall be provided to control thebuildup of fugitive emissions and odors in the labo-ratory. The dilution rate shall be expressed in termsof exhaust flow in negatively pressurized laborato-ries and supply flow in positively pressurized labo-ratories.

Ventilation is a tool for controlling exposure.Contaminants should be controlled at the source.Potential sources should be identified and expo-sure control devices should be specified asappropriate to control emissions at the source.(See Sections 3 and 4) All sources and assump-tions should be clearly defined and documented.

An air exchange rate (air changes per hour) can-not be specified that will meet all conditions.Furthermore, air changes per hour is not theappropriate concept for designing contaminantcontrol systems.

Excessive airflow with no demonstrable safetybenefit other than meeting an arbitrary air changerate can waste considerable energy.

Control of hazardous chemicals by dilution alone,in the absence of adequate laboratory fumehoods, is seldom effective in protecting laboratoryusers. It is almost always preferable to capturecontaminants at the source, than attempt to dis-place or dilute them by room ventilation.



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2.2 Chemical Hygiene Plan

The laboratory shall develop a ChemicalHygiene Plan according to the OSHA

Laboratory Standard (29 CFR 1910.1450).

The plan shall address the laboratory opera-tions and procedures that might generate aircontamination in excess of the requirementsof Section 2.1.2. These operations shall beperformed inside exposure control devicesadequate to attain compliance.

The plan shall address emergencies and acci-dents, as well as ordinary operation.

2.3 Responsible Person

In each operation using laboratory ventilation

systems, the user shall designate a “responsi-ble person.”

Nevertheless, dilution or displacement may removecontaminants not captured by a specifically applieddevice.

The quantity of dilution (or displacement) ventilationrequired is a subject of controversy. Typical dilution ven-tilation rates can range from 4 to 10 air changes perhour depending on heating, cooling, and comfort needsand the number and size of exposure control devices.

Although some laboratories do not fall under the OSHAStandard, a Chemical Hygiene Plan or Laboratory

Safety Standards (or manual) can establish properwork practices.

Persons participating in writing the plan should beknowledgeable in industrial hygiene, laboratory proce-dures and chemicals, the design of the ventilation sys-tems, and the system’s maintenance needs. The planshould be disseminated and become the basis foremployee training.

In the event of large accidental releases in the labora-tory room, away from exhausts and control systems,the laboratory owner should specify appropriate evacu-ation protocols. The plan may also include emergencyventilation modes. (See Section 5.2.3.)

The responsible person may have the following duties:

• Ensuring that existing conditions and equipmentcomply with applicable standards and codes,

• Ensuring that testing and monitoring are done onschedule,



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2.4 The Role of Hazard Assessment inLaboratory Ventilation Management

2.4.1 General Requirements

Employers shall ensure the existence of anongoing system for assessing the potential forhazardous chemical exposure.

Employers shall promote awareness that labo-ratory hoods are not appropriate controldevices for all potential chemical releases inlaboratory work.

The practical limits of knowing how each expo-sure control device is being or may be usedshall be considered when specifying designfeatures, performance criteria (commissioningand routine monitoring), or when seeking ener-gy savings. The responsible person as definedin Section 2.3 shall be consulted in making this

judgment.

Exposure control devices shall be functioning

properly and specific measures shall be takento ensure proper and adequate performance(refer to Section 2.1.1).

• Maintaining adequate records,• Participating in the design (new construction or

renovation) of the lab at the conception/ planning

stage (preferably as an IH or EHS professionalwith laboratory ventilation experience),

• Performing visual checks,• Training employees, and• Performing any other related task assigned by the

employer.

At a minimum, the responsible person should coordi-nate the above activities.

Much of this standard addresses a generic approachto exposure control. This is necessary because manyof the chemical hazards in a laboratory are chronic innature and an employee's ability to sense overexpo-sure is subjective.

The employer may determine that providing standardlaboratory hoods tested to the ANSI/ASHRAE 110standard and an “as installed” AI 0.1 rating are bestfor the types of chemical hazards and work beingperformed at the specific workplace. The assumptionthat follows is that users are trained to understandlimitations of the hood's control ability and would notuse it for work that, for example, should be performedin a glovebox. Alternatively, ensuring all hoods arecapable of meeting an AI 0.1 rating may not be nec-

essary, for example, if the only chemical being han-dled has an 8-hr time-weighted average (TWA) –

TLV ® exposure limit of 250 ppm.



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The employer shall establish criteria for deter-mining and implementing control measures toreduce employee exposure to hazardous

chemicals. Particular attention shall be givento the selection of control measures for chem-icals that are known to be extremely haz-ardous.

The following briefly describes an approach usedwithin laboratory ventilation management programs inassigning control measures given the ability (or inabil-ity) to assess specific day-to-day chemical exposure

situations.

Hazard assessments in general are geared towardidentifying chemicals, their release potential (source),their transmission route (path), and their possibleroutes of entry into the body (receiver). It is criticalthat assessments be conducted in a competent man-ner such that the source-path-receiver “picture” is notmisconstrued.

Hazard assessments may incorporate results fromtracer gas testing of engineering controls (example:ANSI/ASHRAE 110 fume hood testing) and transmis-

sion routes (example: exhaust reentry into buildingsupply systems).

The first step in the assessment is to identify whatchemical(s) can be released including normallyuncharacterized byproducts. After characterizing theinherent hazard potential (largely based on physicalproperties, toxicity, and routes of entry), the next stepis to ascertain at least qualitatively, the release "pic-ture." At what points within the "control zone" willchemicals be evolved and at what release rate? Willthe chemical release have velocity? How has themaximum credible accidental release been accountedfor? Finally, how many employees are/could beexposed and what means are available for emergencyresponse?

Due to the high cost of ventilation, the choice of hoodand specification of airflow rates should be scrutinizedto ensure adequate protection at minimum flow.



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2.4.2 “Programming” and ControlObjectives for New Construction,

Renovation, or Program Evaluation

The following items shall be considered anddecisions made regarding each element's rel-evance following the hazard assessmentprocess:

• Acceptable exposure concentrations• Adequate workspace,• Air cleaning (exhaust pollution controls),• Air supply diffusers and discharge tem-

perature,• Alarm system (local and central monitor-

ing),• Commissioning (level of formality to be

applied),• Containment (tracer gas containment

"pass" criteria – e.g., AI 0.5, AI 0.1, AI0.05, etc.),

• Decommissioning,• Design sash opening and sash configura-

tion (e.g., for laboratory fume hoods),• Differential pressure and airflow between

spaces and use of airlocks, etc.,• Diversity factor in Variable Air Volume

(VAV) controlled laboratory chemicalhood systems,

• Exhaust discharge (stack design) anddilution factors,

• Face velocity for laboratory chemicalhoods,

• Fan selection,• Frequency of routine performance tests,• Hood location,• Manifold or individual systems,• Redundancy and emergency power,• Recirculation of potentially contaminated

air,• Preventive maintenance, and• Vendor qualification.

Programming is a term commonly used in the context ofa construction project whereby the needs of a usergroup are developed into the intended deliverables ofthe project. The idea here is that various scientific dis-ciplines have different needs in terms of ventilation.

Sets of design "templates" exist based on various typesof laboratories. While the characterization of laborato-ries by "organic chemistry, analytical chemistry, biology,etc.," are generically understood by most designers,knowledge of the chemistry and biology and, therefore,potential hazards, are generally beyond the knowledgebase of most designers.

The overall goal of providing a safe workspace for theend users can be greatly enhanced by the use of a haz-ard assessment and system design team.

Quality of system design and quality of performanceare enhanced by utilizing the most appropriate skillsand resources available to an organization. TheLaboratory Ventilation Management Plan shoulddescribe specific responsibilities for each departmentinvolved in the design, installation, operation, and useof ventilation systems (Table 1 provides some guid-ance.)



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Table 1. Major Responsibilities Recommended for Ensuring an Effective LVMP

Party Responsibility

Employer, Management,Owner, etc.

• Allocate sufficient resources.• Coordinate activities.• Ensure proper personnel training to design, install, commission,

maintain and use exposure control devices and ventilation systems.• Implement the plan, do, check, act concepts prescribed in environment,

health and safety management systems.• Provide leadership.• Remove barriers between departments.

Laboratory User

• Indicate and report performance problems.

• Provide information on potentially hazardous materials.• Provide information on procedures, work habits, duration of use,changes in hazardous operations and materials, etc.

• Utilize laboratory hoods in accordance with operating requirements andsafety guidelines.

• Work with Environmental Health and Safety to ensure appropriatesafety systems.

Environment Health andSafety

• Assist laboratory users with recognition and evaluation of hazards.• Conduct routine safety audits.• Determine suitable control strategies.• Establish control objectives and safety requirements.• Maintain records of performance.• Provide training for users of laboratories.

Engineering

• Analyze design options in consideration of hazard assessment findings.• Ensure system capability to provide safe, dependable and efficient

operation.• Ensure proper design, installation, and commissioning of systems.• Maintain up-to-date system documentation.

Maintenance

• Conduct preventive maintenance and repair.• Ensure proper functioning of systems.• Ensure system dependability.

Purchasing • Ensure equipment is not purchased without EHS approval.

Space Planning• Ensure safety and engineering issues are considered in any space

allocation decisions.

Note to Table 1: The responsible person could be from any one of the above parties.



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2.5 Recordkeeping

Complete and permanent records shall be main-tained for each laboratory ventilation system.

Records shall include:

• As-built drawings;• Commissioning report;• Equipment replacement or modifications

Testing and Balance reports;• Inspection and routine test reports;• Periodic performance and operation

reports• Maintenance logs;• Reported problems;• System modifications, and

• Written Laboratory VentilationManagement Plan.

3 Laboratory Fume Hoods

Only permanent records will allow a history of the sys-tem to be maintained.

Records should be maintained to establish a perfor-mance history of the system that can be used to opti-mize operation. Records should be kept for at least thelife of the system or until the system is altered.

A laboratory fume hood is a box-like structure with typ-ically one open side, intended for placement on a table,bench, or floor. The bench and the hood may be oneintegral structure. The open side is provided with asash or sashes that move vertically and/or horizontallyto close the opening. Provisions are made for exhaust-ing air from the top or back of the hood and adjustableor fixed internal baffles are usually provided to obtainproper airflow distribution across the open face.

Other terms used for a fume hood include laboratoryhood, laboratory chemical hood, and fume cupboard.

Although not technically correct, the term fume, asused today and historically in the context of definingfume hoods; includes both gases (vapors) andaerosols (i.e. particulates, mists, fumes, smoke, etc.).

Laboratory fume hoods are often appropriate foraerosol applications. However, because of the internal

turbulence, particulates, mists, etc., can deposit on theinterior surfaces. For certain applications, this may pre-clude the use of a fume hood.

Fume hoods have been a major tool in laboratory ven-tilation. However, a fume hood is not universally applic-able to all situations. In many cases, an enclosing hood(e.g., glovebox, biosafety cabinet, ventilated enclosure)



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3.1 Design and Construction

The design and construction of laboratoryfume hoods shall conform to the applicableguidelines presented in the latest edition ofACGIH ® Industrial Ventilation: A Manual of Recommended Practice for Design , and themost current codes, guidelines, and standardsand any other applicable regulations and rec-ommendations (see Appendix 2).

or a local exhaust hood (snorkel, tight fitting canopyhood, or specially designed hood) may provide as goodor better control and require less volumetric flow.

It is the intent of the standard to establish design para-meters and performance criteria without limiting newand innovative designs.

Although construction varies among models and man-ufacturers, the following are recognized as good designfeatures:

• Airfoils or other designs that reduce leakage and

airflow eddies at the front edge of the work areashould be provided at the front edge of the bench.Airfoils should not interfere with the hood’s abilityto meet the criteria of performance testing definedin this standard.

• Airfoils, beveled edges or other sidewall designthat reduces leakage and airflow eddies at theside walls should be provided at the side posts.

• Baffle design should provide for the capture ofmaterials generated within the hood and distributeflow through the opening to minimize potential forescape.

• Cupsinks should be protected by having a verticallip around the sink’s circumference of at least ¼ in.(0.635 cm) or eliminated if not needed.

• Utilities (e.g., valves and switches) should belocated at readily accessible locations outside thehood. If additional utilities are required, other thanelectrical, they may be located inside the hoodprovided they have outside cutoffs and can beconnected and operated without potentially sub-

jecting the hood operator to exposure from mate-rials in the hood or other unsafe conditions.

• Work surfaces should be recessed at least ¼ in.(0.635 cm) below the front edge of the bench or

surface; sides and back should be provided with aseamless vertical lip at least ¼ in. (0.635 cm) highto contain spills. However, excessively deeprecesses can increase the turbulence at the worksurface and induce reverse flow.



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3.1.1 Sashes

The laboratory fume hood shall be equipped witha safety-viewing sash at the face opening.

Sashes shall not be removed when the hood is inuse.

3.1.1.1 Design Opening

The design opening of a laboratory hood is theopen area at the face of the hood, which thedesign team assumed when determining the ven-tilation requirements of the exhaust system.

Where the design sash opening area is less thanthe maximum sash opening area, the hood shallbe equipped with a mechanical sash stop. Ameans of communicating when openings are inexcess of the design sash opening area shall beprovided.

The Chemical Hygiene Plan shall clearly instructthe hood users to position the sash so that theopening is no greater than the design openingwhile using the hood for protection.

Sash-limiting devices (stops) shall not beremoved without resizing or redesigning theexhaust system if the design opening is less thanfull opening.

Typical sashes available include the following:

• Combination vertical raising and horizontalsliding sashes,

• Horizontal sliding sashes, and• Vertical raising sash or sashes.

Refer to Figure 1 for diagrams of different sash con-figurations.

Sashes should be constructed of transparent shat-terproof material suitable for the intended use. Theforce to open the sash shall be reasonable for thesize and weight of the sash. Typically, a five foothood with a vertical rising sash should require

approximately five pounds of force to operate thesash. An additional one pound of force may berequired for each additional linear foot of fume hoodwidth. The sash should remain stationary whenforce is removed unless automatic closing to thedesigned operating sash opening is required.

The responsible person, or the design team, shoulddetermine the design opening of the hood and theposition of the sash-limiting device based on theneeds of the hood user. Operating the hood with alarger opening than the design opening results in areduced capture velocity (face velocity) and maysignificantly and adversely affect the performanceof the hood. Administrative controls, training,mechanical sash stops, alarms or other means areimportant for ensuring that the fume hoods andexhaust systems can provide the protection forwhich they were designed. Operating the sash at anincorrect position can jeopardize the protection oth-erwise afforded the hood users and those in theadjacent area.

The Chemical Hygiene Plan should indicate theproper circumstances for overriding the sash stop.



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3.1.1.2 Vertical Sashes

Vertical sashes shall be designed andoperated so as not to be opened more than

the design opening when hazardous mate-rials are being used within the hood

3.1.1.3 Horizontal Sashes

Horizontal sashes shall be designed so asnot to be opened more than the designopening width when hazardous materialsare being generated in the hood.

3.1.1.4 Combination Sashes

If a combination sash provides horizontallymoving panels mounted in a frame thatmoves vertically, the above requirements inSections 3.1.1.2 to 3.1.1.3 shall apply.

The vertical raising sash can usually be opened for full-face opening in the open position. If this is greater than the

design opening, control at the full open position may becompromised.

The horizontal sash should be designed to allow freemovement of the sash. Accumulation of debris or othermaterials in the sash track can impede movement. Thesash track can be designed to minimize this potential byhanging the sash from overhead. In any event, periodicmaintenance is recommended to ensure proper sash man-agement.

If three or more sash panels are provided, one panelshould be no more than 14 in (35 cm) wide if it is to serveas a safety shield narrow enough for a person to reacharound to manipulate equipment.

Caution is advised when using a horizontal panel as ashield in front of the hood operator as high concentrationscan accumulate behind the sash panel and escape alongthe Users’ arms protruding through the opening or escapewhen their arms are withdrawn.

A combination sash has the advantages and disadvan-tages of both types of sashes. The combination verticalraising and horizontal sliding sash, commonly referred toas a combination sash, is a combination of the verticalsash described in Section 3.1.1.2 and horizontal sash inSection 3.1.1.3. The combination sash may be raised to fullvertical sash opening. In the closed vertical position, thehorizontal sliding panels can be opened to provide accessto the interior hood chamber. Care should be taken indetermining the design opening of a combination sash.Remember to include the area beneath the airfoil sill and

through the bypass if one exists.



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3.1.1.5 Automatic Sash Closers

All users shall be trained in good work prac-tices, including the need to close the sash

when not in use.

All users of VAV systems shall be trained inthe proper uses of the sash, the energy con-sequences of improper use, and the need toclose the sash when the operation does notrequire its use.

Automatic sash positioning systems shall haveobstruction sensing capable of stopping travelduring sash closing operations without break-ing glassware, etc.

3.2 Laboratory Fume Hood Types

3.2.1 Auxiliary Supplied Air Hoods

Auxiliary air hoods have a portion of the totalvolume of exhausted air provided through aplenum located above and outside of the hoodFace.

Auxiliary air hoods shall meet the require-ments in Section 3.3.

The supply plenum shall be located externallyand above the top of the hood face.

The auxiliary air shall be released outside thehood.

The supply jet shall be distributed so as not toaffect containment adversely.

The auxiliary air shall not disrupt hood con-tainment or increase potential for escape.

Good work practice and energy stewardship (for VAVsystems) requires the user to close the sash when the

hood is not in use. A well implemented chemicalhygiene plan and proper administrative actions canensure that the sash is properly positioned. Monitoringof user compliance may be possible with some VAVsystems where the Building Automation System allowstrending of the sash position and feedback to manage-ment (and subsequently to the user.)

If the user feels it is his/her responsibility to close thesash and the culture is that they do close the sash, thenan automatic sash closer may not be necessary. On theother hand, if the user does not close the sash and man-agement tolerates this non-compliance, safety could be

jeopardized, energy consumption may increase and anautomatic sash closer may be advantageous.

With or without automatic closers, users should under-stand the importance of the closed sash, and integrateproper sash operation into work procedures.

Auxiliary supplied air hoods are not recommendedunless special energy conditions or design circum-stances exist. The information in this section is providedbecause many auxiliary air hoods are currently in use.The intent is not to discourage innovative design butcurrent experience indicates these requirements arenecessary.

The rationale for using auxiliary supplied air hoods isthat auxiliary air need not be conditioned as much (i.e.,temperature, humidity) as room supply air, and thatenergy cost savings may offset the increased cost ofinstallation, operation, and maintenance. However, if

not all the air from the auxiliary plenum is captured atthe hood face, the anticipated energy savings is notrealized. With respect to temperature and humidity,workers may experience discomfort if it is necessary tospend appreciable time at the hood.

If auxiliary air hoods are designed and operated prop-erly, worker protection at the face may be enhanced



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Figure 1 — Diagrams of different sash opening configurations.



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3.2.2 Bypass Hoods

Bypass hoods have a route for air enteringthe hood (the bypass mechanism) whichopens as the sash closes.

Bypass hoods shall meet the requirementsin Section 3.3.

The bypass mechanism shall be designedto minimize potential ejection of liquid orsolid material outside the hood in the eventof an eruption inside the hood.

because the downward airflow at the breathing zone sup-presses body vortices. However, if the design and opera-tion are improper, contamination control may be compro-mised. In addition, the air quality and condition inside the

hood may be significantly different from the room air andthese conditions may compromise the work conductedinside the hood.

For retrofit projects, auxiliary air may be installed morecheaply with less disruption than by upgrading the mainair supply system. If auxiliary air is conditioned to thesame extent as room air, most of the potential energyadvantages are lost while the disadvantages remain andthe total system becomes more expensive to install, oper-ate, and maintain.

With a worker (or reasonable proportioned manikin) at the

full open hood face, the hood should capture more than90% of the auxiliary jet airflow when either the auxiliaryair is at least 20°F (-6.7°C) warmer or cooler than roomair. This does not apply if the auxiliary air is designed tobe conditioned the same as room air.

Bypass mechanisms should be designed so the bypassopens progressively and proportionally as the sash trav-els to the full closed position. The face velocity at the hoodopening should not exceed three times the nominal facevelocity with the sash fully open. Excessive velocities,greater than 300 fpm (1.5 m/s), can disrupt equipment,materials, or operations in the hood possibly creating ahazardous condition.

The hood exhaust volume should remain essentiallyunchanged (


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3.2.3 Conventional Hoods

Conventional hoods shall meet the require-ments in Section 3.3.

3.2.4 Floor-Mounted Hoods

Floor-mounted hoods shall meet the require-ments in Section 3.3.

Conventional hoods have the hood exhaust volumeremain nearly unchanged as the sash position varies

from full open to the closed position.

However, as the sash is lowered, the face velocity willincrease. In the fully closed position, airflow would bethrough the airfoil only. With the sash par tially open, thehood will have very high face velocity.

Floor-mounted hoods are used when the vertical work-ing space of a bench hood is inadequate for the workor apparatus to be contained in the hood.

The base of the hood should provide for the contain-ment of spills by means of a base contiguous with thesidewalls, and a vertical lip sufficient to contain spillsinside the hood, often at least 1 in. (2.54 cm) or equiv-alent. The lip can be replaced by a ramp to allowwheeled carts to enter the hood. The hood should befurnished with distribution ductwork or interior baffles toprovide uniform face velocity.

Doors and panels on the lower portion should be capa-ble of being opened for the installation of apparatus.

If the lower doors are kept closed during operation, thehood and exhaust system design and operation may besimilar to a bench top laboratory fume hood and theeffectiveness of the control should be equivalent if all theprovisions of Section 3.3 are implemented. However, inmany floor-mounted hoods, the closed lower sash maycause significant turbulence and the hood may not per-form as well as a bench-top hood.

If the lower panels are opened during operations, thehood loses much of its effectiveness, even if face veloc-ities comply with Section 3.3.

The design and task-specific applications of floormounted (walk-in) hoods may make it difficult to complywith the work practices of Section 7 of this standard.



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3.2.5 Perchloric Acid Hoods

Perchloric acid hoods are specifically designedto safely handle certain types of perchloricacid work and shall be used for such work.

Perchloric acid hoods shall be used for han-dling anhydrous perchloric acid (> 85% con-centration.)

Hence, consideration should be given to preparationand implementation of written standard operating pro-cedures (SOPs) for use of floor-mounted hoods. Forexample, if manipulations below waist height are nec-

essary, special provisions may be necessary such asarmports or small openings strategically located at nec-essary access points.

Small rooms with one wall constituting a supply plenumand the opposite wall constituting an exhaust plenumshould not be called a floor-mounted hood. In suchinstances, workers are intended to be inside the hoodand exposure control provisions are drastically differ-ent. This standard does not apply to such rooms.

Perchloric acid is a strong acid, distinguished by thefact that it is the only mineral acid that is not constitut-ed as a gas dissolved in water. As a result, the vaporphase above a solution of perchloric acid is devoid ofperchlorate at temperatures below about 150°C. Its oxi-dation power is readily controlled by management ofconcentration and temperature, factors conducive to itsuse both as a process reagent and a catalyst.

Perchloric acid digestions and other procedures per-formed at elevated temperatures should be done inperchloric acid hoods.

Aqueous solutions of perchloric acid – The vapor pres-sure of 72% perchloric acid at 25°C is 6.8 mm Hg. Forcomparison sake, the vapor pressure of 70% nitricacid, a more widely used acid, is 49 mm Hg at 20°C.This simply means that the nitric acid would evaporatefaster. When a bottle of 70% perchloric acid is merelyopened, it cannot evaporate quantities presenting arisk of making contact with incompatible organic com-pounds.



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All procedures conducted in a perchloric acidhood shall be reviewed by the responsible personand immediate supervisor.

All procedures using a perchloric acid hood shallbe performed by trained personnel, knowledge-able and informed about the hazards and proper-ties of these substances, provided with appropri-ate protective equipment after suitable emer-gency contingency plans are in place.

The design of a perchloric acid hood shallinclude:

• All inside hood surfaces shall use materialsthat will be stable and not react with perchlo-ric acid to form corrosive, flammable, and/or

explosive compounds or byproducts.• All interior hood, duct, fan, and stack sur-

faces shall be equipped with water wash-down capabilities.

• All ductwork shall be constructed of materi-als that will be stable to and not react withperchloric acid and/or its byproducts and willhave smooth cleanable seamless joints.

• No part of the system shall be manifolded or joined to non-perchloric acid exhaust sys-tems.

• No organic materials, including gaskets, shallbe used in the hood construction unless theyare known not to react with perchloric acidand/or its byproducts.

• Perchloric acid hoods shall be prominentlylabeled “Perchloric Acid Hood, OrganicChemicals Prohibited.”

Perchloric acid hoods shall be periodicallywashed down thoroughly with water to remove allresidues in the hood, duct system, fan, and stack.

The process of diluting 60–70% perchloric acid orhandling dilute aqueous solutions of perchloric acidat room temperature presents little hazard of accu-mulating pure perchloric acid in hood ducts.

The institutional/corporate responsible person (e.g.,Safety Officer/Chemical Hygiene Officer) should benotified before procedures requiring a perchloricacid hood are performed.

The complications of wash-down features and cor-rosion resistance of the exhaust fan might beavoided by using an air ejector, with the supplierblower located so it is not exposed to perchloricacid.

The frequency of wash down depends on the pro-cedures inside the hood. Many procedures requiredaily wash down



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3.2.6 Variable Air Volume (VAV) Hoods

VAV hoods shall meet the requirements inSection 3.3

Variable exhaust flow from a laboratory hoodhas implications for room ventilation which shallbe addressed according to Section 5.

Additional commissioning requirements are nec-essary for these systems (See Section 6).

3.3 Hood Airflow and Monitoring (Design

and Performance Specifications)

3.3.1 Face Velocity

The average face velocity of the hood shall besufficient to contain the hazardous chemicals forwhich the hood was selected by following guid-ance in Section 2.4 and as generated under as-used conditions.

An adequate face velocity is necessary but is notthe only criterion to achieve acceptable perfor-mance and shall not be used as the only perfor-mance indicator.

Hood containment shall be verified as appropri-ate for the hazard being controlled (See Section

2.1.1).

The VAV hood is a conventional hood equipped witha VAV control system so designed that the exhaust

volume is varied in proportion to the opening of thehood face.

VAV controls applied to by-pass hoods have beennoted in many facilities. These situations appear to bedesign errors as VAV controls applied to by-passhoods largely defeats the purpose.

It is recommended that VAV hoods be equipped withemergency overrides that permit full design flow evenwhen the sash is closed.

Face velocity had been used historically as the prima-ry indicator of laboratory hood performance for sever-al decades. However, studies involving large popula-tions of laboratory fume hoods tested using a contain-ment-based test like the ANSI/ASHRAE Standard110, “Method of Testing the Performance ofLaboratory Fume Hoods,” reveal that face velocityalone is an inadequate indicator of hood performance.

In one published study, approximately 17% of thehoods tested using the method had "acceptable" facevelocities in the range of 80–120 fpm, but "failed" thetracer gas containment test with control levelsexceeding a control level of 0.1 ppm. Some of thesetests were “As Installed” while others were “As Used.”

See Section 6 on commissioning and routine perfor-mance testing for additional information.

Exposure assessments involve industrial hygienemeasurement of actual exposure potential to chemi-cals being worked with. This is accomplished throughair sampling in the breathing-zone of hood user.

Design face velocities for laboratory fume hoods in therange of 80 –100 fpm (0.40 – 0.50 m/s) will provideadequate face velocity for a majority of fume hoods.



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Containment must be verified quantitatively inthis range and compliance with use restric-tions, etc. enforced.

Factors including the design of the hood, the laborato-ry layout, and cross-drafts created by supply air andtraffic all influence hood performance as much as ormore than the face velocity.

Tracer gas containment testing is a reliable method forevaluating hood containment and is recommended incommissioning or in further applications as needed.

Most tracer gas containment test methods, includingthe ANSI/ASHRAE 110 “Method of TestingPerformance of Laboratory Fume Hoods” have certainlimitations that must be observed. The ANSI/ASHRAE110 method is a static test, under controlled conditions,and at low face velocities [


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3.3.2 Laboratory Hood Minimum Flow Rate

The flow rate of Constant Volume hoods and theminimum flow rate of Variable Air Volume hoodsshall be sufficient to prevent hazardous concentrations of contaminants within the laboratoryfume hood.

In addition to maintaining proper hood facevelocity, laboratory hoods shall maintain a mini-mum exhaust volume to ensure that contami-nants are properly diluted and exhausted from ahood.

The following considerations shall be taken into

account (as applicable) when setting the mini-mum hood flow rate for each hood:

• Control of ignition sources within the hood(a),• Design of the hood, the materials used in

the hood and the anticipated maximum gen-eration rates(a),

verified. Proper operator training and enforcement ofadministrative controls are still highly recommended.This is the range recommended for a majority of lab-oratory fume hoods.

100–120 fpm (0.50 –0.60 m/s): This velocity rangehas similar characteristics as 80 –100 fpm (0.40 –0.50m/s) but at significantly higher operating costs.Containment may be slightly enhanced in this rangeand hoods that do not contain adequately in the80 –100 fpm (0.40 –0.50 m/s) range may be improvedby operating in this range.

120 –150 fpm (0.60 –0.75 m/s): Although most hoodscan operate effectively in this range, performance is notsignificantly better than at the lower ranges of 80 –100fpm (0.40 –0.50 m/s) and 100 –120 fpm (0.50 –0.60 m/s).

The operating cost penalty imposed by high face veloc-ities in this rage is severe. Consequently, the high facevelocities are not recommended.

>150 fpm (>0.75 m/s): Most laboratory experts agreethat velocities above 150 fpm (0.75 m/s) at thedesign sash position are excessive at operating sashheight and may cause turbulent flow creating morepotential for leakage.

(a) A specific concern when choosing to minimize hood flow rates is the potential for fire or explosion if an ignition source were to exist within a vapor’s

lower and upper flammable or explosive limits.

Scenarios that could generate vapors in suchquantities include:

• Flammable liquids spill onto the work surface, or• Flammable vapors or gases released by any

other means.

Before selecting the minimum flow rate the usershould calculate the maximum credible concentra-

tion that might be reached at locations where an igni-tion source may be present. Assign a minimum flowrate or other control measure capable of maintainingthis concentration at the chosen safety factor per-centage of the LFL for the materials used. Typicallycited percentages range from 10% to 25% of the LFL(LEL). This calculation should be made for any newmaterials introduced for which the previous calculation



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• Potential for increased hood interior corro-sion. (b)

• Effect on exhaust stack discharge velocity (c),• Fume hood density (d),

• Need to affect directional airflows (e), and the• Operating range of the hood exhaust equip-

ment and the associated control system. (f)

may not address (e.g., a flammable material with ahigher generation rate or lower LFL.)

A small body of empirical research and theoretical

calculations(1–7) supports a range of values for theminimum flow for spill conditions and situationsinvolving the use of typically used quantities of sol-vents. At least two empirical studies measured con-centrations of contaminants resulting from simulat-ed chemical spills in a hood. Their conclusionsregarding minimum flow rate for the scenarios theystudied, correspond roughly to the high and lowends of the range mentioned below in the brief dis-cussion on energy savings. Additionally, extensiveexperience in Europe on European hood designsusing European hood testing procedures providesome support for the low end of the range.

Designers may choose to increase minimum hoodflow rates in order to maintain flammable vapor ductconcentrations below code required levels (SeeSection 5.4.1).

(b) A secondary concern involves the potential forcorrosion of the hood interior from the use of highlycorrosive operations* that may dictate the use of afume hood minimum flow rate near the higher endof the recommended range.

(c) As stated in the exhaust stack discharge sectionof this standard, exhaust fan systems typically havesome minimum design exhaust stack velocity. Theminimum flow rate selected for the hood may affectdesign and operation of the exhaust system.Designers need to coordinate these issues.

(d) In situations where the minimum hood flow dri-ves the airflow rate for the laboratory, the minimumflow affects energy consumption. A higher value forthe minimum flow requires more power to move andcondition the air. Depending on the airflow ratesinvolved, this situation occurs usually when the

hood density exceeds values in the range from 2%to 10% of the floor space in the room. (For exampleone or more 30x72 inch bench top fume hoods in a750 ft2 (75 m2) lab.) In situations where some otherconsideration sets the flow rate for the room, theminimum hood flow does not affect energy use.



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Ventilation system designers shall coordinate theoperating range of the fume hood flow rate withthe operating ranges of the other air supply andexhaust devices in the room.

Where attempting to save energy in typically higherhood density installations, minimum fume hood flowrates in the range of 150 to 375 hood air changesper hour (ACH) have been used to control vapor

concentrations inside hood interiors.(1–7)

Minimum hood flow rates might be selected withinthe above range if the user complies with provisionsin the left hand column. An exception being where awritten hazard assessment indicates otherwise.

(e) Designers may choose to increase minimum hoodflow rate if the ventilation equipment and the airflowcontrol system cannot regulate room air flows at thevalues required to effectively pressurize the room(See Section 5.2.1).

(f) The expression “within the operating range”includes accuracy expectations at the minimum hoodair change rate selected to prevent hazardous con-centrations* of contaminants within the hood: +/- 10%.

---------------------------------------------------

If a hood is taken completely out of service, the flowmay be reduced further or shut off so long as otherventilation needs are unaffected.

For the purposes of establishing a value for the internalvolume of the hood used in determining the flow ratecorresponding to the desired value of hood air changesper hour, the internal hood volume is approximated andhereby defined as the total internal hood work surfacearea times the internal height of the hood.

Section References

1. Sharp, G.P.: “A Review of U.S. and EuropeanEmpirical Research, Theoretical Calcula-tions, and Industry Experience on FumeHood Minimum Flow Rates.” InternationalInstitute of Sustainable Laboratories (I2SL)E-Library, http://www.i2sl.org/elibrary/

index.html, 2009.2. Braun, K.O. and K.J. Caplan: “Evapora-

tion Rate of Volatile Liquids, Final Report,2nd edition. EPA Contract Number 68-D8-0112”, PACE Laboratories Project890501.315. Washington, D.C.: U.S. Dept.of Commerce, NTIS, December 1989.

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3.3.3 Flow-Measuring Device for Laboratory

Fume Hoods

All hoods shall be equipped with a flow indicator,flow alarm, or face velocity alarm indicator to alertusers to improper exhaust flow.

The flow-measuring device shall be capable ofindicating that the air flow is in the desired range,and capable of indicating improper flow when theflow is high or low by 20%.

3. Klein, R.C., C. King, and P. Labbie: Solventvapor concentrations following spills in labo-ratory chemical hoods. Chem. Health Safe.11(2) :4–8 (2004).4. Harnett, P.B.: Empiri-

cal data and modeling of a flammable spillin a chemical fume hood do not support theneed for fire suppression within the chemi-cal fume hood ductwork. Chem. Health Safe. 10(4) :11–14 (2003).

5. Parker, A.J. and P.J. DiNenno: “Evaluationof Fixed Extinguishing System Effective-ness in Continuously Exhausting ChemicalFume Hoods.” Prepared for Merck & Co. byHughes Associates, September 2001.

6. Labconco Corp.: Development of the Lab-conco Protector ® Xstream ® High Perfor-mance Laboratory Fume Hood. Kansas

City, MO: Labconco Corporation, 2009.7. Ventilation Test according to DIN 12 924

Part 1: Fume Cupboard DIN 12 924 TA1500 x 900 – 900, Fume hood Test reportby Waldner Laboreinrichtungen GmbH &Co. for mc6 - Bench Mounted Fume Cup-board: Test Report No.159, May 2000.

The purpose of the flow-measuring device is to pro-vide the hood user with continuous informationabout the hood’s airflow. One method is to measurethe total volume flow through the hood. Anothermethod is to measure the face velocity.

One popular method for measuring total volumeflow is the Hood Static Pressure measuring device(See ACGIH’s ® Industrial Ventilation: A Manual of Recommended Practices for Operation and Maintenance ), which can be related to flow. Thismethod measures static suction in the exhaust ductclose to the hood throat and, if there are noadjustable dampers between the hood and themeasuring station, is related to the flow volume.

Other methods include various exhaust volume orflow velocity sensors.

The means of alarm or warning chosen should beprovided in a manner both visible and audible to thehood user. The alarm should warn when the flow is20% low, that is, 80% of the set point value.



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4 Other Containment Devices

4.1 Gloveboxes

4.1.1 General Description and Use

Gloveboxes shall not be used for manipulationof hazardous materials with the face or otherpanels open or removed nor with the glovesremoved.

If the potential combinations of material prop-erties with planned manipulations are so com-plex the hazard cannot be estimated, a glove-box may or may not be suitable. A hazard eval-uation shall be employed in such complexcases.

Gloveboxes shall be used when the propertiesof the hazardous materials, the planned manip-ulations, or a credible accident would generatehazardous personal exposures if the workwere done in an ordinary laboratory hood.

4.1.1.1 Location

There are no special requirements for locationbeyond those already noted for hoods.Gloveboxes shall be located as dictated by

workflow, space requirements and other needswithin the laboratory.

Tissue paper and strings do not qualify as the solemeans of warning.

Some manufacturers may require calibration that is

more frequent.

If gloves are removed it is not a glovebox but becomesa special enclosure requiring evaluation of effective-ness of containment.

Laboratory-scale gloveboxes, for which this standardapplies, should have a maximum internal chamber vol-ume of 50 ft3 (1.4 m3) (single-sided access) or 100 ft3

(2.8 m3) (double-sided access) respectively (pass-through chambers excluded). Larger gloveboxes mayoccasionally be found in laboratory settings but arebeyond the scope of this standard. For additional guid-ance, see the latest edition of the American GloveboxAssociation Society’s standard for additional adviceGuideline for Gloveboxes (AGS-G001.)

Gloveboxes may be used for any laboratory manipula-tions that can be conducted under the restraintsimposed by working with gloves through armholes.

Gloveboxes may be used when the manipulated sub-stances must be handled in a controlled (e.g., inert)atmosphere or when they must be protected from theexternal environment.

Glovebox containment is unaffected by airflow crossdrafts which create challenges for open face hoods.

Since manipulations through glove ports are somewhatdifficult, however, it is advisable to avoid high trafficareas and to allow ample aisle space.



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4.1.2 Design, Construction, and Selection

A hazard assessment as required in Section2.4 shall be done to select the appropriate

glovebox.

Positive pressure gloveboxes shall not be usedwith hazardous materials without a written riskassessment.

Interior cracks, seams, and joints shall be elim-inated or sealed.

4.1.3 Utilities

Utility valves and switches shall be in confor-mance with applicable codes. When control ofutilities from inside the glovebox is required,additional valves and switches shall be provid-ed outside the glovebox for emergency shutoff.

4.1.4 Ergonomic Design

Ergonomics shall be a significant considerationin the design, construction, and/or selection ofgloveboxes. Frequency of use shall dictate theextent to which ergonomic principles will beapplied. Proper application of ergonomic princi-ples shall be met by referring to the latest edi-tion of, Guideline for Gloveboxes, AGS-G001.

Depending upon the nature of the hazard controlled, aglovebox may be constructed of material with favorable

characteristics such as fire rating, radiation shielding,nonporous and/or impervious surfaces, corrosion-resistance for the intended use, and easily cleaned.Interior corners should be covered.

For additional guidance see:

STANDARDS OF PRACTICE FOR THE DESIGN ANDFABRICATION OF GLOVEBAGS(AGS-G002)

STANDARDS OF PRACTICE FOR THE APPLICA-TIONS OF LININGS TO GLOVEBOXES(AGS-G003)

STANDARDS OF PRACTICE FOR THE SPECIFICA-TIONS OF GLOVES FORGLOVEBOXES (AGS-G005)

STANDARDS OF PRACTICE FOR THE DESIGN andFABRICATION OF NUCLEAR APPLICATION GLOVE-BOXES (AGS-G006)

Certain applications require that all valves be locatedinside of the glovebox containment and all lines exteri-or to the box be 100% welded.

Frequent use versus infrequent use may dictate theextent to which ergonomics principles will be applied.



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4.1.5 Provision for Spills

The design of the glovebox shall provide forretaining spilled liquids so the maximum vol-

ume of liquid permitted in the glovebox will beretained.

A system for draining the spilled liquid into asuitable sealed container shall be provided ifthe properties of the spilled liquid or other cir-cumstances prevent cleanup by workingthrough the gloves.

4.1.6 Exhaust Ventilation

Containment gloveboxes shall be providedwith exhaust ventilation to result in a negative

pressure inside the box that is capable of con-taining the hazard at acceptable levels.

Gloveboxes shall be exhausted to the outsideunless the provisions described in ANSIStandard Z9.7 and Section 5.3.6.2 of this stan-dard are met.

4.1.7 Exhaust Air Cleaning

The air or gas exhausted from the gloveboxshall be cleaned and discharged to the atmos-phere in accordance with the general provi-sions of this standard and any pertinent envi-ronmental regulations.

Air-cleaning equipment shall be sized for themaximum airflow anticipated when hazardousagents are exposed in the glovebox and theglovebox openings are open to the extent per-mitted under that condition.

If the air-cleaning device (ACD) is passive (i.e.,a HEPA filter or activated carbon) provisionshall be made for determining the status of the

ACD, as noted in Section 9.3. If the ACD isactive (i.e., a packed-bed wet scrubber),instrumentation shall be provided to indicateits status.

The ACD shall be located to permit ready accessfor maintenance. Provision shall be made formaintenance of the ACD without hazard to

See Sections 4.1.11 through 4.1.14 for ventilation rec-ommendations for specific glovebox types.

If the glovebox is sealed tightly when closed, a pres-sure relief valve might be required to prevent excessivenegative pressure in the glovebox, depending on thechoice of air-cleaning equipment and exhaust blower.

Any ACD should be selected and applied according tothe manufacturer’s specifications, with attention to air-flow rate, and other operating parameters that canaffect performance for the contaminants of interest.

The ACD should be located as close as is practical tothe glovebox to minimize the length of contaminatedpiping or the need for maintaining high transport veloc-ity.



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personnel or the environment and so as not tocontaminate the surrounding areas.

4.1.8 Exhaust Ducting

Exhaust piping shall be in accordance with theprinciples described in the latest editions of theACGIH ® Industrial Ventilation Manual,ANSI/AIHA ® Z9.2, and the ASHRAEHandbook Fundamentals. All piping within theoccupied premises shall be under negativepressure when in operation.

Materials shall be resistant to corrosion by theagents to be used.

4.1.9 Monitoring and Alarms

A glovebox pressure monitoring device with ameans to locally indicate adequate pressurerelationships to the user shall be provided onall gloveboxes.

If audible alarms are not provided, documentedtraining for users in determining safe pressuredifferentials shall be required.

Pressure monitoring devices shall beadjustable (i.e., able to be calibrated if not a pri-mary standard) and subject to periodic calibra-tion at least annually.

4.1.10 Decontamination

A written decommissioning plan followingthe procedures outlined in the latest edi-tion of ANSI/AIHA ® Z9.11 LaboratoryDecommissioning shall be developed.

Before the access panel(s) of the glovebox areopened or removed, the interior contamination

shall have been reduced to a safe level.

If the contaminant is gaseous, the atmospherein the box shall be adequately exchanged toremove the potentially hazardous gas. This canbe affected by exhausting the box through itsventilation system, and where necessary pro-viding an air inlet that is filtered if required.

Ergonomics principles indicate that the total numberand types of alarms should be minimized.

Alarms should be clearly distinguished from eachother.

Safe level is relative to the contaminant involved.Analytical techniques for determining surface contami-nation (mass/unit area, counts per minute/unit area)are helping to provide increasingly sensitive but notalways specific risk information. Correlating surfacecontamination with exposure potential remains more ofan art than a science.

Use caution if gases or vapors may condense ordeposit on surfaces. Decontamination may still berequired.



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If the contaminant is liquid, any liquid on sur-faces shall be wiped with suitable adsorbentmaterial or sponges until visibly clean anddry. Used wipes shall be placed in a suitable

container before being removed from theglovebox.

If the contaminant is a powder or dust, all inter-nal surfaces shall be cleaned and wiped untilvisibly clean. The exterior surfaces of thegloves also shall be wiped clean.

Precautions to prevent hazards to personneland contamination of the premises shall bemade if the ducting is to be opened or disman-tled.

If there is any uncertainty about the effective-ness of contamination reduction procedures,personnel involved in opening the panels ofthe glovebox

ansi aihaz9.5 2012(laboratoryventilation)

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