toxic gas user's handbook
TRANSCRIPT
STANFORD UNIVERSITYENVIRONMENTAL HEALTH & SAFETY
TOXIC GAS USER'S HANDBOOK
A GUIDE TO THE IMPLEMENTATION OF THE
TOXIC GAS ORDINANCE
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CREDITS Toxic Gas User's Handbook was developed by the Department ofEnvironmental Health and Safety (EH&S) at Stanford University. Pleasedirect all questions and comments to EH&S at 723-0448.
Revised December, 1997
The TGO User's Handbook is available from the EH&S Home Page(http://www.stanford.edu/dept/EHS)
G:/EHSDept/Cox/TGO/TGO Manual 1297/TGO_1297.doc
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C ONTENTSCHAPTER ONE Introduction to Toxic Gas Ordinance .....................................................................4
1.1 Background .........................................................................................................41.2 Levels of Regulation............................................................................................41.3 Acute vs. Chronic Toxicity...................................................................................5
CHAPTER TWO General Requirements.............................................................................................7Table 1. Toxic Gas Ordinance General Requirements .................................................8Table 2. Toxic Gas Ordinance Responsibility Matrix..................................................9
CHAPTER THREE Regulated Materials ..............................................................................................103.1 Regulated Toxic Gas Table ................................................................................103.2 Hazardous Materials Not Regulated by the TGO.................................................113.3 Chemical Safety Database..................................................................................113.4 Does the TGO Apply to Your Research? ............................................................123.5 Classification Process and Calculations ..............................................................133.6 TGO Classifications...........................................................................................143.7 Minimum Threshold Quantities Per Control Area ...............................................153.8 Exempt Quantities Per Vessel ............................................................................163.9 Maximum Threshold Quantities Per Vessel ........................................................163.10 Criteria to Operate as a TGO Limited-Use Laboratory.......................................17Flowchart 1, 2, 3, and 4 ...........................................................................................18
CHAPTER FOUR Purchase, Procurement & Return of Toxic Gases.................................................224.1 Before Purchasing a Toxic Gas ..........................................................................224.2 Determining Availability, Size, and Cost ............................................................234.3 Purchasing a Toxic Gas......................................................................................234.4 Delivery of a Toxic Gas .....................................................................................244.5 Return of Toxic Gas Cylinders ...........................................................................24
CHAPTER FIVE Transportation and Handling ...............................................................................255.1 Receiving Toxic Gases from the Vendor.............................................................255.2 Transporting a Toxic Gas Cylinder or Lecture Bottle ..........................................255.3 Placing a Toxic Gas Cylinder into Service ..........................................................26
CHAPTER SIX Toxic Gas Use ........................................................................................................276.1 Gas Cabinets, Fume Hoods and Ventilated Enclosures........................................276.2 Cylinders...........................................................................................................276.3 Security .............................................................................................................286.4 Fire Extinguishing Systems................................................................................296.5 Self-Contained Breathing Apparatus...................................................................29
CHAPTER SEVEN Control Requirements ...........................................................................................30Table 3. TGO Minimum Control Requirements ........................................................32
CHAPTER EIGHT Storage of Toxic Gases ..........................................................................................338.1 Storage Parameters ............................................................................................338.2 Compatibility of Materials .................................................................................338.3 Storage Requirements ........................................................................................34
CHAPTER NINE Emergency Preparedness and Response ...............................................................369.1 Emergency Response.........................................................................................369.2 Emergency Preparedness & Response Plans .......................................................369.3 Emergency Drills Every Three Months...............................................................37
CHAPTER TEN Permitting..............................................................................................................3810.1 Compliance Plan..............................................................................................3810.2 Partial Gas System Upgrades............................................................................3810.3 Closures of Facilities........................................................................................39
CHAPTER ELEVEN Laboratory and Research Facilities Standard ......................................................4011.1 Material Classification ....................................................................................4011.2 Cylinder Size...................................................................................................4011.3 Storage ............................................................................................................4011.4 Notification .....................................................................................................4011.5 Systems, Equipment and Processes...................................................................4111.6 Practical Difficulties ........................................................................................42
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1 INTRODUCTION TO TOXIC GAS ORDINANCE
I N T R O D U C T I O N This section summarizes the Toxic Gas Ordinance (TGO) and itsrelevance to research activities at Stanford University.
1.1 Background In September 1990, Santa Clara County adopted the Toxic Gas
Ordinance (TGO) to prevent, control and respond to potentially
dangerous conditions related to toxic gases and to protect the public from
acute exposure due to “accidental releases” of toxic gases. The TGO
governs the storage, use and manufacturing of regulated materials in
greater than specified threshold quantities. In addition, it contains
specific provisions mandating engineering controls, protective
equipment, storage requirements, emergency response plans, warning
systems and employee training based on the type and quantity of toxic
gas used.
1.2 Levels of Regulation The TGO establishes three levels of regulation regarding laboratory use
of toxic gases:
Level 1 – Exempt
Not regulated by the TGO, but must meet hazardous materials
handling policies and regulations as stated in the Stanford Safety
Manual.
Level 2 – TGO Limited-Use Laboratory
Limited to laboratory and research experiments, which meet the
TGO Standard for use of small quantities of gas in research for
limited periods of time.
Level 3– Full TGO Compliance
Materials whose quantities and duration of use require operation
within the full TGO and Uniform Fire Code (UFC).
If your activity uses a gas that may be regulated under the Santa Clara
County TGO, please access the TGO Web page at the Laboratory Health
and Safety Programs Web page from the EH&S Home Page
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(http://www-leland.stanford.edu/dept/EHS/) to start your evaluation.
Follow the hyperlinks until you have determined if the gas is regulated
or unregulated. If it is regulated, then make a determination as to
whether you can meet the requirements for a Limited-Use Laboratory
Notification. Otherwise, you must complete a Permit Form. This
Handbook and all forms are available from the TGO Web page.
If you have a question regarding the use of the Handbook, accessing the
TGO Web page, or completing the forms, please contact the Stanford
University Chemical Hygiene Officer or Certified Industrial Hygienist or
tel: 723-0448.
1.3 Acute vs. ChronicToxicity
The TGO classifies chemicals according to their toxicity into four
categories: Class I, Class II, Class III, and Non-Regulated (NR), with
Class I being the most toxic. The TGO specifies basic requirements for
all regulated materials. However, materials stored in quantities below the
specified threshold quantities are not required to meet Class I, II, or III
controls.
The TGO is to be used in conjunction with the most current UFC,
Uniform Mechanical Code (UMC), and Uniform Building Code (UBC),
all of which regulate the storage and use of hazardous chemicals. If
provisions within the codes, county ordinances, or Federal or state
regulations or laws overlap or conflict, the most stringent requirements
will prevail.
The TGO is intended to protect the public from acute exposure to toxic
gases. Acute exposure is short-term, immediately apparent contact with a
substance that has potentially dangerous effects on human health. The
basis for determining the toxicity of gases in the TGO is the Level of
Concern (LOC) which is based on the Immediately Dangerous to Life
and Health (IDLH) values. When the IDLH is not available, the LethalConcentration 50% (LC
50) or the Lethal Concentration Low (LCLo) is
used. All of these values measure the short-term effects of large
quantities of material based on experimental data. The LC50
is the median
lethal concentration at which fifty percent of test animals die when
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exposed to the particular gas concentration by inhalation. The LCLo is
the lowest dose of a particular gas concentration at which test animals
die following exposure.
On the other hand, chronically toxic materials have adverse effects on
human health resulting from low dose exposures over an extended period
of time. Air quality regulations and Occupational Safety and Health
Administration rules address both chronic and acute exposure. Many
materials can have acute and chronic effects while some are primarily
one or the other. Fortunately, at Stanford, toxic gases are used in
quantities and with control measures that result in exposure levels lower
than the minimum levels for chronic exposure.
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2 GENERAL REQUIREMENTS
I N T R O D U C T I O N This section states the fundamental requirements for use of toxicgases and refers to other sections of the Handbook for additionalinformation.
The TGO specifies certain general requirements that must be met in
order to use toxic gases. A compliance plan, stating how the University
planned to meet the requirements, was submitted on September 18, 1991.
Permits are issued at the expense of the department that uses toxic gases.
(See Section 10.0, Permitting)
The TGO requires that no one store, handle, dispense or use regulated
materials in a manner which causes or poses a significant risk of an
“unauthorized discharge.” An unauthorized discharge is a release such as
pouring, emitting, or spilling a regulated material into the environment
via sewers, air, storm drains, lakes, sidewalks or streets without a permit
to do so.
Table 1 lists the general requirements of the TGO intended to decrease
the risk of an unauthorized discharge. Table 2 provides a matrix of
operating and maintenance requirements and responsibilities based on
the TGO general requirements. For additional information about these
topics, refer to the indicated section(s).
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TABLE 1TOXIC GAS ORDINANCE
GENERAL REQUIREMENTS
GENERALREQUIREMENTS
APPLICABILITY RELEVANT HANDBOOKSECTION(S)
Seismic Bracing All stationary tanks and pipingsystems
6.0 Toxic Gas Use;7.0 Control Requirements
Security All facilities secured againstunauthorized entry
6.0 Toxic Gas Use
Breathing Apparatus Two SCBA for all Class I gases &Class II corrosives
9.0 Emergency Preparedness andResponse Procedures
Reduced/Restricted FlowOrifices/Valves
Any amount ofClass I greater than the LOC
7.0 Control Requirements
Separation of Incompatible Materials All regulated material 8.0 Storage
Leak Testing All containers upon arrival and at timeof removal
5.0 Transportation and Handling
Protective Plugs and Caps All regulated material 5.0 Transportation and Handling;6.0 Toxic Gas Use
Emergency Response Plans, Team,and Drills
All facilities with regulated materials 9.0 Emergency Preparedness andResponse Procedures
Fire Extinguishing System All facilities with regulated materialand any Class I greater than the LOC
6.0 Toxic Gas Use
Annual Maintenance All control devices 7.0 Control Requirements
Exhausted Enclosure All regulated material 6.0 Toxic Gas Use
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TABLE 2TOXIC GAS SYSTEMS OPERATION, MAINTENANCE AND FUNDING GUIDELINES
These are recommended guidelines for operation, maintenance and funding for toxic gas cabinets andsystems. These guidelines can be used as a point of reference for toxic gas facilities on campus.
GAS CABINET ENGINEERING CONTROL COMPONENTS RESPONSIBLEDEPARTMENT
Facilities Lab
1. Independent Exhaust Ventilation: This includes gas cabinets, fume hoods, or otherapproved exhaust enclosures exhausted to a treatment system.
X
2. Unauthorized Discharge Treatment System to 0.5 IDLH: This criterion is based onthe maximum release rate for a single cylinder or the maximum release rate formanifolded cylinders.
X
3. Dedicated Inert Gas Purge (N2): Responsibilities include the funding of the N2 usedfor the purging of secondary containments. Does not include the N2 required forchanging cylinders (part of cabinets) or the N2 used for other purposes.
X
4. Signage Compliant to UFC 79-3 X
5. Compatible and Durable Primary Piping X
6. Welded Piping Connection X
7. Secondary Containment Piping: Required only for Class I and Class II corrosivegases if not in compatible piping material.
X
8. Flow Restricting Orifice or Limiting Device: All portable tanks and cylinders mustbe marked to indicate the orifice (inches) on the certification tags and the vesselthemselves.
X
9. Excess Flow Controls, Regulators, CGA and Process/High Pressure Vent Valves:Excess flow control valves must be permanently marked indicating the maximumdesign flow rate at STP (UFC Article 80). The gas manifold, pigtail, diaphragmregulator, valves and gauges are part of the gas delivery system.
X
10. Temperature Control System X
11. Automatic Shutoff Valve X
12. Emergency Alarm Devices X
13. Emergency Power X
14. Gas Detection System at PEL: Automatic shutdown is required upon gas detection ator above the PEL in occupied areas and at or above one-half the IDLH in unoccupiedones.
X
15. Local Gas Shutoff: This includes the Emergency Shutdown Switches (ESS) mountedon the cabinets, room or corridors that are designed to shutoff the gases in case ofemergency. Manual valves are part of the delivery system and the responsibility of thelabs.
X
16. Seismic Shutoff Valve: Automatic shutoff is required for all Class I and II toxic gassources in the event of seismic activity with a peak acceleration of 0.3 g or greater.
X
17. Emergency Control Station: This part of the system includes the EmergencyManagement Control System (EMCS), Base-10, fire protection panel and the 24-hrmonitoring provided by EMCS or Forsythe.
X
18. Fire Extinguishing System X
19. EMCS and Around-The-Clock Alarm Monitoring X
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3 REGULATED MATERIALS
I N T R O D U C T I O N This section describes the resources and methods for determiningwhat requirements must be met in order to use a toxic gas atStanford. The TGO regulates toxic gases based on their toxicity,volatility and quantity.
Ask yourself the following four questions to determine what
requirements of the TGO, if any, must be met to use a particular gas:
• Is the material a compressed gas or is it used or handled like a
compressed gas?
• Based on its toxicity and volatility, is the material exempt from TGO
requirements?
• Are toxic materials present in excess of a threshold quantity and, if
so, what controls are required?
• Does the toxic material use meet "Limited-Use Laboratory”
requirements under the TGO and thereby eligible for regulatory
relief?
• Can the material be used in a diluted concentration that exempt it
from the TGO or make some controls unnecessary?
Several resources – the Regulated Toxic Gases Table, Non-Regulated
Toxic Gases Table, the Chemical Safety Database, and Material Safety
Data Sheets (MSDS) – provide data to answer the questions. This
chapter discusses these resources followed by an in-depth explanation of
how to answer the four questions. The Department of Environmental
Health & Safety (723-0448) is available to assist in answering these
questions.
3.1 Regulated Toxic GasTable
The Regulated Toxic Gases Table is a valuable and quick reference for
information about toxic gases. The Regulated Toxic Gases Table
contains information such as the TGO class of a gas, IDLH, Material
Hazard Index (MHI), Permissible Exposure Limit (PEL), and the
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maximum percent of a toxic gas in a mixture with non-toxic gas(es) that
is exempt from the TGO. If a compound is listed in the Regulated Toxic
Gases Table, further investigation is necessary to determine what TGO
requirements must be met to use the material at Stanford.
3.2 Hazardous Materials NotRegulated by the TGO
The Non-Regulated Toxic Gases Table contains a list of those chemicals
that are not subject to TGO regulations. EH&S evaluated these materials
and found them not to meet the criteria for regulation by the TGO.
Nonetheless, the materials not regulated by the TGO must meet all other
relevant hazardous materials policies and regulations discussed in the
Stanford Safety Manual.
3.3 Chemical Safety Database EH&S maintains a Chemical Safety Database which includes
information about the hazards of chemicals used at Stanford. The
Database contains the TGO class, the known hazardous properties and
some physical properties (e.g., melting point, boiling point, and flash
point) of chemicals used at Stanford, as well as a list of regulations
which pertain specifically to each chemical.
The Chemical Safety Database can be accessed on the Web, Forsythe, or
Folio or by obtaining a PC version from EH&S (723-0448). Accessing
the Chemical Safety Database from Forsythe or Folio involves the
following simple steps:
1. Log on to Forsythe or Folio.
2. For Prism access: At the “>” prompt type:
Prism sel Chem Safety
For Folio access: At the “>” prompt type:
Folio sel Chem Safety
3. Read the pertinent information from the Database’s first menu.
4. To find out the hazardous properties of a particular substance, type
“Find” and then the name of the chemical or compound for which
you are seeking information. In Folio you can also type “browse,”
which allows you to selectively scan the listed chemicals.
5. Follow the directions given in the menus.
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You can search for hazardous materials by full or partial name, Stanford
number, Chemical Abstracts Services (CAS) number, or phonetic name.
3.4 Does the TGO Apply toYour Research?
Question #1: Is the material a compressed gas or is it used orhandled like a compressed gas?
The TGO only regulates materials that are used as gases. Flowchart #1
illustrates the process to determine if a material is considered a gas, and
thereby, could be subject to TGO regulations. If a material (i.e., solid or
liquid) becomes or acts as a gas at standard temperature and pressure and
is shipped in a compressed gas cylinder, TGO regulations apply to the
material. In addition, if a material is used or handled as a gas, it is
thereby regulated by the TGO.
The Regulated Toxic Gases Table lists chemicals that may be used as a
gas. However, if a material is listed as a liquid and is not used as a gas, it
is not regulated by the TGO. Note that all chemicals, whether regulated
by the TGO or not, must comply with all other relevant policies and
regulations for the use of hazardous materials. For more information
regarding other requirements, see the Stanford Safety Manual.
Question #2: Based on its toxicity, volatility, and concentration, isthe material exempt from the TGO requirements?
The TGO classifies all materials by toxicity and volatility using the
Level of Concern (LOC) and/or Material Hazard Index (MHI) to
determine the required level of control. (Use Flowchart #2 to determine
if a material is toxic and volatile enough to be regulated by the TGO.)
The National Institute for Occupational Safety and Health (NIOSH) is
the primary source of IDLH data for determining the MHI.
Materials less than the LOC are not regulated by the TGO. Poison A
materials greater than the LOC and other materials with an MHI greater
than or equal to 4,900 are regulated by the TGO. The Regulated Toxic
Gases Table lists the MHI and corresponding classification of regulated
gases at critical percentage if in a mixture with non-toxic gas(es). In
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addition, the table lists the critical percentage of a toxic gas in a mixture
with non-toxic gas(es) that is not regulated (NR) by the TGO because the
overall MHI of the mixture is less than 4,900.
As stated above, the TGO does not regulate materials listed in the Non-
Regulated Toxic Gases Table. For materials not on either list, EH&S
(723-0448) will determine the MHI and classification for the material.
3.5 Classification Process The equation for the MHI of a single chemical is:
Equation 1 MHI (dimensionless) = Equilibrium Vapor Pressure (EVC)
Level of Concern (LOC)
where: EVC (ppm) = (Vapor Pressure @ 25°C) x 106
Atmospheric Pressure
LOC (ppm) = (0.1)(IDLH)
The Equilibrium Vapor Pressure (EVC) is the state of the regulated
substance when the vapor pressure has stabilized at 25°C. The Level of
Concern (LOC) is the maximum airborne concentration of a substance
that will not cause serious harm to the majority of the population when
exposed for a relatively short period. The LOC for an individual gas is
defined as 10% of the Immediately Dangerous to Life and Health(IDLH) value. The EVC, LOC, IDLH, LC
50, LCLO and other toxicity
information for many materials can be found in the Chemical Safety
Database and/or the TGO Gases Database.
Combining the above equations into one simple equation for calculating
MHIs (at atmospheric pressure of 760 mm Hg) results in the following
equation:
Equation 2 MHI=13,158VP
IDLH
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To determine the MHI for a mixture, an IDLH for a mixture is firstcalculated in one of the following two ways:
Equation 3 For a mixture with only one (1) toxic component,
MHIm1 = 13,158VPi x fi
IDLH
where fi = mole (or weight) fraction of the toxic gas
Equation 4 For a mixture with two (2) or more toxic components,
n
MHImi = 13,158 33 VPi x fi
i=1 IDLHi
Note: IDLHi is the IDLH of the ith toxic component of the mixture.
If the 0.1 IDLH (LOC) for a material has not been established, then0.01 LC
50 or 0.1 LCLo is substituted. The MHI for a mixture indicates
whether the toxic material is regulated by the TGO. These formulas
clearly illustrate that using a dilute mixture of toxic gas with a non-toxic
gas lowers the overall MHI. The Regulated Toxic Gases Table lists the
critical concentration of toxic gas in a mixture with non-toxic gas(es)
that exempt the toxic gas from the TGO. The vast majority of mixtures
on the Stanford campus are composed of one toxic and one non-toxic
gas, which makes this calculation fairly straightforward. In all, a dilute
mixture is not only safer in the laboratory, but may also be exempt from
TGO requirements.
3.6 TGO Classifications The TGO sets forth the following criteria to determine the class of a
particular substance or mixture:
• Class I: MHI equal to or greater than 500,000 or a DOT Poison A*• Class II: MHI equal to or greater than 10,000 but less than 500,000• Class III: MHI equal to or greater than 4,900 but less than 10,000
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*Note: Although the Department of Transportation (DOT) eliminated the
Poison A classification, it was the TGO's intent to categorize Poison A
gases as Class I gases. Hence, pure gases listed in the Regulated Toxic
Gas Table with an “A” designation next to the TGO class continue to be
regulated by the TGO's requirements for Poison A gases, i.e., Class I.
Question #3. Is there toxic material in excess of a threshold quantityand, if so, what controls are required?
For laboratories using very small quantities of toxic gases, the TGO
contains exemptions or less stringent controls. (See Flowchart #3 on the
opposite page to determine the control requirements for regulated
materials.) Laboratory buildings, which do not store more than the
Minimum Threshold Quantities (MinTQ) of toxic gases within a
specified “control area,” are subject only to the general obligations of the
TGO and MinTQ Controls. (See Section 7.0 Control Requirements). The
UFC defines a control area inside a building as a space bounded by a
1-hour fire-resistive occupancy separation and/or exterior wall, roof or
foundation of a building.
Contact the Stanford Fire Marshal (725-0609) to find out what
constitutes a control area in your building. To determine the use of toxic
gases in a control area, consult the building Hazardous Materials
Management Plan (HMMP) (See Stanford Safety Manual) kept by each
department's administrator or safety representative. Contact EH&S (723-
0448) if you cannot locate the HMMP for your building.
3.7 Minimum ThresholdQuantities Per Control Area
MinTQs are based on the aggregate weight of the regulated material
within a control area. The MinTQ is defined as follows:
For DOT Poison A: 1 lb For other regulated material: 2 lb
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3.8 Exempt Quantities PerVessel
Facilities may be exempt from most provisions of the TGO if the
aggregate quantity of the material in a control area does not exceed the
MinTQ’s and the quantity in any single experimental vessel does not
exceed the following criterion:
DOT Poison A: 0.25 lb
All other regulated material: 1 lb
3.9 Maximum ThresholdQuantities Per Vessel
If the quantities of a Class II or Class III material in a single vessel is
greater than the Maximum Threshold Quantity (MaxTQ), then the Class
of the material will be increased by one level, e.g., a Class II material
will become Class I.
The MaxTQ is calculated as follows:
Maximum Threshold Quantity (lb) = 2.5 x 108
MHI
Currently, no quantities of gases exist on campus in excess of their
Maximum Threshold Quantities.
Question #4. Does the toxic material use meet “Limited-Use
Laboratory” requirements under the TGO, thereby making it
eligible for some regulatory relief?
The Laboratory and Research Facilities Standard for Toxic Gas
Ordinance Compliance was developed to mitigate the hazards associated
with the use of small quantities of gas in research for limited periods of
time.
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3.10 Criteria to Operate as aTGO Limited-Use Laboratory
Use Flowchart #4 to determine if a laboratory may operate as a TGO
Limited-Use Laboratory. To operate under the Laboratory and Research
Facilities Standard, the following criteria must be met.
1. The laboratory and research experiments do not simulate nor are part
of a production process.
2. Gas cylinders are small in size and never exceed 15 lb of liquefied
gas or 340 scf at NTP. EXCEPTION: Class 1 and Poison A gases
never exceed 20 scf at NTP.
3. Experiments are limited to 30 consecutive days.
4. All experiments are conducted in an approved exhausted enclosure.
5. The regulating agency is notified at least three (3) working days
before any experiments begin.
In Chapter 11, Laboratory and Research Facility Standard for Small
Cylinder Gas Use, the Standard is presented in full.
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4 PURCHASE, PROCUREMENT & RETURN OF TOXIC
GASES
INTRODUCTION This section runs through the procurement process for toxic gases at
Stanford. Toxic gas purchases are made through Central Stores
using the PRISM system. Praxair is the University’s sole vendor for
toxic gases. Toxic gas cylinders and bottles will be directly delivered
to and picked up from the laboratory by Praxair. This system is
designed to support faculty in their goal to maintain compliance in
their laboratories.
Using toxic gases in the laboratory is a high-risk activity for two reasons.
First, the hazards of toxic gases are very dangerous to life and health.
Second, the regulations regarding toxic gases are strict, and non-
compliance offers the potential for large penalties. For these reasons, the
University has established a program in cooperation with Praxair for
procuring toxic gases. By following the guidelines of the program, the
user, the responsible faculty, and the University will be more aware and
able to manage the risks associated with toxic gases.
4.1 Before Purchasing a ToxicGas
Each person who purchases a toxic gas must obtain authorization from
EH&S. A Toxic Gas Purchase Authorization Form may be obtained by
calling EH&S (723-0448). The Authorization Form must be signed by a
principal investigator and the toxic gas user, and then returned to EH&S.
Before purchasing a toxic gas, always ask yourself these questions (using
Section 3.0 Regulated Materials and reference tables for guidance):
1. Can I use a less toxic gas?
2. Can I use the toxic gas in a dilute concentration exempting it from
the TGO or moving it to a lower MHI class?
3. Can I purchase a smaller quantity? (See Section 8.0 Storage and p. 4-
4 in the Stanford Safety Manual for sizing suggestions.)
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4. Can I use it in an amount at or below its MinTQ or exempt quantity?
5. Is my lab or area fully prepared to receive this gas?
4.2 Determining Availability,Size, and Cost
Information about the toxic gases which are readily available (from
Praxair) through Stanford University’s Central Stores may be found in
the SNAP Stores Catalogue located in PRISM accessed as follows:
1. Logon to Forsythe.
2. At the “Command>” prompt type: Prism
3. At the “Your Response:” prompt type: Select SNAP Stores
4. Browse through the catalogue by following menu directions.
If the gas or mixture required is not in the Central Stores Catalogue, call
Praxair Customer Service (1-800-660-2066) to specify your needs and
request the faxing of necessary information to Central Stores. Central
Stores will give the gas a stock number and enter the information into its
Catalogue. This process takes no more than 48 hours and will often
occur overnight. The gas will then become part of the Stores Catalogue
and in the future Praxair will not need to be called before each purchase.
4.3 Purchasing a Toxic Gas Before attempting to order toxic gases, proper authorization from EH&S
is necessary. (SNAP will not allow you to place an order without
authorization). Follow these steps to purchase a gas:
1. Logon to Forsythe.
2. At the “Command>” prompt type: Prism
3. At the “Your Response:” prompt type: Select SNAP Purchasing
4. Enter your Stanford PIN number as requested and follow directions.
5. Change requisition type to STO.
6. Use general ledger (gl) code 94632 with your account number.
7. If required, order a restricted flow orifice. (See Section 7.0
Control Requirements)
After an order has been placed, Praxair will send an acknowledgment via
e-mail to the person who placed the order. An expected shipment date
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will be included in the acknowledgment. Delivery is guaranteed within
10 days, but will usually be within 2 to 4 days. Rapid Purchase Orders
(RPOs) may not be used for toxic gas purchases.
4.4 Delivery of a Toxic Gas Praxair will stop at the Stores Warehouse to affix, and subsequently,
scan a bar-code record, establishing that the toxic gas has arrived on
campus. In most cases, the toxic gas will then be delivered directly to the
laboratory. Praxair delivers toxic gases Monday through Friday as long
as an authorized purchaser is available at the time of delivery.
4.5 Return of Toxic GasCylinders
To return “empty” Praxair cylinders, simply call Praxair Customer
Service (1-800-660-2066) with your purchase order number to schedule
a cylinder pick-up. On the date of retrieval, the Praxair representative
will pick up the empty cylinder, and then stop at the Stores Warehouse to
have the cylinder’s bar code scanned to verify that it has been removed
from campus. To remove cylinders not purchased via the Praxair system,
call EH&S’ Chemical Waste Group at 723-0448.
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5 TRANSPORTATION AND HANDLING
INTRODUCTION This section illustrates safe procedures for moving and handling
toxic gas cylinders. Issues such as inspecting cylinders for leaks,
using appropriate carts when transporting toxic gas cylinders, and
keeping caps on cylinders when not in use are discussed.
5.1 Receiving Toxic Gasesfrom the Vendor
All toxic gas cylinders must be visually inspected and leak tested by the
receiving party upon vendor delivery. Cylinders that leak or do not pass
inspection should not be accepted from the vendor. The inspection and
leak testing process includes the following:
• Ensure that the cylinder valve protection and dust caps are intact and
in place.
• Verify that the cylinder labels are legible and list the contents,
potential hazards, and precautions.
• Inspect the cylinder for excessive wear, rust or damage.
• Make certain that the cylinder hydrostatic test date has not expired.
• Using an appropriate gas detection system, leak test the cylinder to
check for gas leaks. If commercially available, handheld detectors
for a specific or class of gas should be used. (Snoop or other
materials that detect gas leaks may be used; however, Snoop has the
potential to contribute to the contamination of high purity systems.)
If a cylinder does not meet the criteria outlined above – especially if it is
leaking – refuse the delivery, and Praxair will take the necessary
protective action and remove the cylinder from Stanford property.
5.2 Transporting a Toxic GasCylinder or Lecture Bottle
In order to safely transport toxic gas containers, there are several general
guidelines to be followed:
26
• Only trained personnel can handle or transport gas cylinders and
lecture bottles.
• Carry small lecture bottles by hand one at a time or in a gas cylinder
carrier.
• Cylinders must be transported by at least two people using a sturdy
gas cylinder cart. The cart should be in good repair and have wheels
large enough to negotiate uneven surfaces without tipping or
suddenly stopping.
• Cylinders must be securely restrained on the cart.
• Cylinders must be transported with protective and dust caps in place.
• Cylinders cannot be rolled on their sides for any reason.
• Only for a short distance may cylinders be rolled on-end, e.g., from
the cart to the gas cabinet.
• Always treat cylinders as if they are full.
5.3 Placing a Toxic GasCylinder into Service
After a toxic gas cylinder or lecture bottle has been transported from the
dock to the laboratory, it must immediately be placed into a gas cabinet
or ventilated enclosure. Only individuals trained by the gas cabinet
vendor or experienced Stanford personnel can install or remove toxic gas
cylinders. Unless a department or laboratory has established its own
procedures, follow the instructions of gas cabinet manufacturers and
vendors for installing cylinders. If installation and removal instructions
from the gas cabinet vendor are unavailable, call Praxair (1-800-660-
2066) or EH&S (723-0448) to request information.
It is important that the Compressed Gas Association (CGA) fittings in
the gas cabinet match the cylinder. If the fittings do not easily go
together, the manifold is probably not the correct type for the gas type
and another manifold should be used. Never force the fittings onto the
cylinder.
However, lecture bottle valves do not have different outlets for different
types of gases. Therefore, to prevent cross contamination, mark
equipment and controls with the name of the gas being used.
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6 TOXIC GAS USE
INTRODUCTION This section explains the procedures and requirements for using
toxic gases in the laboratory. The discussion includes the use of gas
cabinets, gas cylinder safety, and security.
According to the TGO, toxic gases must be stored and used in an
exhausted gas cabinet, exhausted enclosure, or a separated ventilation
room.
6.1 Gas Cabinets, FumeHoods and Ventilated
Enclosures
If an exhausted gas cabinet, fume hood or ventilated enclosure is used,
the following requirements must be met:
1. An individual using the toxic gas must obtain thorough training from
the gas cabinet and equipment vendor or a person designated by the
faculty advisor.
2. A toxic gas cylinder and its dedicated inert gas purge cylinder should
be stored in the same gas cabinet or exhausted enclosure.
3. Cylinders in the cabinet shall be secured with chains at 1/3 and 2/3
their height.
4. All gas cabinets, in accordance with provisions of the current
Uniform Building Code (UBC), shall be seismically braced.
5. The exterior of the gas cabinet shall be labeled with the full chemical
name(s) of the toxic gas(es) including concentration(s).
6.2 Cylinders Follow these procedures when using gas cylinders:
• Investigate and thoroughly understand the physical and chemical
characteristics of the gas to be used.
• Verify that the DOT label is legible and that the full chemical name
(including mixture components and concentrations) is clearly visible
on the cylinder.
• Label all cylinders with their maximum flow rate. The maximum
28
flow rate for cylinders with reduced flow or excess flow valves will
be determined by the valve manufacturer or the gas supplier.
• Keep cylinders, valves, regulators free from oily or greasy
substances.
• Close cylinder or lecture bottle valves when not in use.
• Secure lecture bottles in a stand or similar device.
• Close valves on all cylinders that are being returned to the vendor
and indicate that the cylinder is “empty” by labeling it with the
initials “MT”.
• Regularly check cylinder for obvious signs of defects, deep rusting,
or leakage.
• Ensure that Material Safety Data Sheets (MSDS) are available to
personnel.
• If there is an accidental release of toxic gas, dial 9-911 and/or pull
the nearest fire alarm (See Section 9.0 Emergency Preparedness and
Response). If there is a non-health threatening, minor leak that is
contained in a ventilated enclosure or gas cabinet, report the leak to
EH&S (723-0448) and to Praxair (1-800-660-2066) to arrange for an
exchange of cylinders.
• Use experimental equipment suitable for the contents of the cylinder.
Materials of construction for experimental equipment should be able
to withstand the physical force of the pressure and the reactive
properties of the gas. Toxic gas vendors have specific information
regarding appropriate materials to be used with specific toxic gases.
6.3 Security Any laboratory that uses toxic gases must be secured against
unauthorized entry. Basic security measures can be accomplished by
having the laboratory building remain locked in the evening and on
weekends, or having the individual laboratories locked when no one is
working inside them.
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6.4 Fire ExtinguishingSystems
Any interior or exterior area in which regulated toxic gases are used
and/or stored must have an automatic fire sprinkler system. Sprinkler
systems need to be designed to specifications no less than those required
in UBC 38-1 for Ordinary Hazard Group 3. If you have any questions
regarding your fire extinguishing system, contact the Stanford Fire
Marshal at 723-0609.
6.5 Self-Contained BreathingApparatus
The TGO mandates that facilities with Class I or corrosive materials
must provide a minimum of two (2) Self-Contained Breathing Apparati
(SCBA) for use by fire fighters and other emergency response personnel.
The SCBAs, suitable for the materials in the laboratories, are maintained
on University emergency response vehicles.
At Stanford, Emergency Responders are equipped with their own
SCBAs. However, in some instances, additional SCBAs are needed to be
provided on site. It is dangerous and prohibited for an untrained
individual to use an SCBA. Individuals should only use an SCBA after
receiving medical approval, attending Stanford University's Respiratory
Protection Program (723-0448), and receiving SCBA training.
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7 CONTROL REQUIREMENTS
INTRODUCTION This section lists the toxic gas release controls required by the Toxic
Gas Ordinance. These controls include gas detection systems,
seismic protection, signs, and treatment systems, which limit exit
concentrations to one-half of the Immediately Dangerous Level to
Health (IDLH) values.
As explained in Section 3.4 (See Section 3 Regulated Materials),
the minimum control requirements vary for each class of toxic gas and
are less if the quantity does not exceed the Minimum Threshold Quantity
(MinTQ). It is the responsibility of the faculty researcher to assure that
the required controls are provided. The TGO Minimum Control
Requirements Table, that follows, lists the control requirements for each
class and quantity. For more information about each requirement or
assistance to develop a system to meet these requirements, contact
EH&S at 723-0448.
The TGO requires qualified personnel to test all control systems at least
annually and to maintain them in good working condition with
maintenance records and certifications available upon inspection or
request by the Santa Clara County Office of Toxics Enforcement.
The TGO mandates that gas cabinets have the following features:
• Self-closing limited access ports or fire-rated windows.
• Self-closing doors.
• Negative pressurization inside the cabinet relative to the surrounding
area.
• Face velocities on access ports greater than 200 fpm.
• At least 12-gauge steel construction.
• Treatment systems connected to the exhaust.
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In the event of an unauthorized discharge, the TGO requires that the
design of treatment systems meet the following criteria:
1. Reduced discharge concentration of a gas to one-half the IDLH.
2. Sized assuming a full cylinder with maximum flow rate.
The maximum flow rate of a vessel is calculated based on assuming total
release from the cylinder or tank within the time specified below:
CONTAINER NON-LIQUEFIED(min)
LIQUEFIED(min)
Cylinder 5 30
Portable Tanks 40 240
NOTE: Upon contact with moisture, halogenated, non-carbon based
gases can hydrolyze to mineral acids; and thus, the TGO requirements
for these gases (e.g., monitoring, treatment, and compatibility) also apply
to their decomposition products.
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TABLE 3TGO MINIMUM CONTROL REQUIREMENTS
ENGINEERING CONTROL REQUIREMENTEXEMPT
QUANTITY(see p. 16)
MINIMUMTHRESHOLDQUANTITY
(see p. 15)
CLASSIII
GAS
CLASSII
GAS
CLASSI
GAS
Independent Exhaust VentilationA X X X X
Unauthorized Discharge Treatment System to 0.5 IDLHB X X X X
Dedicated Inert Gas PurgeC X X X
Signage Compliant to UFC 79-3 X X X
Compatible & Durable Primary PipingD X X X
Welded Piping Connections X X
Secondary Containment PipingE C X
Flow Restricting Orifice/Flow Limiting DeviceF A A X X
Excess Flow ControlG X X
Temperature Control Systems X X
Automatic Shutoff valve X X
Emergency Alarm Devices X X
Gas Detection System at PELH A X X
Local Gas Shutoff X X
Seismic Shutoff ValvesI X X
Emergency Control System X
Fire Extinguishing System I I X
A =Required for DOT Poison A gasesI = Required for Class I gasesC = Required for Class II corrosive gases if not in compatible material piping.
A An Independent Exhaust Ventilation System is either an exhausted gas cabinet, exhausted enclosure, or a separated ventilation room. An "exhaustedenclosure" is an approved fume hood or process equipment exhausted to a treatment system, equipped with automatic sprinklers.
B Accounting for all engineering controls, the maximum release rate for a single cylinder is determined by the single worst case event from a singlecylinder while the maximum release rate for manifolded cylinders is the sum of the worst case release rates for all the cylinders.
C A Dedicated Inert Gas Purge System can be used to purge compatible gases. Gas Purge Systems must be in gas cabinets unless vacuum operated.D In all practical instances, primary piping must pass a Helium Leak Test of 10(-9) cc/sec. Refer to guidelines set forth by the National Association of
Corrosion Engineers to evaluate the compatibility of piping materials with the gas being converted.E If it can be demonstrated that equivalent protection exists (e.g., fail-safe-to-close valve activated by a loss in vacuum pressure and an alarm), then
secondary containment may not be required for systems operating at sub-atmospheric conditions.F All portable tanks and cylinders must be marked to indicate the orifice (inches) on the certification tags and the vessels themselves. The lettering
needs to be 1/4" high at a minimum and contrast to the color upon which it is printed.G Excess Flow Control Valves must be permanently marked indicating the maximum designed flow rate at STP (UFC Article 80).H Automatic Shutdown is required upon gas detection at or above the Permissible Exposure Limit (PEL) in occupied areas and at or above one-half the
IDLH in unoccupied ones.I Automatic Shutdown is required for all toxic gas sources in the event of seismic activity with a peak acceleration of 0.3g (2.94 m/s2) or greater.
33
8 STORAGE OF TOXIC GASES
INTRODUCTION This section states the parameters for storage of toxic gases at
Stanford. Storage of toxic gases is strongly discouraged. Only those
gases that are currently being used should be on campus.
8.1 Storage Parameters All regulated toxic gases must be stored and used in a ventilated gas
cabinet, exhausted enclosure, or a ventilated separate gas storage room
as defined by the UFC.
Only gases, which are currently being used, can be stored at Stanford.
Current usage of a toxic gas is generally defined as using or planning to
use the gas within one year. There should be no storage at Stanford of
toxic gases that are not currently being used. Gases that are not being
used should be returned to the supplier. Toxic gases that are kept for
more than one year can degrade, or the cylinder and connections can
degrade in such a way as to become very unstable and dangerous. In
general, all toxic gas cylinders should be returned to the vendor within
one year from the delivery date.
8.2 Compatibility ofMaterials
Incompatible classes of regulated materials must be separated by means
of 1-hour fire resistive construction, a gas cabinet, or a fume hood. If a
gas is stored by itself in a gas cabinet, the gas is automatically
considered separated from incompatible materials. However, if the gas is
stored in an exhausted enclosure with other substances, the additional
materials must be compatible.
Storage compatibility can be determined using Stanford’s Compatible
Storage Group system. Each chemical has been assigned a compatible
storage group identifier in the Stanford Chemical Safety Database:
34
A Compatible Organic Bases, Flammables, and Poisons
B Pyrophoric and Water-Reactive Materials
C Compatible Inorganic Bases, Oxidizers and Poisons
D Compatible Organic Acids, Flammables, and Poisons
E Compatible Oxidizers, Organic Peroxides and Acids
F Inorganic Acids not including Oxidizers
G Not Intrinsically Reactive or Flammable
J Poison Compressed Gases; not Flammable or Reactive
K Explosive or Other Highly Unstable Material
L Non-Reactive Flammables or Combustibles including Solvents
X Segregate from ALL Groups and from Each Other Individually
8.3 Storage Requirements Please note that only gases in the same storage group can be stored in the
same exhausted enclosure.
There are several ways to minimize both the quantity and the hazard of
toxic gases in a lab:
1. Use good procurement practices. Keep records of usage so that the
empty cylinder or other container can be picked up when the full
cylinder is delivered.
2. Always try to use the gas that has the lowest toxicity of the
alternatives available. Use a low concentration mixture of the gas
whenever possible. (See Section 3 Regulated Materials)
3. Minimize the quantity of toxic gases in the lab by ordering no more
than one year's supply. Storage of gases for more than one year
increases the hazard of the gases because the gas may become
unstable and more dangerous. In addition, the cylinder, lecture bottle
or connections and valves may become worn and subject to failure.
4. Balance the hazard of storing large quantities of a toxic gas with the
hazard of frequent turnovers when determining the quantity to
purchase. (See page 4-4 of the Stanford Safety Manual for guidance
on sizing cylinders for purchase.)
5. Order toxic gases in quantities that require reordering no more than
once every one to two months. Frequent bottle changes increase the
likelihood of leakage and exposure during the bottle changing
35
procedure and increase downtime of the experiment. Discourage
long-term storage in fume hoods. Do not store toxic gases in lab
bench drawers or cabinets.
6. Avoid exposing stored chemicals to heat above room temperature,
direct sunlight, or other radiant heat sources.
7. Provide for toxic gas storage space adequate to your lab’s research
needs.
8. Be sure all storage containers are clearly labeled with the name(s)
and hazardous properties of their contents.
9. If exterior storage is necessary, contact the Stanford Fire Marshal at
723-0609.
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9 EMERGENCY PREPAREDNESS AND RESPONSE
INTRODUCTION This section describes the procedures to be followed in case of anemergency. Other issues related to “unauthorized discharges” andemergency response are discussed.
9.1 Emergency Response Any unauthorized discharge of a toxic gas that is not a minor cylinder
leak in an exhausted gas cabinet or enclosure is considered health
threatening and immediate action is required:
1. Call 9-911 from a campus phone and/or pull the nearest fire alarm.
2. Contact the Principal Investigator (PI), lab director or other
responsible party.
3. If you know it is safe to do so, close the gas cylinder valves and turn
off other equipment or activate the shut-off sequence for the gas
cabinet.
4. Ensure that the door to the room or area where the release occurred
is closed after everyone is out.
5. Evacuate the building.
Toxic gas releases are considered health threatening and should always
be reported and treated with the utmost seriousness and concern for the
safety of other Stanford personnel, the community, and yourself. If there
is any question as to the level of hazard or seriousness of a situation,
leave the laboratory, call 9-911 and/or pull the nearest fire alarm. The
EH&S Emergency Response Team and Palo Alto Fire Department
maintain the capability to respond to toxic gas releases.
9.2 Emergency Preparedness& Response Plans
Each department has an Emergency Preparedness and Response Plan
outlining procedures for handling emergencies. If a department uses
toxic gases, a response plan for unauthorized releases of toxic gases must
be included in the building or department plan. Persons who use toxic
gases are responsible for the following:
37
1. Discuss with their co-workers the various scenarios for possible
releases of gases before there is an emergency.
2. Plan precise actions that will be taken in the event of a release.
3. Know the location of the following safety equipment:
• All manual shut-down devices
• The nearest phone at a safe location
• The nearest fire alarm
• The nearest evacuation door and route
4. Know how to use all shutdown devices and what doors need to be
closed to isolate the area.
9.3 Emergency Drills EveryThree Months
The TGO requires emergency response drills involving the on-site
response team to be conducted at least every three months. Drills are
conducted on a rotating basis at various campus facilities. Records of
drills for the past three (3) years are maintained at the Environmental
Safety Facility for review by the Palo Alto Fire Department or the Office
of Toxics Enforcement.
Your department's Emergency Response Plan, Stanford University's
Research Policy Handbook and the Stanford Safety Manual have more
information about emergency preparedness and response procedures.
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10 PERMITTING
INTRODUCTION This section explains the process of obtaining a permit for the use ofa toxic gas at Stanford University. All gases used in amounts andtypes classified by the TGO as either Class I, II, or III Toxic Gasesrequire permits in order to be used.
Unless you are able to design your work such that it is exempt from or
not regulated by the TGO, a compliance plan (Toxic Gas Installation
Application) must be submitted to the University’s Department of
Environmental Health & Safety and the Santa Clara County Office of
Toxics Enforcement (OTE). Upon acceptance of the compliance plan
and signing off on all aspects of it, the OTE will issue a permit for a fee.
All costs associated with implementing the compliance plan are the
responsibility of the faculty researchers and their respective department.
10.1 Compliance Plan Compliance plans should include Material Hazard Index (MHI)
calculations for each regulated substance that will be used in the facility
and any additional acute toxicity information supporting the MHI values;
maps of the building floor plan and emergency assembly alarm system,
automatic shutdown systems, Helium leak test, and gas monitoring
system; and specifications (cut sheets) for equipment such as gas
cabinets, seismic sensors, remote shutdown systems, emergency shut-off
valves, gas detectors, and emergency generators.
10.2 Partial Gas SystemUpgrades
The TGO states that partial gas system upgrades require permits. If a
building mechanical permit is required to modify the piping, then the
TGO mandates that the entire system be upgraded. On the other hand, if
a mechanical permit is not required for a piping modification – e.g.,
connecting an existing piping system to a new piece of equipment – then
the TGO does not require the entire system to be upgraded.
39
10.3 Closures of Facilities A facility regulated by the TGO cannot be abandoned or closed until a
closure plan has been submitted (through EH&S) and approved by the
OTE. A closure plan needs to be submitted by the responsible party to
the OTE at least 30 days before the facility's closure date. The plan needs
to illustrate to the OTE that regulated toxic gases that have been used,
stored, dispensed or handled in the facility will be transported, disposed,
or reused in a way conducive to public health and safety.
40
11 LABORATORY AND RESEARCH FACILITY STANDARD
INTRODUCTION In order to conduct research, it is often necessary to utilizehazardous gases in small amounts for short durations. PreviousToxic Ordinance Gas provisions did not allow the needed flexibilityfor the use of small quantities of hazardous gases over the exemptamounts. The intent of the Limited-Use Laboratory and ResearchFacilities Standard is to mitigate the hazards associated with the useof small quantities of gas in research for limited periods of time.
Scope The scope of this standard is limited to laboratory and research
experiments that do not simulate nor are part of a production process,
and which meet the following criteria. See Flowchart #4 for
determination of Limited-Use Laboratory. To use this standard, a
Limited-Use Laboratory Form must be completed and submitted to
EH&S.
11.1 Material Classification All gases shall be classified in accordance with the categories established
by the current California Fire Code (CFC) and the current Toxic Gas
Ordinance. When a conflict occurs, the more stringent classification shall
apply.
11.2 Cylinder Size Cylinders of hazardous gases shall be limited to less than 15 lb or 340
scf @ NTP. EXCEPTION: Class I and highly toxic gases shall be
limited to 20 scf at NTP.
11.3 Storage The experimental use shall be limited to 30 calendar days. All cylinders
shall be stored in approved occupancies in conformance with the
requirements of the TGO and CFC/CBC. All use and storage facilities
shall be fully sprinklered per the requirements of the CFC.
11.4 Notification Users shall notify the regulating agency at a minimum of three (3) work
days before any experimental use begins. Contact EH&S at 723-0448 for
assistance with the notification process.
41
11.5 Systems, Equipment andProcesses
1. Ventilation. All experimental use shall be in an approved exhausted
enclosure. Enclosures shall have sufficient ventilation to dilute the
worst-case release to a concentration less than 1/2 the IDLH at the
point of discharge to the atmosphere or be directed to an approved
treatment system.
2. Emergency Power. Ventilation systems shall be continuous and
shall be connected to emergency power, unless the system is
provided with an automatic shut off valve which positively shuts off
the gas cylinder in the event of lost ventilation.
3. Restrictive Orifice. All gas cylinders with gases having a vapor
pressure greater than 1 psig shall have a restrictive flow orifice
installed either by the vendor or immediately after delivery.
EXCEPTION: Lecture bottles and low vapor pressure gases may not
require an orifice.
4. Monitoring. All gas usage within the scope of the standard shall be
continuously attended or monitored with feedback to the required
fail/safe to close valve. Area and/or room monitoring shall be
provided when directed as necessary by an approved Certified
Industrial Hygienist (CIH). Monitoring instruments shall be provided
with emergency power. When required, monitoring alarm shall be at
the PEL or less. The alarm shall be audible outside the room of use.
5. Security. Each use area must be secured. "No Smoking" signs shall
be posted. All cylinders shall be checked for leaks during delivery
and prior to return to storage. Signage shall be provided outside the
room of use.
6. Pipe Valves and Fittings. All appurtenant pipes, valves and fittings
shall be suitable for the intended use and in conformance with all
requirements of the CFC. A fail/safe to close valve shall be provided
as close as practical to the gas cylinder. The valve may be either
pneumatic or approved electric type.
42
11.6 Practical Difficulties The jurisdiction is authorized to modify any of the provisions of this
standard upon notification in writing by the owner or a duly-authorized
representative where there are practical difficulties in carrying out any
provision of this standard, provided that the spirit of the standard shall be
complied with, public safety secured and substantial justice done.