icfo slides part 2

Copyright © Pro Laser 2005

Module 1Establishing safety in the workplace

Laser safety for safety supervisorsMike Green


Directives

Product Directives

ProductRegulations

User Guidelines Product Standards

Workplace Directives

WorkplaceRegulations

(legal)

The New ApproachDirectives

Workplacesafety

EN 60825-1: 1994Safety of laser productsPart 1 - Equipmentclassification,requirements and user’sguide

TR 60825-14: 2004Safety of laser productsPart 14 - A user’s guide

LEGAL

National implementation


Directives

Product Directives

ProductRegulations

User Guidelines Product Standards

Workplace Directives

WorkplaceRegulations

(legal)

The New ApproachDirectivesLEGAL

National implementation

Lase

r haz

ard

and

com

plex

ityDegree of control

Specificworking

code“shall”

Generaluserguidance“should”

Workplacesafety


Administration of safetyTR 60825-14

Safety responsibilities of employers and employees

• All users and supervisors have a role to play

• Employers responsible for assessing risksand reducing them to an acceptably low level

• Employer should establish a laser safetypolicy


Administration of safetyTR 60825-14

Safety responsibilities of employers and employees

• All users and supervisors have a role to play

• Employers responsible for assessing risksand reducing them to an acceptably low level

• Employer should establish a laser safetypolicy

Laser Safety Officer


Administration of safetyDelegationSafety responsibilities of

employers and employees

Laser Safety Officer• Employers must ensure LSO is competent

• Responsible for:• Day-to-day management

• Monitoring compliance

• Taking action where there isnon-compliance

• Approving procedures

• Maintaining recordsResponsibilities andauthority, in writing

Director

Division head

LSO

Laser User


Administration of safetyLSO

Documentation• Records of location and applications of all class3B and 4 lasers and control measures in place

• Written procedures

• Risk assessments and audit reports

• Laser safety training records (and plan forrefresher training)

• Copies of standards and guidance documents

• General site safety policy statement

• Laser safety policy statement

LSO Documents to hand

All records kept up todate and reviewedregularly


Maintenance of a safeworking environment

Inspection oflaser areas

Regular inspection oflaser facilities

Check list

Testing of controls

Key points to look for:

a) modifications, relocation or replacement of laserequipment;

b) changed conditions of use;

c) changes to the environment in which the laserequipment is used;

d) changes of personnel;

e) indications of any reduction in compliance withsafety procedures.


Incidents and accidentsKey information

Location of medicalcentre

Information on laserwavelength (“grab bag”)

Treat for shock

Laser users:• in the event of an accident or incident terminate

laser emission and report to management;

• Seek medical attention in the event of a real orsuspected laser injury.

LSO:• Possible eye-injured persons must be seen by a

qualified ophthalmologist within 24 hours of thepotential exposure;

• Investigate the circumstances and assess likelyexposure, document the conclusions of theinvestigation and review system of control beforelaser is permitted to be used.


Screening of laser workersEye tests

T

A S B T V S P F T L C K C

g f e v b p m k l m n o p o

Registered Class 3B and 4laser users should have:

• Effective use of botheyes.

• No visual defects thatcannot be correctedwith spectacles

• No untreated glaucoma.

“… routine ophthalmic examinations ofemployees… have no value as part of a health

surveillance programme”

Eye tests only make sensefor persons at risk ofexposure to Class 3B andClass 4 laser beams atwavelengths within theretinal hazard range.

Such persons wouldnormally be issued withlaser protective eyewear.


Procedures for laser use inthe research environment

StructureElements of procedures:

1. Essential generalinformation

2. Procedures foremergencies

3. Procedures fornormal operation

4. Procedures foralignment

5. Procedures forexternal contractors

Procedures should be written by the laser supervisorand approved by the LSO.

Copies may be issued to laser users, who should signto acknowledge receipt and that the procedures areunderstood.

Procedures should be reviewed regularly to ensuretheir continued relevance to requirements









Description and purpose of the equipment/process.

Type, approximate power and classification of lasers.

Drawing identifying the laser hazard area(s).

Listing of other hazards present with references tosafety codes.

Basic engineering and administrative controls.

PPE provided and storage point(s).

Contact details of LSO and responsible person.

Names of authorised laser users.









Action to be taken in the event of specified equipmentfailure or other emergencies

Incident reporting procedure and the action to be takenin the event of a suspected accident

A plan drawing of the laser area indicating the positionsof electrical isolation switches, fire extinguishers etc.

A list of hazards (especially for emergency services)









Point out basic good practice (e.g. terminating beams,secure fixing of turning mirrors)

Identify administrative controls and use of PPE.

Highlight any deviations from best practice.

The normal shut-down procedure should be described.

Include requirements for safety checks (interlocks etc.).

Servicing procedures should address the establishmentof temporary hazard areas, administrative controls,PPE and who should carry out the work. It shouldinclude procedures for controlling the work of outsideservice engineers e.g. permits to work.



Structure

Best practice

Elements of procedures:






Risk assessment

Procedures


Best practice in the researchenvironment

General userguidanceEngineering

controls

Administrativecontrols

Personalprotectiveequipment

Installed Engineering Controls

• Install interlocks on access points to(3B or 4) laser areas and connect to laser

• Enclose the beam path (and terminate)

• Make the laser beam path stable

• Minimise exposed shiny surfaces

• Beam at waist height and no chairs




controls



Installed aids to Administrative Control

• Check for appropriate knowledge andattitude of personnel and provide training

• Develop and document proceduresaddressing normal operation,maintenance and service activities

• Install warning lights and labels

• Provide beam visualisation equipment foruse with safety eyewear

• Control use of laser key switch




controls



Installed aids to PPE use

• Strict enforcement

• Suitable style(s) of eyewear

• Proper storage and labelling

• Regular inspection and maintenance


Risk AssessmentAll hazardsHazard

Risk

Injury

= S x A x E where :

S Severity of harm

A Probability of human access tothe hazard

E Probability of exposure whenhazard is accessible

potential to cause harm

likelihood of harm

LEGAL

Laser radiation

Electricity

Fire

Fume

High pressure gases

Mechanical

Solvents

Etc.


Risk AssessmentAll hazardsHazard

Risk

Injury

= S x A x E where :

S Severity of harm




likelihood of harm

LEGAL

Laser radiation

Electricity

Fire

Fume

High pressure gases

Mechanical

Solvents

Etc.


Risk AssessmentLaser radiationHazard

Risk

Injury


likelihood of harm

LEGAL

Output

Wavelength

Access to beam

Application

Environment

Personnel at risk

Etc.

= S x A x E where :

S Severity of harm




Laser Radiation RiskAssessment: Wavelength

Laser radiation

Output

Wavelength

Access to beam

Application

Environment

Personnel at risk

Etc.

CO2 laser

Nd:YAG laser


Laser Radiation RiskAssessment: Wavelength

1Near -IR

High

Noindication

Largehazardrange

(low MPE)

S

E

A

3UV

Low tomoderate

Noindication

Integratedexposure- scatter

plusbeam

2Visible

High

Visibleradiation

Largehazardrange

(low MPE)

4Mid/far-IR

Low tomoderate

Heatsensation

Smallhazardrange

Laser radiation

Output

Wavelength

Access to beam

Application

Environment

Personnel at risk

Etc.


Step-by-step

Risk Assessment

Identify potentially injurious situations(all operations, all hazards)

BenefitsInvolving users inidentifying hazardousactivities encouragesparticipation andownership of safety

RISKASSESS

Step 1


Step-by-step

Risk Assessment


Benefits

RISKASSESS

Step 1

Assess the risk for each situation(severity of injury, likelihood of exposure; then refer torisk tables)

Step 2

Involving users inidentifying hazardousactivities encouragesparticipation andownership of safety

Highlights the keyproblem areas


Step-by-step

Risk Assessment


Benefits

RISKASSESS

Step 1


Step 2

Review controls for each situations where the riskis intolerable(compare with current best practice and state whetheror not you consider existing controls to be satisfactory)

Step 3



Documents deviationsfrom Laboratory Code


Step-by-step

Risk Assessment


Benefits

RISKASSESS

Step 1


Step 2

Review controls for each situations where the riskis intolerable(compare with current best practice and state whetheror not you consider existing controls to be satisfactory)

Step 3

Review the new situation (repeat steps 2 and 3)Step 4

Review the riskassessmentperiodically



Documents deviationsfrom Laboratory Code


Tick list for open beams(Class 3B and 4)

Beam pathcontrol

Are:• All beam paths are enclosed as much as isreasonably practicable?

• All beam path components that generate errantbeams locally enclosed?

• All beam paths properly terminated?• All upwardly directed beams shielded to preventhuman exposure?

• All unprotected open horizontal laser beams lyingabove or below normal eye level?

• All lasers and optical components on the beam linesecurely mounted?

• Shiny surfaces (including jewellery) prohibitedaround laser beam paths?

• Laser sources and beam paths are kept under thecontrol of competent persons?


Tick list for open beams(Class 3B and 4)

Beam pathcontrol

Is:• Information of the current laser hazard clearlydisplayed at point of access to the laser area?

• Low level lighting used for ‘lights-out’ operation?• A safe method of beam alignment provided?• A visible or audible warning of the potential laserhazard provided?

• Laser safety eyewear provided?Are:• Persons at risk of exposure to the laser radiationadequately trained and instructed?

• Precautions in place to safeguard visitors enteringthe laser area?

• Unauthorised persons prevented from gainingaccess to the laser area?

• Multiple exposed wavelengths present?


Learning lessons fromaccidents

Laser accidents in French research laboratories

56% visible lasers

35% Nd:YAG (IR-A)

7% CO2

Of 55 accident reports in11 years, 27 resulted inpermanent eye injury

EU643 Report 'Clininal and epidemiologicalresearch'Commissariat Energie Atomique 1990

Accidentstatistics



Lessonslearned

Arrange for a fireassessment whereverClass 4 lasers are used

Carry a fire extinguisherand fit a smoke detector__________________

A Class 4 dye laser ignited the methanol solventused in the laser.

A small explosion and fire occurred in a laser dye(dioxane) mixture pump. Arcing in the pump motor,which ignited the flammable air/dioxane mixture,apparently caused the fire.

A Class 4 CO2 laser beam was reflected upwardsand ignited ceiling tiles in a laser laboratory. Theresearcher had left the room to examine samplesand returned a few minutes later when a smokedetector sounded.



Lessonslearned

A technician was replacing a flashlamp on a Nd:YAGlaser. The unit was electrically isolated, shut downand locked out. After 5 minutes wait for thecapacitor to discharge the worker touched thenegative terminal and was shocked. This wasidentified as a bleed circuit malfunction. No seriousharm.

A service engineer was electrocuted while installinga copper vapour laser. An interlocked protectivepanel had been manually bypassed during theinstallation to make adjustments. Despite CPR theserviceman expired.

Electrical hazards inlasers can be lethal

Proper HV training isessential

Provide earthing sticks

Consider secondaryscreening of internal HV__________________



Lessonslearned

An untrained summer research assistant wascarrying out alignment on his first day at work usinga 150 mW argon/dye laser. The laser was “slung” ina laser holder located under optical bench and thebeam was directed upwards through a beamchannel in the optical bench. The student chose tostand on top of the table and look downward whileattempting to align a turning mirror. No protectiveeyewear was used. The turning mirror slipped andthe beam was directed into his eye causing animmediate retinal burn on the edge of the macula.

During an experiment, a student climbed onto astool to adjust a periscope with a visible laser. Thestudent noticed a bright flash in her right eye. Noeyewear was worn ‘since she needed to observe thespot on a card’. No pain or bleeding, but anexamination the next day revealed a parafoveallesion.

Fully guard upward-travelling beams

Provide alignmentprocedures that facilitatethe use of protectiveeyewear

Provide proper training__________________



Lessonslearned

A student received a reflected Ti-Sapphire laserbeam from the plastic lid of a toolbox while he wasinstalling a laser beam safety tube. No eyeprotection was worn. The student had not receivedlaser safety training.

During optics alignment involving a 30 mJ pulsedNd:YAG laser (10 Hz) on a target using a prism, thebeam exceeded the prism’s critical angle and struckthe scientist in the eye resulting in a permanentretinal burn. No protective eyewear was worn.

A scientist bumped a mirror mount in a complexoptical array, causing a stray beam to move out ofthe horizontal plane. When leaning over the table, hewas struck in his left eye. An examination confirmeda macular lesion. No eyewear worn and safetyknowledge was limited.

Require the use of safetyeyewear wherever thereare exposed Class 3Band 4 laser beams

Control the use ofreflecting objects nearopen beam paths

Locally enclose prismsand other sources ofsecondary beams

Protect optics fromknocks__________________



Lessonslearned

A field service engineer was working on an argonlaser photocoagulator. During the inspection, theengineer was looking down the tube bore when thelaser spontaneously fired. He received an intrabeamocular exposure causing a permanent retinal lesion.

A Ti-sapphire accidentally discharged during beamalignment. The graduate student undertaking thealignment sustained a left eye injury. At 4 days, a300 µm hole and sub- retinal haemorrhage wasobserved.He suffers central vision loss and floaters.

A new frequency doubler didn't have A/R coatingsas requested. As the student left the room, beam hithim in the corner of his eye and caused inter-ocularbleeding. He still complains at 8 yrs of floaters andvision that looks "like looking through a dirtywindow".

Do not rely solely oncontrol circuits: add abeam stop or power down

Do not rely on coatingspecification for safety__________________



Lessonslearned

A technician received a 60 mW exposure from theBrewster window of an argon laser. Laser protectiveeyewear was available, but was not used theyapparently fogged easily and were annoying to use.A blind spot has persisted in the area of the lesion.

A frequency doubled Nd:YAG laser beam (532 nm)was Raman shifted to 770 nm in a methane cell. Thelaser protective eyewear provided protection at 532nm but did not protect for 770 nm and the techniciansuffered a retinal burn from a 0.8 µJ, 770 nm pulse.

During an alignment of a Nd:YAG laser, a productionworker looked through an opening in the top of achamber and his eyewear slid up as he leaned over.The beam reflection from a target paper went intohis eye causing a bright afterimage lasting 20minutes, which led to a permanent central retinalburn.

Nd:YAG reflectionfrom a surface coatedfilter. Safety gogglesmisted so he took themoff to get a better view ofthe display ….



Lessonslearned

A technician received a 60 mW exposure from theBrewster window of an argon laser. Laser protectiveeyewear was available, but was not used theyapparently fogged easily and were annoying to use.A blind spot has persisted in the area of the lesion.

A frequency doubled Nd:YAG laser beam (532 nm)was Raman shifted to 770 nm in a methane cell. Thelaser protective eyewear provided protection at 532nm but did not protect for 770 nm and the techniciansuffered a retinal burn from a 0.8 µJ, 770 nm pulse.

During an alignment of a Nd:YAG laser, a productionworker looked through an opening in the top of achamber and his eyewear slid up as he leaned over.The beam reflection from a target paper went intohis eye causing a bright afterimage lasting 20minutes, which led to a permanent central retinalburn.

Select eyewear that iscomfortable to wear,secure and does not fogup

Isolate wavelengths if theeyewear can’t provideadequate protection at all__________________


Module 2Laser safety assessment

Laser safety for safety supervisorsMike Green


Guarding

Standards forprotective equipmentLEGAL

Continuous inspection

How Long?

Regular inspection

Suggested times

Continuous operatorobservation

10 s

Short cycle operationwith intermittent

inspection100 s

Automated machineusage

30000 s


EN 12254 Screens for laser workingplaces - Safety requirements and testing

Standards forprotective equipment

Assessmentand testing

LEGAL

Applies up supervisedscreens to Maximumpower of 100 W and pulseenergy 30 J.

100 s testing for stability tolaser radiation

≥ 1 mm2 test area

Tests for mechanicalstrength and resistance toignition

Marking code (similar toeyewear)

Not a requirement:painted metal or

other non-flammableopaque materials can

be used


Use of PPEBESTPRACTICE


Hazard mitigation

Lasertype *

Laserwavelength

Filterscale number

ManufacturerID mark Mechanical

strength

EN207 marking code

D CWI 10-4 - 10-1

R 10-9 - 10-7

M < 10-9

Laser safetyeyewear


MaximumPermissibleExposure

that level of radiationto which,under normalcircumstances,persons may beexposed withoutsuffering adverseeffects.

MPEs andNOHDs

Definition

Maximum PermissibleExposure

The factors effecting the MPE are

Wavelength (must be within 180nm - 1mm)

Exposure duration (pluspulse width and PRF forpulsed lasers)


Exposure duration

MPEs andNOHDs

Direct cornealexposure


Values correspond to:• a single exposures ofthe eye

• a single wavelength

• a value averaged overa specific aperturediameter

0.1ps 1 ns 10s 3.104s

Wav

elen

gth

Mid

& F

ar

Visi

ble

&

UV

I

R

nea

r IR


Exposure duration

Wav

elen

gth

Laserpulses

Humanresponse

times

Prolongedexposure

<1ns to 0.1s 10s to 30,000s

Mid

& F

ar

Visi

ble

&

UV

I

R

nea

r IR

MPEs andNOHDs


Non

-line

ar e

ffect

s

retinal thermal

corneal thermal

corneal photochemical

Direct cornealexposure

Values correspond to:• a single exposures ofthe eye

• a single wavelength

• a value averaged overa specific aperturediameter


Exposure duration

Wav

elen

gth

Laserpulses

Humanresponse

times

Prolongedexposure

<1ns to 0.1s 10s to 30,000s

Mid

& F

ar

Visi

ble

&

UV

I

R

nea

r IR

MPEs andNOHDs


Non

-line

ar e

ffect

s

retinal thermal

corneal thermal

corneal photochemical

Limitingaperture

The diameter of the circleover which the MPE value

is to be averaged

Total power (or energy)through limiting aperturedivided by the area ofaperture


LASERHAZARD

Extendedsources


exposure duration

Mid

& F

ar

V

isib

le &

U

V

IR

ne

ar IR

Thermal retinal injury only

‘Small’ sources [α ≤ 1.5 mrad (αmin)]MPE applies

‘Medium’ sources [100 mrad ≥ α > αmin]MPE x α /αmin

‘Large’ sources [α > 100 mrad (αmax)]MPE x αmax/αmin (=66.7)

17 mm

αα



WavelengthGraph(s) of MPE vs. wavelength

MPE

(Wm

-2)

1000 Wm-2

10 Wm-2

3 Wm-2

Wavelength (nm)

10s exposure

400 700 1400180

Thermal corneal

Focusing + absorption depth effects

Photochemical activity



DurationGraph(s) of MPE vs. exposure duration

MPE

(Wm

-2)

time (s)

600 nm

10ps 1ns 18µs 10s

10 Wm-2

280 Wm-2

25 Wm-2 @ 0.25s

5 MWm-2

Equilibrium temperature

Diffusion limited temperature

Thermo-mechanical



DurationGraph(s) of MPE vs. exposure duration

MPE

(Wm

-2)

time (s)

600 nm

10ps 1ns 18µs 10s

5 mJm-2

0,15 mJm-2

MPE

(Jm

-2)

100 Jm-2

Equilibrium temperature

Diffusion limited temperature

Thermo-mechanical

Joule = Watt x time


Exposure durationMPE value range10-13 s

30,000 s

Exposure to single laser pulses

Duration of laser work


Exposure durationVisible Radiation

“light”

Aversion responseto bright light

≤ 0.25s

10-13 s

30,000 s


0.25 s Accidental viewingof visible laser radiation


Exposure durationSaccadic eye

movement10-13 s

30,000 s



10 s Accidental viewingof invisible laser radiation


Exposure durationBehaviouralmovement

10-13 s

30,000 s




100 s fixation on laserpoint source


Exposure durationUV radiation10-13 s

30,000 s




100 s fixation on laserpoint source

30,000 s intentional viewing ofextended sourceUV radiation.


Excimer (KrF) 0.25 1 10-8 30 Rhodamine Dye 0.55 1 10-7 5 10-3

Ruby (normal mode) 0.69 1 10-9 5 10-3

Ruby (Q-switched) 0.69 2 10-8 5 10-3

Nd:YAG (normal mode) 1.06 1 10-9 5 10-2

Nd:YAG (Q-Switched) 1.06 1 10-7 5 10-2

Carbon Dioxide 10.6 1 10-5 300

Typical Values of MPEsfor single pulse lasers

Laser Type λ Pulse MPE (µm) (s) (Jm-2)

MPEs andNOHDs

Single pulses

Exposure duration=

pulse duration



MPEs for intrabeam viewing of CW lasers

Laser Type λ MPE (Wm-2) (µm) 0.25s 100s 30000s

Helium 0.32 N/A 100 10-Cadmium 0.44 25 1.0 1.0

Argon Ion 0.49 25 6.3 6.30.51 25 10 10

He-Ne 0.63 25 10 10

Nd -YAG 1.06 N/A 50 50

CO2 10.6 N/A 1000 1000

MPEs andNOHDs

CW lasers

Choice of MPE depends onconditions of exposure.

Quoted values are for pointsources.



Assessed duration of exposure

MPEs andNOHDs

Multiple pulsesMPE is the smallest of:

Assessing multiple pulses

Condition 1Single pulse MPE for thelargest pulse


Assessed duration of exposure

AveragePower

MPEs andNOHDs

Multiple pulsesMPE is the smallest of:


Condition 2MPE for equivalent CW laser

Condition 1Single pulse MPE for thelargest pulse


MPEs andNOHDs

Multiple pulses

Condition 3 (excluding UV)Reduced single pulse(MPErsp)For a regular pulse train:MPErsp = MPEsp x N-1/4


Total-on-time-pulseTOTP

Sum of pulse energyand duration

MPE is the smallest of:

Condition 2MPE for equivalent CW laser(MPEcw)

Condition 1Single pulse MPE for thelargest pulse (MPEsp)

Summed over specified period (Generally 10s)

Assigned MPE is the smallest ofMPEsp, MPEcw, MPErsp


MPE values for repetitively pulsed lasersExcimer(0.25 µm, 10ns, 10 Hz)(0.25 µm, 10ns, 100 Hz)

Dye(0.55 µm, 100ns, 10 Hz)(0.55 µm, 100ns, 100 Hz)

Nd:YAG(1.06 µm, 100ns, 100 Hz)(1.06 µm, 100ns, 100 kHz)

CO2(10.6 µm, 10µm, 1 Hz)(10.6 µm, 10µm, 1 kHz)

Exp s3 104

0.25

3 104

10

MPE Jm-2

1 10-4

1 10-5

4 10-3

1.3 10-3

8.9 10-3

5.0 10-4

1701

MPEs andNOHDs

Repetitivelypulsed lasers

Average power MPE is thesmaller

Reduced single pulseMPE is the smaller



MPE

NOHD

MPEs andNOHDs

NOHD

NOHD Nominal Ocular Hazard Distance

is that distance at which the beamirradiance equals the appropriateocular MPE.

Calculation assumes:• conical expansion• simple power

distribution:



Class 1

ENOHD

MPEs andNOHDs

ENOHD Extended Nominal Ocular Hazard Distance

is that distance at which the beamirradiance equals the Class 1 AEL.


ENOHD

Calculation assumes:• conical expansion• simple power

distribution:


A laser beam has adiffuse edge

The beam diameter iscommonly defined as thatwhich encloses 86% of the

beam energy

Hazard distanceBASICS

Beam crosssection

Lase

r

radius

Powerdensity

100%

beam “diameter”

‘1/e2’ beam diameter

‘1/e’ beam diameter


High divergence/long range

Class 4CW visible

Higheyeandskin

injury

Fire

Mideye

injury

(>5xMPE)

Loweye

injury

(≤5xMPE)

Safeacci-

dentalif NO

viewingaids

(0.25s)

Safeacci-

dental

(0.25s)

No

risk

Question

Where does theNOHD and theENOHD lie in

this figure

Variation of hazardwith distance

icfo slides part 2

Documents

safety of laser productspart

workplacelaser safety

real orsuspected laser

employers responsible

administration of safetytr

shocklaser users

handall records

low level employer