LASER SAFETY
REFRESHER TRAINING
LASER HAZARD CLASSES
Lasers are classified according to the level
of laser radiation that is accessible during
normal operation and maximum level of
exposure possible.
Lasers may be classified under:
• The Federal Laser Production Performance
Standard (CDRH standard)
• The American National Standard for Safe Use
of Lasers
• IEC 60825 International Standard
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LASER CLASSIFICATION SUMMARY
ANSI Z136.1-2007
Class 1
Incapable of causing injury during normal operation
Class 1M
Incapable of causing injury during normal operation
unless collecting optics are used
Class 2
Visible lasers incapable of causing injury in 0.25 s.
Class 2M
Visible lasers incapable of causing injury in 0.25 s
unless collecting optics are used
Class 3R
Marginally unsafe for intrabeam viewing; up to 5 times the
class 2 limit for visible lasers or 5 times the class 1 limit
for invisible lasers
Class 3B
Eye hazard for intrabeam viewing, usually not an eye
hazard for diffuse viewing
Class 4
Eye and skin hazard for both direct and scattered exposure
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LASER SAFETY STANDARDS

The Federal Laser Product Performance Standard (FLPPS)
of the Center for Devices and Radiological Health (CDRH)
This is federal law that applies to US manufacturers of lasers.

The American National Standard for Safe Use of Lasers (ANSI Z136.1)
This is a “best approach” VOLUNTARY Standard applying to the use
of lasers, which is “recognized by” :
The Occupational Safety and Health Administration (OSHA)

IEC 60825 International Standard
Lasers classified and labeled in accordance with this standard may
be sold in the US. CDRH & ANSI Z136.1 do not agree with all the
provisions of this standard.
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FEDERAL SAFETY REQUIREMENTS FOR CLASS 1 LASER
SYSTEMS WITH ENCLOSED CLASS 3b AND 4 LASERS
Protective Housing
prevents access to laser radiation above safe level.
Safety Interlocks
terminate laser beam if protective housing is opened.
Only authorized personnel may operate laser with interlocks defeated.
Warning Labels
alert personnel if opening the housing might expose a laser hazard.
Viewing Windows and Optics
limit laser and collateral radiation to safe levels.
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CDRH CLASS WARNING LABELS
Laser Radiation
Do Not Stare Into Beam
Helium Neon Laser
1 milliwatt max/cw
CLASS II LASER PRODUCT
Class 2
Class 3R with expanded beam
VISIBLE LASER RADIATIONAVOID EYE OR SKIN EXPOSURE TO
DIRECT OR SCATTERED RADIATION
Argon Ion
Wavelength: 488/514 nm
Output Power 5 W
CLASS IV Laser Product
Class 3R with small beam
Class 3B
Class 4
The Laser Safety Officer must evaluate all lasers and labeling for safety
compliance with ANSI Z136.1 recommendations.
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INTERNATIONAL LASER
WARNING LABELS
INVISIBLE LASER RADIATION
AVOID EYE OR SKIN EXPOSURE
TO DIRECT OR SCATTERED RADIATION
CLASS 4 LASER PRODUCT
WAVELENGTH
MAX LASER POWER
EN60825-1
Symbol and Border: Black
Background: Yellow
10,600 nm
200 W
1998
Legend and Border: Black
Background: Yellow
The Laser Safety Officer must evaluate all lasers and labeling for safety
compliance with ANSI Z136.1 recommendations.
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LASER SPECTRUM
UV -- potential photochemical
damage (eyes and skin)
avoid long term hazardous
exposures at low levels
VISIBLE LIGHT -- 400 -700 nm
seeing light helps avoid
hazardous exposures
NEAR IR (NIR) -- 700-1400 nm
Is poorly or cannot be seen, but the eye does focus these wavelengths on the retina, producing an invisible
retinal hazard and the potential for serious eye injury. The most stringent laser safety precautions are
required in this wavelength range, which contains several of the most useful lasers.
FAR IR -- COMPLETELY ABSORBED BY WATER BEFORE (REACHING) RETINA
Can damage other parts of the eye, but absorption spread over a larger area, allowing larger exposures
CHARACTERISTICS OF LASERS AND
THEIR EFFECTS ON LASER HAZARDS
Spectral characteristic – Wavelength
In general, shorter wavelengths are more hazardous in any spectral
region, but Near Infrared lasers are the most hazardous because they
are invisible retinal hazards.
Temporal characteristic – Pulse Duration
In general, pulsed lasers are more hazardous than CW lasers.
The shorter the pulse duration, the higher the peak power and the
greater the hazard.
Spatial characteristic – Beam Divergence
Low beam divergence results in a large intra-beam hazard distance.
Focusing characteristic
High retinal irradiance of focused beam creates extreme retinal hazard
for visible and near infrared lasers.
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EYE INJURY BY Q-SWITCHED LASER
Retinal (macular region) injury produced by four pulses from a Nd:YAG laser.
Pulse duration ~20 ns
Pulse energy ~15 mJ – 7500x the safe level (maximum permissible exposure – MPE)
Each pulse -- tiny explosion/shockwave -- severe damage
3 weeks later -- permanent destruction of
the macular region. Visual acuity ~20/400
and will not improve.
Short pulse lasers produce the
greatest eye hazards.
This injury could not have occurred
if the individual had been wearing
the appropriate laser safety
eyewear.
Photo courtesy of U S Army Center for Health Promotion and Preventive Medicine
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CAUSES OF LASER ACCIDENTS
Studies of laser accidents have shown that there are usually
several contributing factors. The following are common
causes of laser injuries:
• Inadequate training of laser personnel
• Alignment performed without adequate procedures
• Failure to block beams or stray reflections
• Failure to wear eye protection in hazardous situations
• Failure to follow approved standard operating
procedures or safe work practices
Don’t risk yours or another’s safety – WORK SAFE
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OVERVIEW OF ANSI Z136.1
The ANSI Standard is a guideline for decision making. Laser users trained in accordance with the standard are
expected to take individual responsibility for the safe use of all lasers. The OSHA Technical Manual, Section III,
Chapter 6, LASER HAZARDS is available at http://www.osha.gov/dts/osta/otm/otm_iii/otm_iii_6.html
This document can serve as an effective reference for laser safety programs. It is not necessary to have a copy of the ANSI
Standard or be an expert in the details of that standard to maintain an effective laser safety program.
1. MANAGEMENT APPOINTS LASER SAFETY OFFICER
2. LSO VERIFIES LASER CLASSIFICATION
3. LSO EVALUATES HAZARDS BY DETERMINING
MPE -- OD -- NHZ
4. LSO SPECIFIES CONTROL MEASURES
ENGINEERING CONTROLS
ENCLOSURES
INTERLOCKS
WARNING SYSTEMS
ADMINISTRATIVE AND PROCEDURAL CONTROLS
AUTHORIZED PERSONNEL
SOP (INCLUDING ALIGNMENT)
TRAINING
PROTECTIVE EQUIPMENT
EYEWEAR
BARRIERS
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Laser Hazard Evaluation REQUIREMENT
PRIOR TO USE
each Class 3b or 4 laser/laser system must be evaluated for the
following hazards by the LSO
1. Calculation of:
Maximum Permissible Exposure
Optical Density of Eyewear
Nominal Hazard Zone -- Each of these is explained in the following slides.
2. Evaluation of laser use environment (hazards)
Required controls
3. Operator evaluation
Training
Level of responsibility assumed by AU
The personnel who may be exposed to laser radiation
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Maximum Permissible Exposure (MPE)
The level of laser light to which a person may be exposed
without risk of injury.
primary factors effecting MPE:

exposure type (Intrabeam eye exposure -- worst case)

wavelength

pulse characteristics

exposure duration
0.25 s -- visible laser
10 s -- invisible laser
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OPTICAL DENSITY OF
LASER SAFETY EYEWEAR
E0
Laser
MPE
Eyewear
Optical Density – logarithmic
expression of filter attenuation
Or
OD
0
1
2
3
4
5
6
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% Transmission
100%
10%
1%
0.1%
0.01%
0.001%
0.0001%
OD = log
E0
MPE
worst case OD (based on the assumption that the entire beam
enters the eye)
beam diameter, smaller than pupil -- the hazard does not increase
worst situation -- largest beam possible enters eye (produces
smallest spot on the retina)
The laser safety officer will assist in
determining appropriate optical densities for
each wavelength of class 3B & 4 lasers.
NOMINAL HAZARD ZONE
The space within which the potential exposure exceeds the MPE, or distance required for
divergence to decrease irradiance below MPE. This is often a large distance, consequently safe
use requires termination on a diffuse reflecting beam block.
Intrabeam
Nominal Hazard Zone
Diffuse Reflection
Nominal Hazard Zone
The diffuse reflection NHZ is the distance that scattered irradiance levels exceed MPE. A
diffuse reflection is an omnidirectional hazard.
The LSO determines NHZ exposure condition (intrabeam, diffuse reflection, focusing
lenses, optical fibers, etc.)
HAZARD EVALUATION
BY LASER USERS
All users of lasers with exposed beams should:

Understand the hazards associated with the
laser they use

Evaluate the control of hazards every time they
operate the lasers

Use their best judgment in controlling all laser
hazards (be conservative; don’t take chances)

Consult their Laser Safety Officer whenever they
have safety concerns or questions
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LASER CONTROL MEASURES
ANSI Section 4.1
“Control Measures shall be devised to reduce the possibility of exposure
of the eye and skin to hazardous levels of laser radiation.”
Types of Control Measures
• Engineering -- built into equipment or facility (AUTOMATIC PROTECTION)
• Administrative -- POLICIES (i.e., only authorized personnel may operate lasers)
• Procedural – working procedures (STANDARD OPERATING PROCEDURE)
LSO determines CONTROL MEASURES to reduce possible laser
EXPOSURES < MPE for all CLASS 3B/4
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BEAM PATH ENCLOSURES
Section 4.3.6
FULLY ENCLOSED BEAM PATH
Class 1
System
Laser
LIMITED OPEN BEAM PATH
Laser
Some scattered light
escapes. NHZ is small.
FULLY OPEN BEAM PATH
Larger NHZ requires laser
controlled area.
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Laser
OPEN BEAM CONTROL MEASURES
Section 4.3.1.1
Laser Controlled Area -- Class 3B Or 4 Lasers with exposed beams
 access to the area is controlled
 laser hazards are controlled -- engineering & procedural controls specified in SOP
 some individual is in control of the laser hazards.
 LASER WARNING SIGN must always be posted at the entryway to a CLASS 4 laser controlled
area
Eye Protection
 Laser safety eyewear must be used inside the controlled area as specified in the SOP.
Beam Control
 Barriers, shrouds, and beam stops are used to limit the NHZ inside the controlled area.
Administrative and Procedural Controls
 Administrative and procedural controls define approved personnel and procedures. Written
Standard Operating Procedures (SOPs) are required for class 4 lasers
Education and Training
 Only trained personnel are allowed inside the laser controlled area
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CLASS 4 ENTRYWAY CONTROLS
Section 4.3.10.2.2
ENTRYWAY CONTROLS ARE REQUIRED FOR CLASS 4 LASER CONTROLLED AREAS.
1. Non-Defeatable Entryway Controls -- terminates laser beam with opened door
 Doorway interlock is non-defeatable
 Training of authorized users only
2. Defeatable Entryway Controls -- may be bypassed allowing entrance/exit controlled area
without laser operation interruption
 Doorway interlock is defeatable during “non-hazardous operation “
 Requires training of all personnel with access
 Requires barrier and eyewear at door
3. Procedural Entryway Controls – only when hazards are well controlled and if all personnel
with access are trained in laser safety.
 No doorway interlock
 Training of all personnel with access
 Barrier and eyewear at door
 Visible or audible signal at doorway
LABORATORY DOORS may be LOCKED during laser operation, but there must
be provisions for EASY EMERGENCY INGRESS AND EGRESS.
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LASER PROTECTIVE BARRIERS
LASER PROTECTIVE BARRIERS/CURTAINS -- limits NHZ inside laser controlled areas

barriers also used to protect entryways, computer work stations, and workbenches

NO direct optical path may exist between laser optics tables and computer stations in laser
laboratories.
Photos courtesy of
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CURBS ON OPTICAL TABLE
Beam control is improved by using curbs on optical table, especially when all beams are horizontal.
Curbs on the optical table block any reflections and confine the hazard to the area of the optical table.
These curbs may be removed easily to provide greater access for reconfiguration or alignment.
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BEAM CONTROL METHODS
LIMITING the NHZ inside a laser controlled area greatly enhances safety in a laser laboratory.
use beam blocks, beam tubes, partial enclosures, and curbs on optical tables
In many cases the NHZ can be confined to the optical table.
IT’S NOT NECESSARY to interlock all enclosures inside laser laboratories
appropriate labels should always be applied to alert workers to potential laser hazards
LASER SAFETY EYEWEAR
Laser safety eyewear is available in
glass or plastic for all laser
wavelengths.
The required Optical Density of the
eyewear is determined in the hazard
analysis performed by the LSO.
 EYEWEAR SHOULD NEVER BE VIEWED AS THE FIRST CONTROL MEASURE TO BE APPLIED.
• In all cases ENGINEERING AND PROCEDURAL CONTROLS should be devised to reduce and limit
the possible exposure to hazardous laser light.
• eyewear should then be required as a LAST LINE OF DEFENSE in case everything else fails.
• Most laser Eye Injuries have occurred when Other Controls Proved Inadequate and the worker was
Not Wearing Eyewear.
 EYEWEAR WOULD HAVE PREVENTED MOST LASER EYE INJURIES, BUT IT DOES NOT MAKE
THE WEARER INVULNERABLE.
It is never safe to stare into a laser beam, even if wearing laser protective eyewear.
 THE GREATEST RISK OF EYE INJURY OCCURS WHEN NEAR IR LASERS ARE OPERATED
WITH THE BEAM EXPOSED.
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EYEWEAR LABELS
Optical Density curves for all eyewear are available from the manufacturers.
IN RESEARCH SITUATIONS it is sometimes necessary to use eyewear that is NOT LABELED FOR
THE SPECIFIC WAVELENGTHS IN USE.
IN THESE CASES, EYEWEAR DATA MUST BE AVAILABLE IN THE LABORATORY.
All eyewear must be labeled with wavelength and optical density.
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WHO HAS PRIMARY RESPONSIBLITY FOR LASER
SAFETY ANY TIME A CLASS 3B OR CLASS 4 LASER IS
OPERATED?
The person operating the laser always has the primary
responsibility for all hazards associated with laser use.
If YOU create laser photons, YOU ARE RESPONSIBLE for the safety of anyone who might be
exposed to those photons.
1st RESPONSIBILITY OF LASER USERS -- ASSURE THE SAFETY OF OTHERS
2nd -- protect Yourself
SECTION 1.3.3 OF THE ANSI STANDARD STATES: “Employees who
work with lasers or laser systems and their supervisors have responsibilities
for establishing the safe use.”
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SUGGESTED SOP FORMAT
ANSI Standard - Must be written, available at the laser, and include alignment methods –
REQUIRES LSO APPROVAL (CLASS 3B/CLASS 4 LASERS)
1. Introduction – Description of laser
Type and wavelength; Intended application & Location
Average power or energy per pulse
Pulse duration and repetition rate for pulsed lasers
2. Hazards – List all hazards associated with laser
Eye and skin hazards from direct and diffuse exposures
Electrical hazards
Laser generated air contaminants
Other recognized hazards
3. Control Measures – List control measures for each hazard
Include the following:
Eyewear requirement, include wavelength and OD
Description of controlled area and entry controls
Reference to equipment manual
Alignment procedures (or guidelines)
4. Authorized Personnel
5. Emergency Procedures
SAFE BEAM ALIGNMENT
•
Most beam injuries occur during alignment.
•
Only trained personnel may align class 3B or class 4 lasers (NO
EXCEPTIONS!)
•
Laser safety eyewear is required for class 3B and class 4 beam alignment.
•
ANSI REQUIRES approved, written alignment procedures for ALL class 4
laser alignment activities and recommends them for class 3B.
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ALIGNMENT GUIDELINES FOR
CLASS 3b AND 4 LASERS
1.
Exclude unnecessary personnel from the laser area during alignment.
2.
Where possible, use low-power visible lasers for path simulation of high power visible or invisible lasers.
3.
Wear protective eyewear during alignment. Use special alignment eyewear when circumstances permit
their use.
4.
When aligning invisible beams, use beam display devices such as image converter viewers or phosphor
cards to locate beams.
5.
Perform alignment tasks using high-power lasers at the lowest possible power level.
6.
Use a shutter or beam block to block high-power beams at their source except when actually needed
during the alignment process.
7.
Use a laser rated beam block to terminate high-power beams downstream of the optics being aligned.
8.
Use beam blocks and/or laser protective barriers in conditions where alignment beams could stray into
areas with uninvolved personnel.
9.
Place beam blocks behind optics to terminate beams that might miss mirrors during alignment.
10.
Locate and block all stray reflections before proceeding to the next optical component or section.
11.
Be sure all beams and reflections are properly terminated before high-power operation.
12.
Post appropriate area warning signs during alignment procedures where lasers are normally class 1.
13.
Alignments should be done only by those who have received laser safety training.
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SAFE WORK PRACTICES
 Never intentionally look directly into a laser. Do not stare at the light from
any laser. Allow yourself to blink if the light is too bright.
 Do not view a Class 3a (or any higher power) laser with optical instruments.
 Never direct the beam toward other people.
 Operate lasers only in the area designed for their use and be certain that the
beam is terminated at the end of its use path. Never allow a laser beam to
escape its designated area of use.
 Position the laser so that it is well above or below eye level.
 Always block the beam with a diffuse reflecting beam block.
 Remove all unnecessary reflective objects from the area near the beam’s
path. This may include items of jewelry and tools.
 Do not enter a designated Class 3b or Class 4 laser area (posted with a
DANGER sign) without approval from a qualified laser operator. Eye
protection is required in these areas.
 Always wear laser safety eyewear if a class 4 invisible beam is exposed.
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