Laser safety standards on the safe use of lasers ... - Sms4aviation.net

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Nov 15, 2013 (3 years and 8 months ago)

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Laser Safety

1

Course Curriculum for:

Laser Safety




I.

Course Prerequisites:




None

II.

Instructor's Qualifications:



Working knowledge of Laser Safety

III.

Course
V
isual
A
id and
H
andout
M
aterials:



Physical tour of laser to include all controls and safety devices

IV.

Training Method Used:






1.
0


Hours of classroom instruction




0.5


Hours of practical or hands on training

V.

Course Objectives:

Successful completion of this course is contingent upon the student's ability to demonstrate the
following:



Knowledge of Laser
Basics



Knowledge of the Laser Safety Program / Manual



Ability to identify Laser Beam Hazards



Understanding of the Biological and Associated Hazards



Understanding of the Regulations and Safety Standards



Ability to differentiate between the Laser Hazard Clas
sifications



Ability to choose the proper Personal Protective Equipment



Understanding of the Control Systems


VI.

Course Contents


The following sections describe various elements of laser safety.

A.

Laser Basics

This course will cover general laser safety with Site Specific Safety to be covered by your
supervisor.
Laser

is an acronym which stands for Light Amplification by Stimulated Emission of
Radiation
.

Lasers
are used in
applic
ations ranging from CD
-
Players,
microscopy, industrial welding
and bar
-
code scanners. Lasers
area rated based on their intensity and range from Class 1 to Class
4.
Each
facility

using Class 3b or 4 lasers will have a designated Laser Safety Officer.

1
.

Laser Safety Manual Topics Covered:



Definitions



Management Responsibilities



Employee Responsibilities



Control Measures



Laser Safety

2



Personal

Protective Equipment


2.

Laser Light Properties



Monochromatic:
L
ight consists of one color or wavelength as opposed to sun light
which has multiple wavelengths.



Directional: Beam is concentrated, tight and focused so it does not spread.


3.

Laser Types: Lasers can be described by:



W
hich part of the electromagnetic spectrum is represented:



Infrared



Visible Spectrum



Ultraviolet



T
he length of time the beam is
active:



Continuous Wave (Constant, steady
-
state delivery of laser power.)



Puls
ed

(Laser

which delivers energy in the form of a single or train of pulses.
Often achieved through the use of a “Q
-
Switch”, which functions as a shutter
that precisely controls t
he release of a single intense pulse.
)



Ultra
-
short Pulsed


4.

Laser Function

A.

The laser
optical cavity

contains the media to be excited with mirrors to redirect the
produced photons back along the same general path.

B.

The
pumping system

uses photons from another source such as a xenon gas flash
tube (optical pumping) to transfer energy to the media, electrical discharge within the
pure gas or gas mixture media (collision pumping), or relies upon the binding energy
released in chemical re
actions to raise the media to the metastable or lasing state.

C.

The

laser medium

can be a solid (state), gas, dye (in liquid), or semiconductor.
Lasers are commonly designated by the type of lasing material employed.

1.

Solid state

lasers have lasing material

distributed in a solid matrix, e.g., the
ruby or neodymium
-
YAG (yttrium aluminum garnet) lasers. The neodymium
-
YAG laser emits infrared light at 1.064 micrometers.

2.

Gas

lasers (helium and helium
-
neon, HeNe, are the most common gas
lasers) have a primary o
utput of a visible red light. CO2 lasers emit energy
in the far
-
infrared, 10.6 micrometers, and are used for cutting hard
materials.

3.

Excimer

lasers (the name is derived from the terms
excited

and
dimers
)
use reactive gases such as chlorine and fluorine mi
xed with inert gases
such as argon, krypton, or xenon. When electrically stimulated, a
pseudomolecule or dimer is produced and when lased, produces light in the
ultraviolet range.

4.

Dye lasers

use complex organic dyes like rhodamine 6G in liquid solution

or suspension as lasing media. They are tunable over a broad range of
wavelengths.

5.

Semiconductor

lasers, sometimes called diode lasers, are not solid
-
state
lasers. These electronic devices are generally very small and use low
power. They may be built int
o larger arrays, e.g., the writing source in some
laser printers or compact disk players.





Laser Safety

3













5.

Common Ultraviolet Lasers:




Common Ultraviolet Lasers

Argon
fluoride

Krypton
chloride

Krypton
fluoride

Xenon
chloride

Helium
cadmium

Nitrogen

Xenon
fluoride

193 nm

222 nm

248 nm

308 nm

325 nm

337 nm

351 nm



Ultraviolet (UV) radiation ranges from 200
-
400 nm.


10

-
12


10

-
10


10

-
8


10

-
6


10

-
4


10

-
2


10

0


10

2


10

4


10

6


10

8

x
-
rays

gamma rays

Ultra
-

violet

Infrared

Radar

Radio

waves

Electric

waves

Ionizin
g

Radiatio
n

Wavelength (cm)

Ultra
-

violet



Laser Safety

4

B.

Laser Beam Hazards


Biological
and Associated

1.

Biological Hazards


A.
Eye Injury
: Because of the high degree of beam collimation, a laser serves as an
almost ideal point source of intense light. A laser beam of sufficient power can
theoretically produce retinal intensities at magnitu
des that are greater than
conventional light sources, and even larger than those produced when directly
viewing the sun. Permanent blindness can be the result.
The most common types of
eye injuries sustained from lasers are:

o

Thermal damage

to the retina oc
curs in the Retinal Hazard Region (from 400
nm


1400 nm). Thermal damage is not cumulative, as long as the retina
cools down between exposures.


o

Photochemical damage

is severe at shorter visible wavelengths (violet &
blue) and is cumulative over a workin
g day.

o

Acoustic shock

from exposure to high energy pulsed lasers results in
physical tissue damage.

Laser energy is typically absorbed by the material
it strikes and increases the temperature of the
surface. When this occurs to biological tissues,
scaring or tissue damage can occur. Besides the
thermal effect caused by the increased
temperature, photoche
mical effects caused by
shorter wavelength laser emissions are possible.

Acute exposures can result in corneal or retinal
burns, possibly both

Chronic exposure can result in corneal or
lenticular opacities (Cataracts); or retinal injury.

Skin burns or carcinogenesis can result from
acute exposures of high levels of optical
radiation.

Retinal Hazard Region

o

The wavelength range of light that can enter the eye is 400 to 1400 nm,
though the range that we can actual
ly see is only 400


760 nm.

o

The eye can focus a collimated beam of light to a

spot 20 microns in diameter on the retina (called the
focal point
).

o

This focusing ability places the retina at risk when exposed to laser light
in the wavelength range that wi
ll penetrate to the retina, because even
fairly low wattage laser light can impact the retina with 100,000 times
the radiant power that entered the eye. Because of this optical gain,
laser light in the 400


1400 nm is referred to as the
Retinal Hazard
Re
gion
.

o

This is important to remember when working with infrared
lasers, because the retina can be injured even though the
laser is invisible.



Cornea
Lens
Vitreous
humor
Retina
Optic Nerve
Pupil
Sclera
Cornea
Lens
Vitreous
humor
Retina
Optic Nerve
Pupil
Sclera
(The graphic
from National Eye Institute)



Laser Safety

5

Cornea and Lens

o

Inflammation injury to the cornea is caused by ultraviolet (UV)
wavelengths (200
-
400 nm). This
is the same type of injury that is
caused by snow blindness.

o

Chronic exposure can cause cataract formation in the lens of the eye
just as UV from the sun does.









B.
T
hermal

I
njury
. The most common cause of laser
-
induced tissue damage is thermal
in
nature, where the tissue proteins are denatured due to the temperature rise
following absorption of laser energy.



Ultraviolet (UV)



UV can cause skin injuries comparable to sun burn.



As with damage from the sun, there is an increased risk for developing
skin
cancer from UV laser exposure.



Thermal Injuries



High powered (Class 4) lasers, especially from the infrared (IR) and visible
range of the spectrum, can burn the skin and even set clothes on fire.



2.

Non
-
Beam Hazards (hazards that are not associated

with the beam itself)




Electrical
:
Lethal electrical hazards from high power lasers.



Chemical
:
Eximer, dye and chemical lasers, and welding or cutting fumes



Non
-
Beam Optical
:
UV, Infra Red, or Visible Light



Compressed Gasses
:
Asphyxiation or explosion




Cryogenic:

coolant hazards




Noise



Fire and Explosion



Collateral Radiation: Radiation, other than laser radiation, associated with the
operation of a laser or laser system, e.g., radio frequency (RF) energy associated
with some plasma tubes, x
-
ray emission
associated with the high voltage power
supplies used with excimer lasers, shall be maintained below the applicable
protection guides.


C.

Laser Hazard Classes and Regulations

Laser safety standards on the safe use of lasers are processed and submitted for

approval
to the American National Standards Institute by the Laser Institute of America Accredited
Standards Committee Z136.
ANSI Standard (Z136.1)



American National Standards Institute (ANSI) approves the current laser safety
standards

Cornea
Lens


Laser Safety

6



Classifies Lasers
according to intensity and whether pulsed or continuous wave.



Requires each laser to have a label affixed near the beam outlet indicating the Class.



Class 1 and 2 are typically harmless, Class 3 and 4 are considered harmful.


The ANSI Laser Safety
standard
has defined

Laser Hazard
Classes
,
which are based on the
relative dangers associated with
using these lasers.




1.

Class 1 Lasers

This class cannot produce a hazardous beam because it is of extremely low power,

or

because it has been rendered
intrinsically safe

due to the laser having been
completely enclosed so that no hazardous radiation can escape and cause injury.


2.

Class 2 Lasers



These lasers are visible light (400
-
760 nm) continuous wave or pulsed lasers
which can emit energy greater th
an the limit for Class I lasers and radiation
power not above 1 mW.



This class is hazardous only if you stare directly into the beam for a long time,
which would be similar to staring directly at the sun.



Because class 2 lasers include only visible
wavelengths, the

aversion reaction

will usually

prevent us

from permanently damaging our eyes. The

aversion
reaction

refers to our tendency

to look away

from bright light.



3.

Class 3 Lasers


A.

Class 3a



This class of intermediate power lasers includes
any wavelength.



This class normally would not produce a hazard if viewed for only momentary
periods with the unaided eye.
Only hazardous for intrabeam viewing.



This class will not cause thermal skin burn or cause fires.


B. Class 3b



Visible and near
-
IR la
ser
s are very dangerous to the eye and can produce a
hazard if viewed directly.



Pulsed lasers may be included in this class.



This class will not cause thermal skin burn or cause fires.



Requires a Laser Safety Officer and written Standard Operating Procedur
es.


4.

Class 4 Lasers



These high
-
powered lasers are the most hazardous of all classes.



Even a diffuse reflection can cause injury.

Class 1
Class 2
Class 3a
Class 3b
Class 4
Most Hazardous
Least Hazardous
Class 1
Class 2
Class 3a
Class 3b
Class 4
Most Hazardous
Least Hazardous
Most Hazardous
Least Hazardous


Laser Safety

7



Visible and near
-
IR lasers will cause
severe

retinal injury and burn the skin.
Even diffuse reflections can cause retinal injuries.



UV and far
-
IR lasers of this class can cause injury to the surface of the eye and
the skin from the direct beam and specular reflections.



This class of laser can cause

fires.



Requires a Laser Safety Officer and written Standard Operating Procedures.



The focused beam of a laser can reflect and start fires. Reflection of a focused
beam can be extremely dangerous.



Lasers or laser systems can produce a hazard not only from
direct or
specular
reflections
, but also from a
diffuse reflection
. These, too, may produce fire and
skin hazards.


5.

Laser Safety Officer (LSO)



The
Laser Safety Officer (LSO)

is someone who has authority to monitor and
enforce the control of laser hazard
s and effect the knowledgeable evaluation and
control of laser hazards.



All Class 3b and 4 lasers must have a LSO.



The LSO will usually be a staff member who has primary authority for the laser in
question.

6
.

Maximum Permissible Exposure (MPE)



The
Maximum Permissible Exposure (MPE) is the highest level of radiation to
which a person can be exposed without hazardous effects.



The MPE is specified in W/cm
2

for continuous wave lasers and in J/cm
2

for
pulsed lasers. The value depends on wavelength, expo
sure duration and pulse
repetition frequency.



Exposure to radiation levels in excess of the MPE will result in adverse biological
effects, such as injury to the skin and/or eyes.




Laser Safety

8

7.

Warning Signs



Posted outside each entrance where laser is used (Class 3b

and Class 4)



Appropriate Signal Words required

































“Danger”: used for certain Class 3a, Class 3b or Class 4 lasers.

Class 3A (beam irradiance 2.5 mW/cm2),
Class 3B and Class 4 lasers:

Require the
ANSI DANGER sign format: white back
-
ground, red laser s
ymbol with black
outline and black lettering

Class 2 or Class 3A areas (if area
warning is deemed unnecessary by the
LSO): All signs (and labels) associated
with these lasers (when beam
irradiance for Class IIIA does not
exceed 2.5 mW/cm2) use the ANS
I
CAUTION format: yellow background,
black symbol and letters.

“Caution”: used for Class 2 and certain Class 3a lasers

䑵ain朠gim敳 ⁳敲eic攠end 桥r⁴im敳
睨敮 愠
temporary laser
-
controlled area

is
established, an ANSI NOTICE sign format
is required: white background, red laser
symbol with blue field and black lettering.
This sign is posted only during the time
when service is in progress.


Warning Sign (Example Notice)



Laser Safety

9

8.

Basic Safety Rules


A. Class 3



Never aim a laser at a person’s eye.



Using proper safety eyewear if there is a chance that the beam or a hazardous
specular reflection will the expose the eyes.



Permitting only experienced personnel to operate
the laser and not leaving an
operable laser unattended if there is a chance that the unauthorized user may
attempt to operate the laser.



A key switch should be used if untrained persons may gain access to the laser.
A warning light or buzzer may be used t
o indicate when the laser is operating.



Enclosing as much as the beam's path as practical.



Avoid placement of the unprotected eye along or near the beam axis as
attempted in some alignment procedures.

This is because the chance of
hazardous specular

reflections is greatest in this area.



Terminating the primary and secondary beams if possible at the end of their
useful paths.



Using beam shutters and laser output filters to reduce the beam power to less
hazardous levels when the full output power is no
t required.



Assuring that any spectators are not potentially exposed to hazardous conditions.



Attempting to keep laser beam paths above or below eye level for either sitting or
standing position.



Attempting to operate the laser only in a well
-
controlled ar
ea. For example,
within a closed room with covered or filtered windows and controlled access.



Labeling lasers with appropriate Class 3 danger statements and placarding
hazardous areas with danger signs if personnel can be exposed.



Mounting the laser on a
firm support to
ens
ure that the beam travels along the
intended path.



Ensuring

that individuals do not look directly into a laser beam with optical
instruments unless an adequate protective filter is present within the optical train.



Eliminating unnecessar
y specular (mirror
-
like) surfaces from the vicinity of the
laser beam path, or avoid aiming at such surfaces.



B. Class 4



Enclose the entire laser beam path if all possible. If done correctly, the laser’s
status could revert to a less hazardous classific
ation.



Confine open beam indoor laser operations to a light
-
tight room. Interlock
entrances to
en
sure that the laser cannot emit when the door is open, if the
Nominal Hazard Zone (NHZ extends to the entrances).



E
nsure that all personnel wear adequate eye
protection, and if the laser beam
irradiance represents a serious skin or fire hazard that a suitable shield is present
between the laser beam(s) and personnel.



Use remote firing and video monitoring or remote viewing through a laser safety
shield where fe
asible.



Laser Safety

10



Use beam shutter and laser output filters to reduce the laser beam irradiance to
less hazardous levels whenever the full beam power is not required.



Ens
ure that the laser device has a key
-
switch master control to permit only
authorized personnel to

operate the laser.



Install appropriate signs and labels as needed.



Use dark, absorbing, diffuse, fire resistant target and backstops where feasible.



Design safety into laser
-
welding and cutting equipment and laser devices used in
miniature work. If feasi
ble, such work should be accomplished in a light
-
tight or
baffled interlocked enclosure to eliminate the requirements for eye protection.



The focused beam of a laser can reflect and start fires. Reflection of a focused
beam can be extremely dangerous.



Lase
rs or laser systems can produce a hazard not only from direct or
specular
reflections
, but also from a
diffuse reflection
. These, too, may produce fire and
skin hazards.


D.

Control Measures


There are several measures that can be taken to prevent injury
from lasers. These measures
include:


1.

Engineering Controls

o

Engineering controls are measures that are incorporated into the laser system and
are designed to prevent injury to personnel. Engineered safety controls are
preferable to PPE or
Administrative controls.

o

Examples include



Protective housings



Interlocks on Removable protective housings



Service access panels



Key control master switch (Class 3b & 4)



Viewing Windows, Display Screens, Collecting Optics



Beam path enclosures



Remote interlo
ck connectors (Class 3b & 4)



Beam Stop or attenuator (Class 3b & 4)


2.

Administrative Controls

o

The most common administrative control is to restrict access to an area to only
essential people.




Laser Safety

11

3.

Personnel Protective Equipment

A. PPE for Skin



Ultraviolet lasers
and laser welding/cutting operations may require that tightly
woven fabrics be worn to protect arms and hands. Sun screen may also be used
to provide some additional protection.



For lasers with wavelengths > 1400 nm, large area exposure
s to the skin can
result in dryness and even heat stress.

B. PPE for Eyes



PPE is not
required for class 2 or 3a lasers unless intentional direct viewing >
0.25 seconds is
necessary.



Personnel Protective Equipment (PPE) for eyes exposed to Class 3b or 4
lasers
is mandatory. Eyewear with side protection is best. Consider these factors when
selecting eyewear:



Optical Density (OD) of the eyewear



Laser Power and/or pulse energy



Laser Wavelength(s)



Exposure time criteria

Maximum Permissible Exposure (MPE)



Filter characteristics, such as transient bleaching




Protect Your Eyes!


In a fraction of a second, your eyes can go
dark




4.


Warning Signs and Labels

See Section C, above


E.

Curriculum Summary:

Safety around lasers must be everyone’s primary concern.
To date, more than a dozen
electrocutions of individuals from laser
-
related accidents have been reported.
Another
example of laser hazards was

a

graduate student working with a CO2 laser was wiping
condensate from the laser tube when he received a 17 kV electrical shock. He suffered
cardiac arrest and 2
nd

degree burns.

In 1988, a laser repair technician was fatally electrocuted while working alone on a CO2
laser. He had reportedly defeated the inter
lock system.

Leading Causes of Laser Accidents



Unanticipated eye exposure during alignment



Available eye protection not used



Equipment malfunction



Laser Safety

12



Improper methods for handling high voltage

(This type of injury has resulted in
death.)



Inadequate training



Failure to follow SOP



Failure to provide non
-
beam hazard protection.



Equipment improperly restored following service



Incorrect eyewear selection and/or eyewear failure


L
aser Beam Hazards
: Eye injury and Thermal Injury are the primary beam hazards.

Non
-
Beam

Hazards
: Different Lasers systems come with different hazards such as chemical
exposures, electrical shock, optical (uv light ), collateral radiation (x
-
rays, RF), Noise,
Cryogenic, Compressed Gases, Fire and Explosion

Laser Hazard Classification
:

The higher number the hazard class the more dangerous the
laser. Class 1 is harmless, Class 4 lasers are the most dangerous.

PPE and Control Systems:
First choice is to enclose the beam path, if this is not possible
then protective eye
-
ware and clothing m
ust be utilized. Control systems must be set up to
protect everyone in the laser area.


F.

Curriculum Quiz:


A curriculum quiz score of 80% or greater is required to demonstration understanding of the
material presented. To ensure that the students understand the questions, this quiz may be
presented orally by the instructor.


Any student not trained to this l
evel must repeat the training and be retested.


























Laser Safety

13

Record of Training for:

Laser Safety




I.

Date of Training:

_______/______/______


II.

Method of Training:






䡯畲H ⁣l慳sr潯m⁩湳瑲畣瑩潮


††




䡯畲H ⁰牡 瑩c慬爠 慮摳 潮⁴牡i湩湧




III.

Course Contents:


A.

Laser Basics

1. Laser Safety Manual

2. Laser Light Properties

3. Laser Types

4. Laser Function

5. Common Ultraviolet Lasers

B. Laser
Beam Hazards

1. Biological Hazards

2. Associated Hazards

C. Laser Hazard Classes and
Regulations

1. Class 1 Lasers

2. Class 2 Lasers


3.Class 3 Lasers


4. Class 4 Lasers



5. Laser Safety Officer


6. Maximum Permissible Exposure


7. Warning Signs


8. Basic Safety Rules

D. Control Measures


1. Engineering Controls


2. Administrative Controls


3. Personnel Protective Equipment


4. Warning Signs and Labels

E.

Curriculum Summary

F. Curriculum Quiz



IV.

Visual Aids and
Handout Materials:

None applicable

V.

Student's Acknowledgment:

I hereby acknowledge that I have completed the training course outlined above and understand
the material presented to me.






















Employee’s Signature




Employee’s Name Printed


VI.

Instructor's Certification:

Through class participation and quiz completion, the above named student has successfully
demonstrated the knowledge and abilities as defined in the course objectives.



















Instructor’s Signature




Instructor’s Name Printed



Laser Safety

14

Curriculum Quiz for:

Laser Safety




Test Score:

____________________________

Passing Score: = 80%




This quiz is to be completed without the use of reference materials. Answer all questions by
circling the best choice.

If you do not understand a question, tell the instructor.


1.

True

False

If not properly protected, skin can be heated and burned by the light
energy from a laser.


2.

True

False

All classes of lasers are required to have a Laser Safety Officer
(LSO)


3.

True

False

Lasers or laser systems that are not hazardous under normal
operating conditions

are classified as Class 1.



4
.

Which of the following are
possible

causes of laser accidents?


a.

E
ye protection not
available or not
used

b.

Inadequate
operator
training


c.

Equipment malfunction

d.

All of the above



5
.

Which of the following classes of lasers is the most dangerous and would be found in metal cutting
or welding operations
:


a.

Class 1

b.

Class 2

c.

Class 3 (a and/or b)

d.

Class 4



6
.

Which
of these measures can be taken to prevent injury from lasers:


a.

Engineering Controls

(interlocked enclosures, barriers, etc.)

b.

Personnel Protective Equipment

(laser safe glasses)

c.

Warning signs and Labels

d.

All of the above



Laser Safety

15



7.

Which of the
following are ways that a laser can damage your eyes?


a.

Thermal damage

b.

Photochemical damage

c.

Acoustic shock

d.

Cataract formation

(from long term exposure)

e.

All of the above



8.

Who has the authority to monitor and enforce the control of laser hazards?


a.

Only y
our supervisor

b.

Only the
Laser Safety Officer (LSO)

c.

Any employee who is trained and passes this class.



9.

According to the
ANSI

Laser Safety Standard, which of the following
lasers must have signs posted
at the entrance to the area
?


a.

Class 1

b.

Class 2

c.

Class 3a

d.

Class 3b

and Class 4


10.

Looking

at a Class 4 laser or the indirect reflection of a Class 4 laser can cause permanent
blindness in less than…


a.

One minute

b.

30 seconds

c.

15 seconds

d.

One second