NSEC Nanoscale Science and Engineering Center MRSEC

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NSEC Nanoscale Science and Engineering Center
MRSEC Materials Research Science and Engineering
Center
Laser Safety Irving P. Herman October 15, 2004
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Overview

• Types of hazards with lasers, causes, avoidance
• Case studies, IPH and other
• Observations and Closing Remarks

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Types of hazards include 1. Eye Acute
exposure of the eye to lasers of certain
wavelengths and power can cause corneal or
retinal burns (or both). Chronic exposure to
excessive levels may cause corneal or lenticular
opacities (cataracts) or retinal injury. 2. Skin
Acute exposure to high levels of optical
radiation may cause skin burns while
carcinogenesis may occur for ultraviolet
wavelengths (290-320 nm). 3. Chemical Some
lasers require hazardous or toxic substances to
operate (i.e., chemical dye, excimer lasers). 4.
Electric shock Most lasers produce high
voltages that can be lethal. 5. Fire hazards
The solvents used in dye lasers are flammable.
High voltage pulse or flash lamps may cause
ignition. Flammable materials may be ignited by
direct beams or specular reflections from high
power continuous wave (CW) infrared lasers.
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The majority of injuries involve the eye and, to
a lesser extent, the skin
Summary of reported laser accidents in the United
States and their causes from 1964 to 1992
http//www.adm.uwaterloo.ca/infohs/lasermanual/doc
uments/section11.html
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The majority of injuries occur during alignment
procedures, or because the protective eyewear was
either inappropriate or not used
Summary of reported laser accidents in the United
States and their causes from 1964 to 1992
http//www.adm.uwaterloo.ca/infohs/lasermanual/doc
uments/section11.html
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Eye Damage Laser Classifications
1. Class 1 Low-power lasers and laser systems
that cannot emit radiation levels greater than
the Maximum Permissible Exposure (MPE). Class 1
lasers and laser systems are incapable of causing
eye damage and are therefore exempt from any
control measures.2. Class 2 Visible, low power
lasers or laser systems that are incapable of
causing eye damage unless they are viewed
directly for an extended period (greater than
1000 seconds).3. Class 3 Medium-power lasers
and laser systems capable of causing eye damage
with short-duration (lt0.25 s) exposures to the
direct or specularly reflected beam. Includes
Class 3a and 3b lasers.4. Class 3a Lasers or
lasers systems that normally would not produce a
hazard if viewed for only momentary periods with
the unaided eye. They may present a hazard if
viewed using collecting optics.5. Class 3b
Lasers or lasers systems that can produce a
hazard if viewed directly. This includes
intrabeam viewing of specular reflections.6.
Class 4 High power lasers and laser systems
capable of causing severe eye damage with
short-duration (lt0.25 s) exposures to the direct,
specularly reflected, or diffusely reflected
beam. Class 4 lasers and laser systems are also
capable of causing severe skin damage and
igniting flammable and combustible materials.
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Eye Damage Laser Classifications
Class 1 Lasers
Class 2 Lasers (Power lt 1 mW, commonly found in
alignment applications)
Class 2a Lasers (special purpose, Power lt 1 mW,
e.g. barcode readers)
Class 3a Lasers (Power 1-5 mW) (Typical laser
pointer)
Class 3b Lasers (CW Power 5-500 mW or less
than 10 J/cm2 for a ¼-s pulsed system)
High power pointers He-Ne laser
Class 4 Lasers (CW Power gt 500 mW or greater
than 10 J/cm2 for a ¼-s pulsed system)
Many of our lasers are Class 4
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Eye Damage Laser Classifications, Class 4
Argon-ion, krypton ion lasers dye lasers, Ti
sapphire lasers
Excimer lasers dye lasers
5 kW CO2 laser (most pulsed, cw)
50 watt NdYAG laser (1064nm) (most pulsed, cw,
also some diode pumped)
Copper-Vapor laser
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Potential Eye Damage
The biological damage caused by lasers is
produced through thermal, acoustical and
photochemical processes. Thermal effects are
caused by a rise in temperature following
absorption of laser energy. The severity of the
damage is dependent upon several factors,
including exposure duration, wavelength of the
beam, energy of the beam, and the area and type
of tissue exposed to the beam. Normal focusing
by the eye results in an irradiance amplification
of roughly 100,000 therefore, a 1 mW/cm2 beam
entering the eye will result in a 100 W/cm2
exposure at the retina. The most likely effect of
intercepting a laser beam with the eye is a
thermal burn which destroys the retinal tissue.
Since retinal tissue does not regenerate, the
damage is permanent.
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Eye Damage Laser Heating
CW lasers DT (1-R)P/2p1/2Kw P is the power K
is the thermal conductivity w is the spot
size Pulsed lasers Little thermal diffusion
during pulse DT (1-R)Fpulse/rC Much thermal
diffusion during pulse DT (1-R)Fpulse/rC(2Dtpul
se)1/2 (1-R)Ipulse(tpulse)1/2/rC(2D)1/2
Fpulse is the pulse fluence, Fpulse Ipulse
tpulse Ipulse is the pulse intensity tpulse is
the laser pulse width C is the heat capacity D is
the thermal diffusivity K/rC
High laser powers. The eye can focus them to
small spots.
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Potential Eye Damage
Acoustical effects result when laser pulses with
a duration less than 10 microseconds induce a
shock wave in the retinal tissue which causes a
rupture of the tissue. This damage is permanent,
as with a retinal burn. Acoustic damage is
actually more destructive than a thermal burn.
Acoustic damage usually affects a greater area of
the retina, and the threshold energy for this
effect is substantially lower. Beam exposure may
also cause Photochemical effects when photons
interact with tissue cells. A change in cell
chemistry may result in damage or change to
tissue. Photochemical effects depend strongly on
wavelength. N.B. the severity of the eye damage
depends strongly on whether it occurs by
intrabeam exposure or scattered laser light
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www.yorku.ca
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Eye Damage Focusing Remember Your Eyes Are
Designed to Focus
dfocus 2.44 l(flens/Dbeam,lens)
If the irradiance entering the eye is 1 mW/cm2,
then the irradiance at the retina will be 100
W/cm2.
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Eye Damage Different Wavelengths
Ultraviolet Excimer lasers XeCl, 308 nm KrF,
248 nm ArF, 193 nm He-Cd laser 325
nm Visible Argon-ion laser 488 nm, 514 nm (also
krypton-ion) He-Ne laser 632.8
nm Frequency-doubled YAG 532 nm Dye laser
Tunable in visible Diode lasers Infrared Ti-sapph
ire 680-1100 nm Diode lasers Nd3/YAG etc.
lasers 1.06 mm CO2 laser 10.6 mm
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Eye Damage Different Wavelengths
Eye transmission
http//www-training.llnl.gov/wbt/hc/LaserRefresh/E
yeTransmission.html
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(No Transcript)
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Exposure Limits Retinal Injury Thresholds - I
- At 10-12 seconds the threshold for a retinal
injury is 10-7 J/cm2 (i.e. 105 W/cm2). -
Because of the x 105 enhancement in the eye this
value is elevated to 10-2 J/cm2 (i.e. 1010
W/cm2) on the retina. - These exposure levels are
further enhanced by self-focusing.
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Exposure Limits Retinal Injury Thresholds - II
Numerical example A 4 reflection from a 2.5 mJ
laser in a 2 mm beam, gives an exposure of
(10-4 J)/(0.78 x (0.2)2 cm2) 3.2 x 10-3 J
/cm2 , exceeding the threshold value on the
cornea of 10-7 J/cm2 by a factor 3.2 x 104.
To be adequately protected against this exposure,
protection with an optical density (OD) of
log(3.2 x 104) 4.5 is required
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Example of Eye Damage
Experience has demonstrated that most laser
injuries go unreported for 2448 hours by the
injured person. This is a critical time for
treatment of the injury.
http//www.adtdl.army.mil/cgi-bin/atdl.dll/fm/8-50
/INTRO.htm
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Eye Damage Focusing Remember Your Eyes Are
Designed to Focus
With safety rule
Cornea Damage BAD
Retina Damage WORSE
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Eye Damage Lasers are used for eye surgery, so
what do you expect?
Argon-ion laser -VIS- diabetes vascular control
Near IR
Lasik surgeryUV/excimer laser
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• Beam Control To minimize direct eye exposure,
  observe these precautions
• Do not intentionally look directly into the laser
  beam or at a specular reflection, regardless of
  its power.
• Terminate the beam at the end of its useful path.
• Locate the beam path at a point other than eye
  level when standing or when sitting at a desk.
• Orient the laser so that the beam is not directed
  toward entry doors or aisles.
• Minimize specular reflections.
• Securely mount the laser system and all optics on
  a stable platform to maintain the beam in a fixed
  position during operation and limit beam traverse
  during adjustments.
• Confine primary beams and dangerous reflections
  to the optical table.
• Clearly identify beam paths and ensure that they
  do not cross populated areas or traffic paths.
• 9. When the beam path is not totally enclosed,
  locate the laser system so that the beam will be
  outside the normal eye-level range, which is
  between 1.2 to 2 meters from the floor. A beam
  path that exits from a controlled area must be
  enclosed wherever the beam irradiance exceeds the
  MPE.

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Additional Controls for Class 1 and Class 2
Lasers Warning signs Post at each entrance to
the operating area "CAUTION - LOW POWER LASER"
signs. If the laser has not been labeled by the
manufacturer, attach a label on the laser with
its classification and relevant warning
information.
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• Additional Controls for Class 3 and 4 Lasers
• Standard operating procedures (SOP) post them.
• 2. Labels A laser classification label must be
  conspicuously affixed to the laser.
• 3. Warning Signs Each entrance must be posted
  with a danger sign.
• Warnings Devices Entrances to labs.
• Safety Interlocks Alarms? Voice Warnings?
• 6. Limited entry to the rooms with lasers.
• Permanently attached beam stop or attenuator and
  emission delays.
• Class 3b and 4 laser with l gt 710 nm must be
  terminated with fire resistant material.
• Securely fasten all mirrors, prisms, beam stops,
  etc. in the beam path. Ensure that the laser is
  also securely fastened.
• Circuit breakers must be identified for each
  laser.

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• Additional Controls for Class 3 and 4 Lasers,
  continued
• Beam Enclosure The entire beam path of Class 3
  and Class 4 lasers, including the target area,
  should be surrounded by an enclosure equipped
  with interlocks that prevents operation of the
  laser system unless the enclosure is properly
  secured. When total enclosure of the laser beam
  path is not practical, both the non-enclosed
  laser beam and any strong reflections must be
  terminated at the end of their useful path using
  such devices as backstops, shields or beam traps.
• Minimize diffuse and specular reflections
  enclose or shield beam paths.
• Ultraviolet (UV) and infrared (IR) lasers
  require additional controls.
• No direct viewing (primary and specular
  reflections of Class 3/4 are particularly
  hazardous).
• Never remove a beam block unless you know the
  beam will be safe!!!
• Align beams at low power!!!
• Do not leave lasers unattended.
• Laser protective eye wear should be worn
  whenever MPE levels may be exceeded, unless beams
  are totally enclosed.
• Protection for the skin may be afforded through
  the use of clothing to cover normally exposed
  skin areas.

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High Voltage Dangers Laser Power Supplies
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High Voltage Dangers Laser Power Supplies
Effect DC (mA) AC (60 Hz,
mA) Slight sensation at contact
point 0.6 0.3 Perception threshold 3.5 0.7
Shock - not painful, no loss of muscular
control 6 1.2 Shock - painful, no loss of
muscular control 41 6 Shock - painful, let-go
threshold 51 10.5 Shock - painful, severe
effects 60 15 muscular contractions,
breathing difficulty Shock - possible ventricular
fibrillation 500 100 (loss of normal heart
rhythm) Heart paralysis and severe burns gt 4
A Effect of currents on the human body (for
about 1 sec). (all values are approximate)
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High Voltage Dangers
Resistance through dry skin is roughly 100,000 to
600,000 ohms Resistance through dry skin it is
about 1000 ohms If the skin barrier is overcome,
the resistance drops to the internal body
resistance about 400-600 ohms from head to
foot about 100 ohms from ear to ear. Let's
assume the skin barrier has been broken so the
effective body resistance is about 500 ohms.
The 120 V ac from a wall outlet will induce a
current flow of 240 mA, over twice that needed
to cause death through ventricular fibrillation.
circuit breakers typically trip at 15 A
so this flow through the body will be
uninterrupted by the circuit breaker.
Argon-ion lasers 600 V DC, 50 Amps DC
Body resistance will let only 0.5-5 Amps go
through you
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High Voltage Hazards
The most common laser-related cause of
death Even though the power is turned off, some
devices (e.g. capacitors) are still charged Do
not disable enclosure safety switches/interlocks
Do not wear anything metal like a ring, bracelet,
watch, belt buckle, earrings, or keys Never
stand on a wet surface
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Fire Hazard
Fire hazards The solvents used in dye lasers
are flammable. High voltage pulse or flash lamps
may cause ignition.
Electrical circuits Improper beam
enclosures Ignition of gases / fumes Flammable
solvents Provide a beam absorber behind the
workpiece and around it Put a shield between
yourself and the workpiece
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Fume Hazard
Some materials, such as certain plastics, emit
toxic gas when they burn under a laser
beam Consult the manufacturer of material Turn
on ventilation system (Vacuum)
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Other Hazards
Skin Burning at high power CO2 lasers,
excimer lasers. Chemical Halogen
gases in excimer lasers are toxic, do not ingest
dyes from dye lasers, etc.
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IPH Case Studies
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IPH Case Study October 16, 1972 Half of His
Cardiac Muscle Was Burned
Person MIT grad student in IPHs laser
group. Problem Plastic guards on floating
external electrodes for his HCN laser were not in
place. Outcome He accidentally made contact,
was electrocuted. IPH attended memorial service
two days later on his 21st birthday.
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IPH Case Study I Felt Something Was Wrong
Person IPH, circa 1980. Problem Using hands
to change components after testing pulsed CO2
laser high voltage power supply with internal
probe repeated many times in an hour one time
his colleague said the voltage was
off. Outcome Something inside me told me not
to believe him. I was right. I wasnt zapped.
(argon-ion laser power supply is shown)
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IPH Case Study To His Minds Eye
Person Columbia undergrad working with IPH at
LLNL circa 1982. Problem He knew he wasnt
supposed to look directly at the argon-ion laser,
but why couldnt he use a dental mirror to view
it? Outcome Colleague stopped him in the nick
of time.
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IPH Case Study He Burnt His Fovea and Now is
Blind in One Eye
Person LLNL (Ph.D.) employee (IPH friend) very
experienced with lasers, 1984. Problem
Rushing alignment of NdYAG laser, just before
leaving LLNL for a faculty position. Outcome
He put his eye to close to the beam it burnt
through his eye goggle and reflected off the side
into his fovea. Now he is blind in that eye.
Laser goggles are not always the whole answer.
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IPH Case Study The Room is On Fire
Person Lab near IPH office, 1 week before IPH
left LLNL for Columbia in 1986. Problem
Flashlamp blew in flashlamp-pumped dye laser, and
dye solvent caught on fire. Outcome Lab
fire, all safe, IPH saved his books and papers
(from the water from the sprinklers).
Flash-pumped dye lasers are a fire waiting to
happen and are now not that common.
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non-IPH Case Studies
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Los Alamos lab chief halts all work Lapses in
security, safety prompt angry message to
staff Keay Davidson, Chronicle Science
Writer Saturday, July 17, 2004
http//www.sfgate.com/cgi-bin/article.cgi?f/c/a/2
004/07/17/LABS.TMP
The "mess" includes not only security but
safety lapses, as well. The Chronicle learned
late Friday that a 20-year-old student intern at
the lab suffered a severe eye injury Wednesday
while she was working with a laser. The woman was
being taken to Johns Hopkins medical center in
Baltimore for treatment to save her vision. The
laser accident is just one of a number of recent
safety incidents at the lab -- for example, a
"near-miss" in which staffers might have been
electrocuted -- that have stunned and angered
Nanos, lab spokesman Jim Fallin told The
Chronicle. In a phone interview late
Friday, Los Alamos spokesman Fallin said that at
about 130 p.m. Wednesday, the intern "was
working on a series of experiments involving a
class-4 pulsed laser." When the experiments were
over, she remained for a time in the lab,
thinking the laser -- whose light is not visible
to the naked eye -- was turned off. In fact,
the laser was continuing to emit its intense,
although invisible, rays. Somehow the rays
penetrated her eye. "About 30 minutes later,
she experienced blurred vision," Fallin said.
Doctors discovered she has a "lesion to her
retina in her left eye. ... There was also some
hemorrhaging in her left eye."
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Four fired over Los Alamos scandal Wednesday,
September 15, 2004 Posted 843 PM EDT (0043 GMT)
http//www.cnn.com/2004/US/09/15/los.alamos.securi
ty.ap/
ALBUQUERQUE, New Mexico (AP) -- Four Los Alamos
National Laboratory workers were fired and one
will resign under pressure for their roles in a
security and safety scandal at the lab, the lab's
director said Wednesday. The fired workers were
among 23 suspended this summer after two computer
disks containing classified information went
missing and an intern was injured in a laser
accident. The discovery of the missing disks July
7 prompted a virtual shutdown of the nuclear lab,
idling roughly 12,000 workers. Three of the
workers will leave the lab in connection with the
missing computer disks the other two were
involved in an accident in which a laser injured
an intern, he said.
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165 Frequency doubled NdYAG in a research
lab. A visiting professor from China lost part
of the sight in his left eye after he removed his
safety goggles during a test with a frequency
doubled NdYAG laser. The professor was in the
research lab of a university. He was working on
an experiment with a crystal he had grown. He had
removed his goggles so he could see better and
the laser reflected into his eye, burning the
retina.
http//www.rli.com/accident/case_studies/
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What happens when you cant see the laser?
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255 Beam blinds scientist doing alignment of a
NdYAG laser. During optics alignment involving
a 30 mJ pulsed NdYAG laser (1064 nm,10 Hz) on a
target using a prism, the beam exceeded the
prism's critical angle and struck the scientist
in the eye resulting in a permanent retinal burn.
Unfortunately, no protective eyewear was worn at
the time. An ophthalmologist was consulted and
confirmed retinal burns. Blurry vision resulted
especially when reading.
http//www.rli.com/accident/case_studies/
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274 Technician receives retinal burn with a
single Ti-Sapphire laser pulse. A laser lab
technician was working without laser protective
eyewear. He was exposed to a single 7 ns pulse at
a pulse energy of 10-50 µJ. In the setup, the
beam was directed onto a metal "test slide" from
the power meter manufacturer. This was used to
test whether the beam would harm the power meter.
The slide was accidentally tilted so-as-to
reflect the beam into technician's eye (assume
about 4 reflection). At time of exposure the
person perceived a bright flash that persisted
(with eyes closed) as if he had looked at the
sun. There was no pain nor did the person go into
shock. There was eyewear was available but not
for the 806 nm wavelength in use. (in 1996)
http//www.rli.com/accident/case_studies/
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280 Graduate student receives macular lesion
from picosecond laser. A picosecond NdYAG
pulsed laser operating at 1064 nm was on a laser
optics table. The beam was directed from one
table to another across an isle. The beam went
onto the second table, where it was directed onto
a liquid sample holder. Here, apparently, the
beam was bigger than the liquid sample holder, so
the edges of the beam went past the sample bottle
and then off that table into the room area where
a Strip Chart Recorder (SCR) was located. A
graduate student working on the experiment looked
at the SCR and received about 10 of the beam
into the eye. The student reportedly a "heard a
popping sound" which was followed by a white spot
in the vision center. The professor took the
student to an eye doctor for a retinal exam which
confirmed the burn exposure. The student did not
experience shock. The beam caused a retinal burn.
The student now complains that his "eyes get
tired" while reading.
http//www.rli.com/accident/case_studies/
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307 Backscatter from mirror causes hemorrhage
and foveal blindspot. A 26 year old male
student aligning optics in a university chemistry
research lab using a "chirped pulse"
Titanium-Sapphire laser operating at 815 nm with
1.2 mJ pulse energy at 1 KHz. Each pulse was
about 200 picoseconds. The laser beam
backscattered off REAR SIDE of mirror (about 1
of total) caused a foveal retinal lesion with
hemorrhage and blind spot in central vision. A
retinal eye exam was done and confirmed the laser
damage. The available laser protective eyewear
was not worn. (in 1996)
http//www.rli.com/accident/case_studies/
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What happens when you cant see the laser?
Laser goggles help.
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From the LBL Safety Manual LASER ACCIDENTS IN
RESEARCH CASE REPORTS This appendix outlines five
real accident cases. Four are from a research
setting, and one is from the medical area. Case
1. Electrical Laser Accident A researcher was
working on a home-built 5-watt CO2 laser,
replacing and tuning a new tube. The system was
obtained from another group. The researcher was
unaware that the end caps were energized and,
during the tuning process, he made contact with
the palm of his left hand on the end cap and his
thumb on the (ground) support bar. He received a
painful shock from approximately 15,000 volts at
20 mA DC. The researcher was treated for injury
to his hand and wrist, and the pain (severe)
lasted several days. Once again these nonbeam
hazards can be the deadliest and tend to sneak up
on one, for the user is not focusing on them
while involved in other activities. This is
especially true when working on equipment one is
not completely familiar with.
http//www.lbl.gov/ehs/pub3000/Ch16_AppF.html
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Case 2. Los Alamos Laser Accident A postdoctoral
employee received an eye exposure to spectral
radiation from an 800 nm Class 4 laser beam. The
extremely short pulse (100 fs) caused a
100-micron-diameter burn in the employee's
retina. The accident occurred shortly after a
mirror was removed from its mount and replaced
with a corner cube during a realignment
procedure. Although the beam had been blocked
during several previous steps in the alignment,
it was not blocked in this case. The employee was
exposed to laser radiation from the corner cube
mount when he leaned down to check the height of
the mount. Neither of the two employees
performing the alignment was wearing the
appropriate laser eye protection. The system had
two modes of operation 10 Hz and 1,000 Hz. In
addition, the researcher forgot that the part of
the 800 nm beam he could see represented only
1-2 of the beam.
http//www.lbl.gov/ehs/pub3000/Ch16_AppF.html
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Case 3. Livermore Falcon Project Laser Accident A
researcher was working alone in the Falcon laser
laboratory (an activity in the Physics
Directorate), aligning a NdYLF laser producing
40 mJ pulses at 1 Hz and 1,053 nm. Falcon is a
Tisapphire laser using chirped pulse
amplification and pulsed recompression to produce
peak-power levels in excess of 20 TW. Falcon will
interact with a pulsed high-current 100 MeV
electron beam to generate subpicosecond pulses of
keV radiation. At the time of the accident, two
lasers were operating a 820 nm Tisapphire and a
532 nm pumped NdYAG operating at 10 Hz and 100
mJ/pulse. The researcher had "lowered" his
eyewear to aid him in alignment. As he was
placing a sensor card in the beam he heard a
noise from somewhere the lab. He walked around
the optical table to investigate and was struck
by a stray laser beam that came off a polarizer
deflecting the laser from the plane of the table.
The researcher had removed a beam block from the
polarizer to clean it and had failed to replace
it this was one of several stray beams in the
lab. The researcher received an injury to his
right eye from a single-pulse 1.6 mJ, 10 ns,
1.053 nm beam. The system was in low-power mode.
He broke several blood vessels in his eye,
resulting in blood pooling and obstruction of
vision. He had a damaged area of 800 microns in
his eye. This group had been warned earlier about
failure to wear eyewear. The lead researcher took
the position that experienced users could operate
without eyewear in low-power mode, despite the
fact that it violated their SOP. Plans to install
beam enclosures and beam blocks had been put off
by the lead researcher until program milestones
were achieved.
http//www.lbl.gov/ehs/pub3000/Ch16_AppF.html
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Case 4. Brookhaven National Laboratory On April
22, 1999, at the Brookhaven National Laboratory,
safety personnel found that a laser interlock for
an experiment on one of the beam lines at the
National Synchrotron Light Source had been taped
closed, thus allowing bypassing of the intended
interlock function. Two visiting researchers
(trained and qualified in the use of the laser)
had bypassed the interlock to determine if the
laser was operating properly. While the
interlock, which prevents personnel exposure to
the laser beam, was bypassed, the researchers
held a screen that was sensitive to the laser
wavelength in the path of the laser beam and
watched the screen fluoresce. The laser operating
procedure clearly states that bypassing the
interlock is forbidden. (ORPS Report
CH-BH-BNL-NSLS-1999-0003)
http//www.lbl.gov/ehs/pub3000/Ch16_AppF.html
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Case 5. Airway Fire During laser surgery on a
patients vocal cords, the surgeon struck the
endotracheal tube with a pulse from a CO2 laser.
The tube, which carries oxygen to the patient and
runs through his mouth to his lungs, was not made
of laser-resistant material. Instead, it was made
of polyvinyl chloride (combustible to both NdYAG
and CO2 lasers). It caught fire and filled the
mans lungs with toxic smoke, causing burns. The
patient did not survive the procedure. In
general the anesthesiologist has only six seconds
to recognize that a tube has ignited and remove
it before the fire peaks. Once ignited, the tubes
are as hot as an oxygen lance used in welding.
Oxygen flow through tubes can be up to 40 liters
per minute. The flame can reach a length of 5 to
10 inches. Laser beam interaction with secondary
materials is a known source of laser incidents.
This sort of unplanned interaction is a danger
one needs to think of beforehand. Laser safety is
not just wearing the correct eyewear.
http//www.lbl.gov/ehs/pub3000/Ch16_AppF.html
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Observations and Closing Remarks
You are responsible for your safety and for
everybody elses. Laser beams enclosed. Beams
stay on table. No stray reflections. No lasers
across beam paths (or enclose paths). No sitting
in the lab. Zero tolerance policy. (All lasers
treated the same, i.e. with caution.) Laser
Goggles but you need to see beam in vis (2l?)
need help in uv/ir. Flashing lights and warning
signs. Work with a partner on power supplies,
turn off the circuit breaker. Never hurry. No
shortcuts. Dont stick your head into the beam
path. Dont lean over the beam path. Watch out
for that upward reflection! If you are out of
it, tired, sleepy, or having a bad day, get out
of the lab. Even experienced laser people make
mistakes! Common Sense (and a Sense of
Responsibility)
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Safety is 5 knowledge and 95 common sense and
responsible behavior.
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Sources include University of Pennsylvania
Laser Safety Manual http//www.ehrs.upenn.edu/prog
rams/laser/default.html Marc Vrakking FOM
Instituut for Atomic and Molecular Physics
(AMOLF) Laser Material Processing Lab Department
of Welding Engineering The Ohio State
University LBL Health Safety Manual
http//www.lbl.gov/ehs/pub3000/pub3000c.html Chap
ter 16 http//www.lbl.gov/ehs/pub3000/CH16.html
Rockwell Laser Industries http//www.rli.com/acci
dent/case_studies/