EH-17 Laser-Equipped Weapons: Clarifying Eye Safety Issues
                          ENVIRONMENT, SAFETY & HEALTH

                                   BULLETIN

Assistant Secretary for                              U.S. Department of Energy
Environment, Safety, & Health                        Washington, D.C. 20585

DOE/EH-0020                      Issue No. 17                    November 1986

Laser-Equipped Weapons: Clarifying Eye Safety Issues

Laser equipment is being used at DOE facilities
to train security forces and couriers.
Questions about eye safety and applicable
standards abound.  This bulletin will answer them.

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MILES and ESS

The only way to train armed forces used to be with controlled live fire.  By
the late 1970's, however, the U.S. Army had developed semiconductor laser
equipment that could simulate live fire.  Called MILES (Multiple Integrated
Laser Engagement System), it was used primarily to simulate the long-range
weapons used in large battlefield engagements.

During the early 1980's, Sandia National Laboratories adapted MILES equipment
for the small-forces and close-in engagements which typically might be
encountered while protecting DOE facilities.  Since then, newer equipment
based on those modifications has been manufactured.  It is called ESS (for
Engagement Simulation System).

Some confusion exists because those who have worked with laser-equipped
weapons for some time often refer to all such weapons as MILES, much like
photocopiers are often referred to as Xeroxes.  Most DOE contractors are using
ESS equipment although some DOE-modified MILES and some original (unmodified)
MILES equipment is still being used.

MILES and ESS use the same technique.  A small solid state laser transmitter
attached to each weapon shoots pulsed messages of invisible (904nm) laser
light when a blank round is fired.  Each pulse has two levels of brightness -
a high level for "near miss" and a lower level for a direct hit, or "kill."

Each trainee wears a detector harness which covers the upper torso and head.
It contains infrared detectors sensitive to the specially coded laser
"bullets."  When a beam strikes a detector harness, a small speaker on the
shoulder emits either a warbling sound for a near miss (a whistling bullet)
or a continuous unpleasantly loud sound for a direct hit.  If hit, the
trainee removes a key from his transmitter unit (disabling it) and inserts it
into a control box also on his harness.  Thus, he is taken out of the
exercise.  Only the trainer or control umpire can reset the trainee's harness
with his own transmitter, or "controller's gun."

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 o Know your equipment - is it FDA certified?

 o Have you applied the necessary ANSI controls - Class I for field use
   and Class IIIb for maintenance?
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Eye Safety

Obviously, the many hazards associated with running, crawling, climbing
fences, noise, and handling explosives and blank ammunition are also present
during training exercises.  The special issue of eye safety arises because
the laser beams in MILES and ESS equipment are aimed directly at people.

Overexposure during training is considered improbable, however, since any
exposure would be of very short duration.  The total pulsed message lasts
only .48 seconds and it is unlikely that more than a few of its
10-to-the-minus-7 second-long pulses, fired from the hand-held weapon, would
enter the iris of a moving person's eye.  Overexposure would be more likely
during repair, calibration, and maintenance, when power to the laser diode
might be increased.

Laser Equipment Must Comply With FDA and ANSI Standards

By law, all equipment manufactured or sold in the U.S. that contain lasers
(including laser diodes) must be certified by the FDA against 21 CFR, Part
1000, "Radiological Health," and Part 1040, "Performance Standards for
Light-Emitting Products."  This regulation classifies lasers into four
categories: Class I is the least hazardous and is termed "eye-safe;" Class IV
is the most hazardous and requires special warning labels and physical
protection.

In addition to FDA requirements, DOE prescribes (in Order DOE 5480.4)
American National Standard Institute's "Z136.1 for the Safe Use of Lasers."
This industry consensus standard establishes exposure limits and procedures
for the safe operation of lasers.  It includes a classification scheme
similar to the FDA's which applies to lasers built by users (i.e., in a
research and development laboratory).

There are some differences between FDA's and ANSI's classifications for
repetitively pulsed lasers, causing confusion about which classification is
proper for MILES and ESS gear.  The FDA classifications take precedence over
ANSI classifications for all commercial devices such as MILES or ESS gear.

FDA: 21 CFR, Parts 1000 and 1040: A manufacturer or U.S. distributor of laser
devices must: 1) register his units with the National Center for Devices and
Radiological Health (NCDRH), certifying the class of operation of each unit;
and 2) properly label each unit.

DOE has found that not all manufacturers of MILES and ESS equipment are in
compliance.  The issue of being certified by the FDA became clouded in the
recent past because the original MILES equipment was exempted from FDA/NCDRH
regulations.  Instead, this equipment was (and still is) regulated by a
Defense Department laser safety program which is equivalent to FDA's.
Apparently, some suppliers do not realize that the exemption applies only to
MILES equipment sold to the Department of Defense.

All laser products purchased by DOE or DOE GOCO contractors must be
registered with the National Center for Devices and Radiological Health.

According to some FDA officials, adverse action for noncompliance (recall,
imposition of fines, etc.) is unlikely so long as the supplier is reasonably
expedient about rectifying the situation.  Suppliers should be advised that
certification is relatively straightforward but does include filling out the
appropriate reports, keeping accurate records, labeling the units to show
their class of operation, etc.  Measurements made by EG&G Energy
Measurements, Inc., using NBS traceable lab equipment, showed that all ESS
equipment now manufactured, with the exception of the Wide Angle Laser
Transmitter (WALT)*, meet FDA Class I criteria.

All current DOE suppliers have been notified and will be registering ESS
devices with the NCDRH certifying that accessible emissions meet Class I
criteria.  For those who are already using uncertified units, a step by step
procedure for certification can be obtained from:

  Office of Compliance (HFZ-300)
  Center for Devices and Radiological Health
  Food and Drug Administration
  8757 Georgia Avenue
  Silver Spring, Maryland
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*Also known as the Claymore Land Mine Simulator.  These units use an array of
laser diodes operating at very high power levels (in excess of Class I
levels) to generate large sprays of "kill" signals that simulate shrapnel
generated by land mines.  These units should be used only under strict field
administrative controls required by ANSI Class IIIb criteria.  A new second-
generation design, presently being developed, will meet FDA Class I
standards.


Note: EG&G Energy Measurements, Inc. will help with the certification
process.  Contact: John P. Jekowski (505-846-0125) or Dave Hutton
(505-846-3447).
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ANSI Z136.1 for the Safe Use of Lasers primarily addresses safe operating
procedures for the various classes of lasers but it also includes
classification criteria for user-built devices (which are not covered by FDA
regulations).

The FDA and ANSI standards were developed together in the early 1970's and
were identical when published in 1976.  In 1980, however, after studies
showed that repetitively pulsed lasers were more damaging to the retina than
had been expected previously, the ANSI exposure limits were made more
stringent by incorporating repetitively pulsed correction factors.  Since
1980, 1 watt gallium arsenide lasers have been common in both fiber optic
communication systems and in laser engagement systems and more recent animal
studies have been conducted to determine effects on the eye.  In these recent
studies, damage to the retina was observed only with sustained exposures at
power levels higher than 10 watts.

Based on this new data, the ANSI committee recently raised (made less
stringent) the Maximum Permissible Exposure (MPE) limits for repetitively
pulsed infrared lasers by approximately a factor of three.  This change will
be published soon in the 1986 version of the standard.  Under the 1986
standard, use of ESS units, with the exception of WALT units, would not
result in exposure above the ANSI MPE.  Until the new standard is published,
the Assistant Secretary for Environment, Safety, and Health has granted a
temporary exemption (until January 2, 1987) allowing DOE contractors to use
ESS and modified MILES equipment without laser eye protection during tactical
training.

A Discussion of Power Output

When triggered by a blank round, the MILES and ESS transmitters send a
message of 100 nano-second pulses emitted at the rate of 1636 pulses per
second for 0.48 seconds.  The maximum radiance of MILES and ESS gear occurs
at about 1-1/2 meters in front of the device, and is created by the optics
used to diverge the laser light so that the range of the signal simulates a
bullet.  The maximum radiance is 120 nano Joules per pulse, thus the total
output in a single "round" is:

1.2 x 10-to-the-minus-7 J/pulse x 1636 Hz x 0.48s = 9.4 x 10-to-the-minus-5 J

(although only 2/3 of this energy will pass through a 7mm aperture, the
maximum size of a human iris).

The FDA accessible emission limit (AEL) for 904nm wavelength light is:

1.74 x 10-to-the-minus-3 x t-to-the-3/4 where t is time.

Assuming t = 0.48 seconds, the AEL is:

1.74 x 10-to-the-minus-3 x (0.48)-to-the-3/4 = 1.0 x 10-to-the-minus-3 J.

The ANSI 1986 MPE for 904nm wavelength light is:

1.28 x 10-to-the-minus-6 x N-to-the-3/4 J/cm2 where N is the number of pulses.

Assuming a 7mm aperture for a fully dilated pupil, the MPE is:

1.28 x 10-to-the-minus-6 x (1636 x 0.48)-to-the-3/4 x .385cm2 =
      7.2 x 10-to-the-minus-5 J

The ANSI standard requires one to consider the possibility that optical
devices may be used.  In this case, the device would be binoculars which are
issued for training exercises.  Light could be collected in the 50mm
apertures of binoculars and focused into the eye.  The MPE must then consider
the transmitter's total output (9.4 x 10-to-the-minus-5 J in .48 seconds) as
entering the pupil.

The worst case - an individual standing 1-1/2 meters in front of a device and
viewing the whole half second message through binoculars - would exceed the
MPE.  However, hazard analyses have concluded that it is extremely unlikely
that the beam would focus into a pupil for a half second when, during
training exercises, both the person holding the weapon emitting the beam and
the person looking through the binoculars are in almost constant motion.  Even
when standing still, the hands of both people would jiggle so much naturally

that it is unlikely that the beam could focus into the pupil for even a half
second, especially considering the recoiling action of the weapon.  To that
improbability must be added the fact that binoculars cannot be made to focus
on an object only 1-1/2 meters away.

Additional Labeling Is Recommended

Even though these laser devices meet Class I criteria and are "eye-safe," DOE
suggests that in addition to the label affixed by the manufacturer, a
modified ANSI-type CAUTION label be applied to all laser transmitters.  It
should state that invisible laser radiation is present and advise the user
not to stare directly into the beam if within three meters of the equipment
and not to use optical instruments (such as binoculars) within 20 meters.  A
grey and black label (not the standard red and white label) would permit this
equipment to be used during camouflaged conditions.

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Note: Labels are available from EGG/EM, Kirtland Operations.
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During Maintenance, Power Levels Can Be Class IIIb


Internal circuitry is adjusted during the manufacturing of MILES and ESS
equipment to establish a Class I level of operation.  This power level is
checked periodically prior to use and following any repair.  If, during
repair or maintenance, the internal circuitry is adjusted improperly, power
can be emitted at a level as high as Class IIIb.

Therefore, during calibration, repair, and maintenance, it is important to
take the special control measures outlined in the ANSI standard Class IIIb
criteria.

In particular:

o  technicians must wear proper eye protection

o  warning signs must be posted in the adjustment area

o  optical and electronic equipment used to make adjustments must be
   traceable to the National Bureau of Standards

o  appropriate logs must be kept to provide an audit trail for adjustments.


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Information for this Bulletin was provided by John (Jack) Jekowski and David
Hutton, both of whom work for EG&G Energy Measurements, Inc., Kirtland
Operations, Albuquerque.  Mr. Jekowski is Assistant Program Manager for
Safeguards and Security and Dr. Hutton is Manager of the Sciences Department.


Bulletin is published so that DOE program managers and contractors can share
information about potential occupation safety problems relevant to DOE
operations.  For more information or additional copies, contact Nona Shepard,
Editor, Office of Operational Safety, Assistant Secretary for Environment,
Safety & Health, U.S. Department of Energy, Washington, D.C. 20545, telephone
FTS 233-2958; Commercial (301) 353-2958.
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