Risk Management Services
www.riskmanagement.ubc.ca
Laser Safety and Program Development
Control Measures
Engineering Control Measures
There are several engineering controls used to keep people
around the laser safe:
Beam housings
Attenuators
Interlocks
Shutters
Remote firing controls
Example:
Curtains between laser areas
Laboratory Door Interlock
Interlocks on laboratory doors may be connected to the laser remote
interlock connector or shutters on the laser output to terminate the
beam if the door is opened during laser operation. Such interlocks may
be non-defeatable or may be designed to be bypassed or defeated by
the laser operator. The use of such interlocks in a controversial topic.
Some Department of Energy laboratories require such interlocks for all
class 3b and class 4 lasers, but others do not.
Laboratory Door Interlock (cont.)
The ANSI Standard states that procedural entryway safety controls may
be used where safety latches or interlocks are not feasible or are
inappropriate. The conditions under which interlocks are
inappropriate are debatable.
The OSHA Technical Manual allows procedural entryway controls as an
acceptable alternative. It states: A blocking barrier, screen, or curtain
that can block or filter the laser beam at the entryway may be used
inside the controlled area to prevent the laser light from exiting the area
at levels above the applicable MPE level. In this case, a warning light or
sound is required outside the entryway that operates when the laser is
energized and operating. All personnel who work in the facility shall be
appropriately trained.
Entryway Warning Lights
Entryway Warning Lights
Laser warning lights are required at the entryway of permanent class
4 laser controlled areas if the doors are not interlocked.
If the doors are interlocked, lights are not required, but they are often
installed.
The most common light arrangement is the three light system. Two
light systems with red and green lights only are also common.
In many cases a single light indicates laser operation. If a single light
is used, it should flash during laser operation.
Such flashing lights are usually red, but a flashing blue light
sometimes indicates laser operation in facilities where flashing red
lights have another specific meaning.
Laser Protective Barriers
Photos courtesy of
Laser Protective Barriers
Laser protective barriers are often used to enclose laser hazards
when an industrial laser system must be operated with the
beam exposed during maintenance or service.
Laser protective barriers and curtains can also be used to limit
the NHZ inside laser controlled areas.
These barriers are often used to protect entryways, computer
work stations, and workbenches where workers may not always
wear protective eyewear.
It is especially important that no direct optical path exist
between laser optics tables and computer stations in laser
laboratories.
Curbs on Optical Table
In this experiment all beams are horizontal and 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.
Beam Control
Beam Control
It is important to limit the NHZ inside laser controlled areas.
The use of beam blocks, beam tubes, partial enclosures,
and curbs on optical tables greatly enhance safety in laser
laboratories.
In many cases the NHZ can be confined to the area of optical
tables.
It is not necessary to interlock all enclosures inside laser
laboratories, but appropriate labels should always be applied to
alert workers to potential laser hazards.
Selection and Testing of Laser Guards
(enclosures, windows, etc.)
At low power levels, the selection of material and thickness of laser
shields is determined by the need to provide sufficient optical
attenuation. There is no concern about the shield integrity.
At high levels, the laser beam is able to destroy the guard material
and the laser radiation may penetrate the normally opaque shield
material. The integrity of the protective shields becomes a concern!
Laser
Computers in Research Labs
Allowing a direct view from a computer workstation into a laser
experimental setup increases the risk of eye exposure to reflected
beams.
There have been several accidental laser exposures because workers in
research laboratories removed their laser safety eyewear to better
observe displays on computer screens, and stray reflections from laser
experimental setups struck them in the eye. This risk is greatest when
using invisible beams or pulsed lasers.
Computers in Research Labs (cont.)
This risk can be eliminated by placing a
barrier between the laser setup and the
observer at the computer workstation.
Curtains or curbs on optical tables or
partitions around computers provide this
protection. Barriers providing protection
from laser reflections should be labeled.
It is not always practical to use barriers to
eliminate the possibility of reflected beams
at computer workstations in the laboratory.
Eyewear and procedural controls can be
used. However, users must make sure that
the procedures are always followed and the
eyewear is worn when required.
Administrative Control Measures
Administrative control measures include:
Warning signs/labels
Standard Operating Procedures (SOPs)
Training
CDRH Class Warning Labels
Laser Radiation
Do Not Stare Into Beam
Helium Neon Laser
1 milliwatt max/cw
CLASS II LASER PRODUCT
Class II
Class IIIa 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 IIIR with small beam
Class IIIb & Class IV
A CAUTION label means that a laser is visible and that it cannot deliver more
than 1 mW through the pupil of the eye. Only the aversion response is needed
for protection.
A DANGER label means that the laser is a class 4, a class 3B, or a class 3R that
has a small beam that can deliver more than 1 mW through a 7-mm pupil. The
class of the laser is stated in the lower right corner of the class warning label.
CDRH Class Warning Labels
Laser products are always labeled according to the requirements of the
federal standard. This means that many low power IR diodes that have
danger labels stating they are class 3B actually produce no hazard and
may be treated as class 1 lasers under the ANSI Standard. Examples of
this include diodes with wavelengths of 1.55 microns used in fiber optic
communications systems.
A 1 mW diode is labeled as class 3B under the federal standard, but it is
not really a hazard and can be treated as a class 1 under the ANSI
Standard. In fact, the ANSI class 1 limit is 9.6 mW. It is important that
workers understand the actual hazard associated with the lasers they are
using.
The power levels stated on class warning labels are often greater than
the laser can actually produce.
The correct values may be found in the printed product information.
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
Laser Safety and Program Development
Safety Practices
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
Administrative Safety Practices
Supervisors are responsible for training users
Standard Operating Procedures
Authorized personnel only in vicinity of laser
Designate NHZ for Class 3b and 4 lasers
Address non-beam hazards
General Safety Practices
Wear appropriate protective eyewear:
for appropriate laser wavelength
attenuate the beam to safe levels
comfortable enough to wear
Use minimum power/energy required for project
Reduce laser output with shutters/attenuators if possible
Terminate laser beam with beam trap
Use diffuse reflective screens, remote viewing systems etc.,
during alignments if possible
Remove unnecessary objects from vicinity of laser
Keep beam path away from eye level (sitting or standing)
Use specialized clothing if necessary (gloves, etc.)
Dont put your body parts
(particularly your eyes) in the beam!!!
Someone used a hand-held laser pointer to target a plane leaving
from the Calgary airport. (Canadian Press)
www. cbc.ca
10/16/2008
4th time that year in Calgary;
73 in Canada since 2005 just having some fun
(737 in UK in 2009)
