The College Laser Safety Officer (SLSO) oversees all
matters concerned with laser safety within the College and liaises with both the
University Radiation Protection Officer and with specific Laser Safety
Supervisors (LSS) within the College who are responsible for safe Schemes of
Work and supervision in their specific areas. Terms of reference for and
responsibilities of the College Laser Safety Officer, and Laser Safety Supervisors are
contained within University of Exeter Local
Rules for the use of Lasers and the Association of University Radiation
Protection Officers “Guidance
on the Safe Use of Lasers in Education and Research”.
Risk Assessments must be performed, and Local
Rules and Schemes of Work must be written for each sphere of work involving
lasers of classes 3B and 4. These rules should be brought to the attention of
all employees and students who may be affected by them and should be displayed
at each work area. These rules may in the first instance be drawn up by the
user of the laser, but they must be approved and ratified by the SLSO and/or
the LSS. It is the duty of the Head of College through his SLSO and LSS to
ensure that the Local Rules are adhered to, and that all persons working with
lasers in his College are properly trained in their use. It is the duty of each
person whose work involves a laser to ensure that the Local Rules and safety procedures
are adhered to.
All
working laser systems purchased from a manufacturer must carry a label stating
the class of that system. This should not be removed or altered in any way
unless the system is itself modified in such a way as to alter its class.
Should this be done, the Laser Safety Service must be consulted over the
reclassification of the system. In line with variously agreed national and
international standards all lasers are assigned an appropriate classification.
The criteria for the assigning of a class to a laser system are complex. A
broad indication of the meaning of the class and the implications for the
system it describes are contained within the Local
Rules for the use of Lasers and the Association of University Radiation
Protection Officers “Guidance
on the Safe Use of Lasers in Education and Research”, and are summarised
briefly below:
.
- Class 1. Lasers that are safe under
reasonably foreseeable conditions of operation.
- Class 1M. Lasers which are safe under
reasonably foreseeable conditions of operation, but may be hazardous if
the user employs optics within the beam
- Class 2. Lasers that emit visible
radiation in the wavelength range from 400 nm to 700 nm where adequate eye
protection under reasonably foreseeable conditions is normally afforded by
aversion responses, including blinking.
- Class 2M. Lasers as per Class 2 but
viewing of the output may be more hazardous if the user employs optics
within the beam.
- Class 3R. Lasers where direct intrabeam
viewing is potentially hazardous but the risk is lower than for Class 3B
lasers.
- Class 3B. Lasers which are normally
hazardous when direct intrabeam exposure occurs
- Class 4. Lasers that are also
capable of producing hazardous diffuse reflections. They may cause skin
injuries and could also constitute a fire hazard. Their use requires
extreme caution.
For rule-of-thumb purposes, for continuous-wave
lasers, Class 2 lasers are powered below 1 mW, Class 3R lasers between 1 and 5
mW, Class 3B lasers between 5 and 500 mW, Class 4 lasers anything above this
power.
A central register of lasers is maintained by
the University Radiation Protection Service. In order that this may be kept
up-to-date, the University Radiation Protection Officer (URPO) must be advised IN
WRITING of the arrival of any new laser, and its situation, by the College
Laser Safety Officer. The URPO will wish to inspect the installation of any
newly-acquired or re-sited laser of class 3B or 4. Any laser manufactured on
the University premises must be reported to the URPO before it is made
operational, and again when it becomes operational, so that it may be entered
on the inventory, and its output and labelling checked.
Before any new laser experiment is performed, or
new laser of class 3B or 4 taken into use, a full Hazard and Risk Assessment
must be made, and the successful completion of this must also be confirmed to
the URPO.
All lasers must bear warning labels, and it is
the responsibility of the purchaser or maker to ensure that these are affixed.
The University Radiation Protection Service can advise and provide labels where
necessary. The required labels are:
- A "Triangle and
Starburst" label.
- A label stating the class of
laser.
- A label listing any hazards
associated with the radiation.
- A label detailing the output of
the laser (wavelength, visible/invisible, etc)
- A label indicating (preferably
with an arrow design) the laser aperture.
The door of any laboratory where a laser of
class greater than 1 is installed for use must bear a
"Triangle and Starburst" warning
label. If a laser of class 3B or 4 is installed for use, this warning label
must in addition bear the legend, "DANGER, laser beam", and
the door must bear a notice stating the class of laser present.
No warning label is required on the door of any
room where a laser of class 1 or 2 is in use temporarily for setting-up,
alignment or demonstration purposes. However, all normal precautions must be
taken to avoid accidental exposure of any eye to the beam.
- Before using any laser,
ascertain its class and acquaint yourself with the special rules and restrictions
which apply to that class of laser. Ensure that you have studied any Risk
Assessment and experimental protocols relating to the laser (these should
exist for any laser of class 3B or 4).
- Under no circumstances may the
output of a laser be viewed along its beam-path either directly, by specular
reflection or with the aid of an optical instrument. In other words, NEVER
LET A LASER BEAM ENTER YOUR EYE.
- Always ensure that the laser
beam cannot extend beyond its useful limit. A suitable beam-stop must be
used to prevent the beam from leaving the experimental area.
- Do not use a laser of a higher
class than is necessary for the purposes of the experiment.
- Do not tamper with an
experimental setup in such a way as to negate the safety precautions and beam-limiting
devices that have been incorporated.
- Where an instrument
incorporates a laser whose beam-path is protected by shielding and interlocks,
DO NOT UNDER ANY CIRCUMSTANCES interfere with or attempt to
override those precautions.
- At the conclusion of an
experiment, ensure that the laser is switched off or returned to a safe condition.
NEVER LEAVE AN ACTIVE LASER UNATTENDED.
- Never forget that a laser is a
potentially dangerous power-source, and not a toy. Anyone found misusing a
laser in any way will be subject to disciplinary action, and may be
prevented from further use of lasers.
- Always remember that you are
responsible for the safety of others as well as yourself.
- Always design and operate
experiments in such a way as to eliminate all foreseeable dangers.
- Guard against other,
non-optical hazards associated with lasers, such as high voltage
electricity, charged capacitor-banks, toxic chemicals for dye-lasers etc.
No undergraduate may have access to, or use,
these classes of laser. A hazard and risk assessment MUST exist for every
laser of these classes. The design of the laboratory in which the laser is used
should incorporate:
- complete absence of all
specularly-reflecting surfaces (e.g. mirrors, glass-doored cupboards, bottles,
polished apparatus, beam-path element holders, etc.) that are not an
integral part of the beampath or experimental equipment.
- a high light-level, enhanced by
light-coloured walls. This has the dual effect of making the laboratory
safer to move around in and of ensuring that the pupils of the eyes of all
workers are as far closed as possible to restrict the aperture of the
eyes.
- a light system outside the
laboratory door to warn unauthorised persons against entering the experiment
zone. These should be interlocked with the laser switching circuitry, and
fail-safe in design. A system of interlocked and fail-safe switches on the
access doors either to switch off the laser or release shutters to occlude
the accessible beam in the event of unauthorised access is desirable, but
may not be appropriate in all cases.
All users of these classes of laser must be
registered with the University Radiation Service as laser users, and must
undergo training in the use of the laser to which they are registered,
including the correct operation of safety procedures and interlocks. No
ophthalmic testing is required. All new workers must sign a declaration that
they have received training and have read and agree to abide by the relevant
instructions and rules.
As far as is consistent with ease of use and
safe handling, the beam-path of these classes of laser should be enclosed when
the laser is in operation. Where this is not possible, guard-rails or screens should
be provided to prevent accidental access to the beam. These lasers may never be
operated hand-held; they may only be operated when secured in the required
position.
The use of laser goggles is dependent upon the
particular circumstance. While they can act as a
safeguard, especially for onlookers, they can
create a false sense of security, and by rendering a
visible beam invisible can in fact create a
hazard. However, when setting-up or aligning an open beam and in all cases when
working with beams of wavelengths outside the visible spectrum, the use of the appropriate
laser goggles is recommended.
Lasers of these classes must incorporate a
key-switch to which only authorised users are issued the key. Keys must not be
left permanently in the switch when the laser is not operating.
Laser pointers in Classes 1 and 2 will not be
subject to registration when used for teaching purposes. Laser pointers in Class
3R must be registered with the University Radiation Protection Service. Registration
will be limited to members of staff and Ph.D. and equivalent students whose
application is supported by the College. Pointers in these classes have the
potential to cause serious irreversible damage to the eye and there are strict
rules governing their use (refer to the guidance documentation as before for
non-ionising radiation, available from the documentation page of
the Health, Safety and Environment Office website.
Laser pointers in Class 3B and abovewill
not be registered or permitted for use by the University.
Although most laser pointers are marked with a
class number, there have been instances of pointers exceeding the stated class.
Also, American classification differs somewhat from the European system. The University
Safety Office has equipment to measure the power output of lasers, and will be
pleased to help where doubt exists.
Apart from
the risk of electric shock and burns arising from direct contact with the
equipment, radio-frequency heating coils are hazardous in that they can induce
dangerous voltages and heating currents in neighbouring conductors. Suitable
screens should be provided to avoid dangerous voltages being induced in
neighbouring metallic equipment which should also be effectively earthed. All
metal ornaments such as rings, watches etc should be removed from the hands and
wrists when working with radio-frequency heaters.
Ultra-violet
radiation shorter than approximately 340nm is extremely damaging to the eyes.
Conjunctivitis generally results 4-8 days after exposure. Ultra-violet sources
should always be properly shielded and eye protection worn by those working in
the immediate vicinity of exposed sources. The principal sources of UV
radiation are ultra-violet lamps, such as those used for sterilisation and
electric arc welding.
