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School of Physics Safety Manual
>11. Non-Ionising Radiation
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School of Physics Safety Manual
The School Laser Safety Officer (SLSO) oversees all matters concerned with laser safety within the School and liaises with both the University Radiation Protection Officer and with specific Laser Safety Supervisors (LSS) within the School who are responsible for safe Schemes of Work and supervision in their specific areas. Terms of reference for and responsibilities of the School 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 School through his SLSO and LSS to ensure that the Local Rules are adhered to, and that all persons working with lasers in his School 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:
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 School 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:
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.
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:
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 School. 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.