CONTENTS
Introduction
What is a laser?
How does a laser work?
Types of laser
Laser light
Laser hazards
Beam hazards
Non-beam hazards
Safety Standards
Laser Hazard Classification
Controlling laser hazards
Engineering Controls
Administrative/Procedural Controls
Personal Protective Equipment
College Procedures
Accident Reporting Procedures
Legislation

Appendix 1 - Laser Safety Standards
Appendix 2 - Legislation
Appendix 3 - Further Information

LASER SAFETY

Introduction
These notes are an introduction to laser safety. The contents include: what is a laser?; how does it work?; the different types of laser; laser light; laser hazards; safety standards; how to control laser hazards; personal protective equipment; College procedures; accident reporting procedures; and, legislation.

Please remember that these notes are only an introduction to laser safety, your supervisor will give further information, instruction and supervision.

What is a laser?
The word LASER is an acronym that stands for Light Amplification by Stimulated Emission of Radiation. Light energy is amplified to extremely high intensity by a process called stimulated emission. The energy generated by the laser is in or near the optical portion of the electromagnetic spectrum.

How does a laser work?
In most materials at room temperature, the majority of the electrons in the atoms are in unexcited energy levels or ‘ground’ states. By putting sufficient energy into the material it is possible to have more electrons in higher energy states than in the lower energy states - a ‘population inversion’. The electrons become excited by absorbing energy but cannot retain this energy for long and release it in the form of photons. These photons are very mobile and may collide with other excited electrons causing them to release an identical photon. This is called stimulated emission. The light energy is amplified by the photons colliding with other excited electrons causing them to simultaneously release yet more photons. Because of this they will always move in step or phase with one another, which is a further property of laser light - coherence. This amplification process continues only as long as there is a population inversion in the laser material. Therefore energy needs to be ‘pumped’ into the system to keep the process going. If the laser tube has mirrors placed at either end, the light can be made to travel backwards and forwards along the length of the tube and continue this process of stimulated emission. The front mirror of the laser is partially coated which allows a thin, parallel beam of laser radiation to be emitted from the laser tube. As long as the mirror reflects back enough photons to keep up the amplification process, the lasing action will continue.

Types of laser

Gas lasers - the active medium is a gas, usually excited into lasing by an electric current. Gas lasers include:
• helium-neon (He-Ne) - 633 nm (visible) and 1150 nm (infrared)
• argon (Ar) - 488 and 514 nm (visible)
• excimer - a mixture of gases such as krypton fluoride or xenon chloride
• carbon dioxide (CO2) - 10600 nm (infrared)

Dye lasers - the active medium is a liquid that can be made to lase when excited by a very intense flash of ordinary light or another laser. Using different dyes means that different wavelengths can be produced by tuning the laser optics. The laser dyes are typically very toxic and present many associated hazards.

Solid state lasers - the active medium is typically a rod of solid, transparent material such as ruby or emerald. They are excited into lasing by a brilliant flash of light from a flash-lamp. [One of the safety issues associated with the set up of a solid state laser is that it needs to be done at full power as the optical characteristics of the solid rod will vary depending upon output - from thermal effects.]
Solid state lasers include:
• neodymium-YAG (Nd:YAG) laser - 1064 nm (infrared) and 532 nm (visible) when frequency doubled (see below)

Semiconductor lasers - these are miniature lasers made from small pieces of semiconductor material. An electric current is applied directly to the material and it emits radiation from the junction between the semiconductor materials. The wavelength and out put depend upon the type of materials used. Diode lasers are commonly used in laser pointers and for surveying equipment. More powerful diode lasers are used to ‘pump’ solid state lasers such as Nd:YAG.

Chemical lasers - when some chemicals are mixed together they react violently, producing a great deal of heat. This can excite the atoms of the chemicals into lasing and so no external source of energy is needed. Hydrogen and fluorine react like this to produce hydrogen fluoride gas in an excited state and a laser beam that may be up to 200 W continuous wave output.

Laser light
The light emitted from a laser has these properties:
• it is monochromatic;
• it is very intense and of high power;
• it has low divergence (divergence is measured by the full angle of the spread of the beam, typically expressed in radians); and,
• it is coherent.

Coherence
This is a unique feature of laser radiation and broadly means that there is a relationship between the photons of the radiation, ie they are in phase. The photons from a light bulb are independent of each other, and are therefore called incoherent.

Speckle
One characteristic of laser radiation that is viewed when it has been scattered from some surfaces is laser speckle - which has a granular, grainy appearance. This effect is caused by the scattered laser radiation interfering with the incident laser radiation. The image seen by an observer has dark and bright elements where the coherent laser radiation has constructively and destructively interfered.

Wavelength
The colour of laser light is normally expressed in terms of the laser's wavelength in nanometres. Laser light is non-ionising and ranges from the ultra-violet region (100 - 400nm), through the visible region (400 - 700nm), and into the infrared region (700nm - 1mm).

Continuous or pulsed
Lasers can have different types of beam output. They may emit laser radiation in what appears to be a continuous steady beam known as a continuous wave, or CW laser. Alternatively the beam can be emitted as a pulse or a series of extremely short pulses of light in which case the lasers are referred to as pulsed lasers. In general it is not possible to operate pulsed lasers continuously, but it is possible to operate many CW lasers in pulsed output - this may be done to increase the output power of a laser (since the same energy is emitted over a shorter period).

Laser Hazards
Beam Hazards
The laser produces an intense, highly directional beam of light. If directed, reflected, or focused upon an object, laser light will be partially absorbed, raising the temperature of the surface and/or the interior of the object, potentially causing an alteration or deformation of the material. These properties, which have been applied to laser surgery and materials processing, can also cause tissue damage. Today, most high-power lasers are designed to minimise access to laser radiation during normal operation. Lower-power lasers may emit levels of laser light that are not a hazard.

The human body is vulnerable to the output of certain lasers and, under certain circumstances, exposure can result in damage to the eye and skin. The eye is almost always more vulnerable to injury than skin. The cornea (the clear, outer front surface of the eye's optics), unlike the skin, does not have an external layer of dead cells to protect it from the environment.

Retinal hazard region (400 - 1400 nm)

Of greatest concern is laser exposure in the retinal hazard region of the optical spectrum, approximately 400 nm (violet light) to 1400 nm (near-infrared) and including the entire visible portion of the optical spectrum. Radiation in this region is transmitted by the optical components of the eye and focussed upon the retina, where most of the radiation is absorbed in the retinal pigment epithelium and the choroid. This wavelength region is therefore referred to as the ‘retinal hazard region’ and permanent tissue damage can occur if the irradiance or radiant exposure is intense enough.
Two factors in laser-induced retinal damage are retinal irradiance and exposure duration, with pulsed lasers, pulse repetition rate is also a factor and so the exact type and extent of damage is difficult to predict. The location of the injury is also critical. The outlying parts of the retina are responsible for peripheral vision while the central area, called the macula, is used for fine central vision and colour vision. The very centre of the macula is called the fovea. This area has a very high concentration of cones which make it the only part of the retina capable of 20/20 vision. Damage in the region of the fovea will greatly impair vision, whereas some injuries ‘off-fovea’ may only produce relatively minor local ‘blind spots’, or retinal injuries only detectable by medical examination.

Within this region of the spectrum laser radiation is brought to focus on a very tiny spot on the retina. The light entering the eye from a collimated beam in the retinal hazard region is concentrated by a factor of 100,000 times when it strikes the retina. Therefore, a visible, 10 milliwatt/cm2 laser beam would result in a 1000 watt/cm2 exposure to the retina, which is more than enough power density (irradiance) to cause damage.

Ultraviolet Radiation (180 - 400 nm)
Shorter wavelengths of ultraviolet light (<315 nm) are primarily absorbed in the cornea resulting in inflammation of the corneal membranes, known as keratitis (in other cases this is commonly known as snow blindness or arc eye). The condition is painful, feeling like hot grit in the eye and accompanied by heavy tear flow and a marked aversion to bright light. Fortunately the eye usually recovers within 48 hours.

When UV-C (180 - 280 nm) and UV-B (280 - 315 nm) wavelengths are absorbed into the deeper layers of the cornea, a photochemical reaction may cause the cornea to turn milky. This reaction may occur six to twelve hours after exposure has taken place.

As a primary absorber of UV-A (315 - 400 nm) radiation, the lens is vulnerable to photochemical damage. Excessive, chronic exposure may lead to premature yellowing of the lens and cataract formation. Normally the retina is not significantly exposed to UV radiation because UV is absorbed by the cornea and lens. It should be noted however that, some people may have high sensitivity, and the use of antibiotics or other medications can be photosensitising.

Infrared radiation (780 nm - 1 mm)
The main biological effects of infrared radiation are infrared cataracts and flash burns to the cornea. Infrared absorption is mainly a thermal process and most injuries result from a temperature rise in the absorbing tissues.

As wavelengths increase into the IR-B and IR-C regions (above 1400 nm), the radiation is no longer transmitted to the retina, however absorption is very high. Above 2000 nm, radiation absorption can result in flash burns to the cornea (flash burns are injuries resulting from brief but intense heat exposures). If the infrared radiation is great enough to damage the cornea, the pain associated with it will be great enough to trigger the aversion response which may help to minimise the tissue damage.

Reflections
There are two principle types of laser reflections; specular and diffuse. In practice, the majority of reflections are a combination of the two.

Specular reflections occur from mirror-like surfaces. An incident beam striking a specularly reflecting surface such as a smooth, shiny surface will leave as a beam with properties to the incident beam - it will only change direction. If radiation is scattered into the eye as a specular reflection the full intensity of the beam could be received. Therefore, care should be exercised with unintentional reflections, such as from rings or watches.

Diffuse reflections are the type of reflections that occur from rough surfaces such as paper or matt-painted walls. The radiation scattered from the surface bears no relation to the direction of the incident radiation. The radiation is still seen by the eye however because a laser spot projected on a wall can generally be seen from any position within the room. Diffuse reflections normally present less of a hazard to the eye.

Non-Beam Hazards
In addition to the direct hazards to the eye and skin from the laser beam itself, it is also important to address other hazards associated with the use of lasers. These non-beam hazards, in some cases, can be life threatening, e.g. electrocution, fire, and asphyxiation.

Electrical hazards - most lasers make use of high voltages and pulsed lasers are especially dangerous because of the stored energy in the capacitor banks. Unless properly shielded, circuit components such as electronic tubes working at anode voltages greater than 5 kV may emit X-rays. In addition there are electrical hazards from associated equipment including trailing leads and plug-boards which are often left lying on the floor where people can trip over them or they can become flooded following a leakage of cooling water.

Fumes - including vaporized target material and reaction products from laser cutting, drilling and welding operations. These materials may well include, carbon monoxide, carbon dioxide, ozone, lead, other metals, and biological material.

Laser dyes - dye lasers normally use a lasing medium that comprises a fluorescent organic dye dissolved in an organic solvent. Examples included rhodamine in ethanol or ethylene glycol, and DCM (4-Dicyanomethylene-2-methyl-6-p-diethylaminostyryl-4-H-pyran) in ethanol. For most laser dyes, little or no toxicology information is available. Some of the dyes that have been tested have been shown to be mutagenic. Consequently, laser dyes should be treated as toxic unless toxicological evidence to the contrary exists. The solvent in which the dye is dissolved plays a major role in the hazards. In addition, practically all solvents used for dye solutions are flammable and toxic by inhalation and/or skin absorption. One of the solvents used, dimethyl sulfoxide (DMSO), is particularly hazardous as it has the unusual property of expediting the passage of materials through inert skin. In all cases an assessment of the risks to health should be made before commencing work with the dyes, in accordance with the Control of Substances Hazardous to Health Regulations 2002 (COSHH).

Optical - there may be a considerable hazard from the ultra-violet radiation associated with flash-lamps and CW laser discharge tubes, especially when ultra-violet transmitting tubing or mirrors (such as quartz) are used. The visible and near infra-red radiation emitted from flash tubes and pump sources and target re-radiation may be of sufficient radiance to produce potential hazard.

Safety Standards
There are two principle international laser safety standards:
• International Electrotechnical Commission (IEC) 60825 “Safety of Laser Products”
This document has been adopted by many countries around the world including the UK, France, Germany and Australia.
• American National Standards Institute (ANSI) Z136 Safe Use of Lasers

Further information on these standards is given in Appendix 1 - Laser Safety Standards.

Laser Hazard Classification
Exposure limits have been set for nearly all types of laser radiation. These limits are generally referred to as Maximum Permissible Exposures (MPEs). MPEs are those levels of laser radiation to which, in normal circumstances, persons may be exposed without suffering adverse effects. Detailed information on MPEs is given in the British Standard. Manufacturers of lasers and laser products are required to certify that the laser is designated as one of four general classes based on its MPE and label it accordingly. The following is a brief description of the primary categories of lasers (please note that the limits given are for visible light region and continuous wave lasers only - other limits apply to invisible and pulsed lasers - for details see British Standard):

Class 1 (< 7W visible)
Laser products that are normally safe under reasonably foreseeable conditions of use, either because of the inherently low emission of the laser itself, or because of its engineering design, such that it is totally enclosed and human access to higher levels of internal radiation is not possible during normal operation.

A Class 1 laser is considered “safe” under reasonably foreseeable conditions of operation and they present no hazards to the eye or skin. This class includes all lasers or laser systems which cannot emit levels of optical radiation above the exposure limits for the eye under any exposure conditions inherent in the design of the laser product. There may be a more hazardous laser embedded in the enclosure of a Class 1 product, but no harmful radiation can escape the enclosure.

Class 1M
Laser products that exceed the permitted accessible emission limits for Class 1 but which, because of the geometrical spread of the emitted radiation, cannot cause harmful levels of exposure to the unaided eye. However, the safe limit for ocular exposure can be exceeded, and injury can occur, if magnifying viewing instruments are used. Such instruments include binoculars and telescopes in the case of large-diameter collimated beams, or magnifying lenses and microscopes in the case of highly-divergent beams. Hazardous exposure can also occur if the spatial distribution of the emitted radiation (the beam diameter or divergence) is altered by the use of optical components or optical instruments.

Class 2 (< 1mW visible)
Laser products emitting low levels of visible radiation (that is at wavelengths between 400 and 700 nanometres) that are safe for the skin but which are not inherently safe for the eyes, but for which eye protection is normally afforded by natural aversion responses to bright light. Accidental exposure is therefore normally safe, although the natural aversion response can be overridden by deliberately staring into the beam, and can also be influenced by the use of alcohol or drugs.
A Class 2 laser or laser system must emit a visible laser beam. Because of its brightness, Class 2 laser light will be too dazzling to stare into for extended periods. Momentary viewing is not considered hazardous since the upper radiant power limit on this type of device is less than the MPE for momentary exposure of 0.25 second or less (the so-called “blink reflex”). Intentional extended viewing is considered hazardous.

Class 2M
Laser products that exceed the permitted accessible emission limits for Class 2 but for which, because of the geometrical spread of the emitted radiation, protection of the unaided eye is normally afforded by natural aversion responses to bright light. However, higher levels of ocular exposure can arise, and injury can occur, if magnifying viewing instruments are used. Such instruments include binoculars and telescopes in the case of large-diameter collimated beams, or magnifying lenses and microscopes in the case of highly-divergent beams. Hazardous exposure can also occur if the spatial distribution of the emitted radiation (the beam diameter of divergence) is altered by the use of optical components or optical instruments.

Class 3A (< 5mW visible (and < 25 w/m2))
A Class 3 A laser or laser system is safe for accidental viewing with the unaided eye (ie the “blink reflex” will provide protection). HOWEVER, direct intrabeam viewing of a Class 3A laser with an optical aid, eg binoculars, microscope, may be hazardous.

Class 3R
Laser products having a level of accessible emission up to five times the limits for Class 1 (if invisible) or Class 2 (if visible). The maximum permissible exposure may be exceeded but the risk of injury is low.

Class 3B (< 500mW visible)
Laser products having a level of accessible emission that can be harmful to the unaided eyes. If emission is outside the wavelength range 400 to 1400 nanometres these products can also be harmful to the skin.

Direct intra-beam viewing near this type of laser is always hazardous. Viewing diffuse reflections from a distance is normally safe provided the exposure duration is less than 10 seconds.

Class 4 (> 500mW visible)
Laser products having a level of accessible emission that can be harmful to both eyes and the skin. Diffuse reflections of the laser radiation may also be hazardous. The laser emission may also be sufficient to ignite materials on which it impinges, and to generate harmful radiation or fume hazards by interaction with target materials.

A Class 4 laser or laser system is any that exceeds the output limits (Accessible Emission Limits, AEL's) of a Class 3B device. As would be expected, these lasers may be either a fire or skin hazard or a diffuse reflection hazard. Very stringent control measures are required for a Class 4 laser or laser system.

Controlling Laser Hazards
Like any other potentially hazardous operation, lasers can be used safely through the use of suitable facilities, equipment, and well-trained personnel. The British Standard provides a detailed description of control measures that can be put into place to protect against potential accidents.

These control measures are divided into two distinctive categories, Engineering Controls and Administrative/Procedural Controls.

Engineering Controls are generally more costly to develop but are considered far more reliable by removing the dependence to follow rigorous procedures and the possibility of personal protective equipment failure or misuse. Engineering controls include all those safety features that are built into the design of the laser and its associated equipment. These are supplemented by the way in which the laser is used. For example when the laser and its associated optics are bolted down to an optical bench they cannot be accidentally knocked out of alignment. Examples of Engineering Controls include:
• key-control;
• remote interlock;
• protective housings;
• beam enclosures;
• protective filter installations;
• system interlocks.

Key control
Class 3B and Class 4 laser products not in use should be protected against unauthorised use by removal of the key control.

Remote interlock
The remote interlock connector of a Class 3B or Class 4 laser should be connected to an emergency master disconnect interlock or to room, door or fixture interlocks. The interlock should operate so as to prevent exposure to radiation in excess of the Accessible Emission Limit. This could be achieved by interlocking with the shutter of the laser system.

Administrative/Procedural Controls are designed to supplement Engineering Controls to ensure that laser personnel are fully protected from potential laser hazards. Administrative/Procedural Controls include:
• information, instruction and training;
• signage;
• standard operating procedures;
• arrangements for maintenance;
• arrangements for servicing.

Information, Instruction and Training
Operation of Class 3R, 3B and 4 laser systems can represent a hazard not only to the user but also to other people. Because of this hazard potential, only persons who have received information, instruction and training to an appropriate standard should be placed in control of such systems.

The initial College training - the Introduction to Laser Safety course - includes:
• awareness of the hazards arising from the use of lasers;
• effects of the laser upon the eye and the skin;
• the proper use of hazard control procedures, warning signs, etc;
• the use of personal protection; and
• accident reporting procedures.

Following the initial training the user should receive detailed instruction from their supervisor on:
• departmental arrangements; and, in particular,
• familiarization with the operating procedures of the laser system they will be using.

It is recommended that the supervisor closely oversees the activities of the new laser user and has a programme of activities that the user has to work through before they are authorised to use the laser independently.

Signage
All lasers should be labelled in accordance with BS EN 60825-1:1994. Lasers imported from the United States, where the lasers will have been labelled in accordance with ANSI Z136.1, should have additional labels classifying them in accordance with the British Standard. The following Table gives examples of the labelling that may be used.

Class 1
CLASS 1 LASER PRODUCT

Class 2 LASER RADIATION
DO NOT STARE INTO BEAM
CLASS 2 LASER PRODUCT
Class 2M LASER RADIATION
DO NOT STARE INTO BEAM OR VIEW
DIRECTLY WITH OPTICAL INSTRUMENTS
CLASS 2M LASER PRODUCT
Class 3B LASER RADIATION
AVOID EXPOSURE TO BEAM
CLASS 3B LASER PRODUCT
Class 4 LASER RADIATION
AVOID EYE OR SKIN EXPOSURE TO
DIRECT OR SCATTERED RADIATION
CLASS 4 LASER PRODUCT

Standard Operating Procedures
See section below - College Procedures.

Personal Protective Equipment
Personal Protective Equipment should only be used when the above measures do not provide sufficient control. Personal Protective Equipment includes:
• protective eyewear
• protective clothing

Protective eyewear
Protective eyewear should be comfortable to wear, provide as wide a field of view as possible, maintain a close fit while still providing adequate ventilation to avoid problems in misting up, and provide adequate visual transmittance. Care should be taken to avoid, as far as is possible, the use of flat reflecting surfaces that might cause hazardous specular reflections. It is important that the frame and any sidepieces should give equivalent protection to that provided by the lenses.

The following should be considered when selecting suitable protective eyewear:
a) wavelength(s) of operation;
b) radiant exposure or irradiance;
c) maximum permissible exposure (MPE);
d) optical density of eyewear at laser output wavelength;
e) visible light transmission requirements;
f) radiant exposure or irradiance at which damage to eyewear occurs;
g) need for prescription glasses;
h) comfort and ventilation;
i) degradation or modification of absorbing media, even if temporary or transient;
j) strength of materials (resistance to shock); and,
k) peripheral vision requirements.

Protective clothing
Where personnel may be exposed to levels of radiation that exceed the Maximum Permissible Exposure for the skin, suitable clothing should be provided. Class 4 lasers especially are a potential fire hazard and protective clothing worn should be made from a suitable flame and heat resisting material.

College Procedures
High Power Laser Safety Policy and Code of Practice
The College has a policy concerning the use of high power laser systems. The policy requires all work with Class 3B and Class 4 lasers by staff and students, on or off College premises to be subject to protocols approved by Heads of Departments and to comply with BS EN 60825 -1994 “Radiation safety of laser products, equipment classification, requirements and user’s guide”.

There is a supporting Code of Practice which describes the College’s requirements on the use of Class 3B and Class 4 lasers. Laser use includes use of lasers for:
1. research;
2. teaching, instruction and demonstration;
3. design, manufacture, alteration and installation maintenance or modification;
4. entertainment or display; and,
5. any College activity on external sites.

NOTE: Class 1 lasers, such as laser printers and compact disc readers in normal use are generally exempt from any requirements. Safe working with Class 1M, Class 2 or 2M, or Class 3R lasers should be covered by general departmental guidance.

This Code of Practice covers the specific arrangements to be made by departments to ensure safe working with Class 3B and Class 4 lasers and includes provision for:
1. protocols to be approved before work starts;
2. the registration of areas, work and users;
3. the need for the lowest class of laser to be used in all circumstances;
4. no use without prior notification or by unregistered users; and,
5. the work not to present risks to persons or environments.
The current version of the High Power Laser Policy and Code of Practice can be found on the College’ Safety Unit website at: http://www.ad.ic.ac.uk/safety/policies/lasers.htm.

Protocols
Protocols should be developed and implemented before any use of Class 3B and Class 4 lasers commences. The protocols should be developed within the framework of a department’s laser safety rules. If there is a significant change in an activity or in the known hazard of the use of the laser the protocol should be reviewed.

Protocols should describe:
1. the use of the laser;
2. the Designated Area being used and the identification of enclosures including signage and warning systems for entrances and restriction of access;
3. the laser(s) being used, their labelling and testing, calibration, maintenance and safety testing, including the suitability of the measuring equipment and the competence of those who use it;
4. the training and competence of the user(s);
5. the use of personal protective equipment;
6. any departures from standard conditions.

Designated Areas
Designated Areas where Class 3B and Class 4 lasers are used must be registered with the College Safety Unit. The sign (shown right) must be affixed near to the entrance of each Designated Area and contain the details of the Laser Safety Officer for the Area and the names of two persons who may be contacted in the event of an emergency.

Laser Registration Form
All Class 3B and Class 4 lasers must be registered with the College Safety Unit via the Departmental Laser Safety Officer.

Laser User Form
All laser users must be registered with the College Safety Unit via the Departmental Laser Safety Officer.

Eye examination
The British Standard states that “pre, interim, and post employment ophthalmic examinations of workers using Class 3B and Class 4 lasers have value for medical legal reasons only and are not a necessary part of a safety programme.”

A medical examination by a qualified specialist should be carried out immediately after an apparent or suspected injurious ocular exposure. Such an examination should be supplemented with a full biophysical investigation of the circumstances under which the accident occurred.

Laser Safety Officer
The British Standard specifies that any facility using Class 3B or Class 4 lasers or laser systems should designate a Laser Safety Officer to oversee safety for all operational, maintenance, and servicing situations. This person should have the authority and responsibility to monitor and enforce the control of laser hazards. This person is also responsible for the evaluation of laser hazards and the establishment of appropriate control measures.

The College Laser Safety Officer monitors departmental arrangements and assists departments by:
1. advising or arranging for the provision of expert advice;
2. approving the competence of Departmental Laser Safety Officers prior to their appointment;
3. reviewing protocols prior to their approval by the Head of Department;
4. maintaining central registers of Designated Areas, users and laser equipment - based on information provided by departments;
5. the provision or arrangement of training courses and advising on training needs; and
6. providing specialist input to investigating the causes and the consequences of accidents and incidents involving lasers and their use.

Departmental Laser Safety Supervisor
All departments that use Class 3B or Class 4 lasers are required, by the College High Power Laser Policy, to appoint a Departmental Laser Safety Officer.

Accident Reporting Procedures
All incidents or accidents involving the use of lasers must be reported to the Safety Unit as soon as possible. The Departmental Laser Safety Officer should investigate the accident and ensure that any individuals who may have been exposed to damaging laser radiation are referred for assessment of any damage, preferably within 24 hours of the suspected exposure. The Occupational Health service will assess individuals referred to them for damage to eyes or skin following possible exposure to laser radiation.

Certain accidents may be reportable to the Health and Safety Executive under the Reporting of Injuries Diseases and Dangerous Occurrences Regulations 1995. These include:
• an accident involving a “member of the public” (which includes undergraduate and postgraduate students) which requires them to be taken from the scene of the accident to hospital for treatment;
• an accident to someone at work which prevents them from being able to do their normal work for more than three days; and,
• an accident which causes someone to suffer a “specified major injury”. Specified major injuries include: loss of sight (whether temporary or permanent); and, any injury requiring admittance to hospital for more than 24 hours.

Legislation
There is no specific legislation in the UK regarding the use of lasers. In common with all other work activities the employer is required to ensure compliance with the Health and Safety at Work etc Act 1974. The Management of Health and Safety at Work Regulations 1999 require employers to carry out Risk Assessment; and the Provision and Use of Work Equipment Regulations 1998 require the employer to ensure that work equipment is suitable for its intended purpose and that users are adequately trained. Further details on health and safety legislation are given in Appendix 2.

APPENDIX 1 LASER SAFETY STANDARDS

Safety Standards
There are two principle international laser safety standards:
• International Electrotechnical Commission (IEC) 60825 “Safety of Laser Products”
This document has been adopted by many countries around the world including the UK, France, Germany and Australia.
• American National Standards Institute (ANSI) Z136 Safe Use of Lasers

British Standard

The International Standard, IEC 60825-1, has been adopted by the British Standards Institute and has been published in the UK as BS EN 60825-1:1994 “Safety of laser products. Part 1. Equipment classification, requirements and user’s guide”.

The standard is divided into three sections (General; Manufacturing Requirements; and, User’s Guide) with six Annexes (examples of calculations; medical considerations; bibliography; summary tables; high-power laser considerations; and related standards).

The objectives of the Standard are stated as:
1. to protect persons from laser radiation in the wavelength range 180 nm to 1 mm by indicating safe working levels of laser radiation and introducing a system of classification of lasers and laser products according to their degree of hazard.
2. to lay down requirements for both the user and the manufacturer to establish procedures and supply information so that proper precautions can be adopted.
3. to ensure adequate warning to individuals of hazards associated with accessible radiation from laser products through, labels and instructions.
4. to reduce the possibility of injury by minimising unnecessary accessible radiation and to give improved control of the laser radiation through protective features and provide safe usage of laser products by specifying user control measures.
5. to protect persons against other hazards resulting from the operation and use of the laser products.

British Standard BS IEC TR 60825-5:1998 is a checklist for manufacturers to ensure compliance with IEC 60825-1

American Standard
The American Standard consists of three published standards and there are others in various stages of draft. The main standard ANSI Z136.1 (originally published in 1973, latest revision 2000) includes the basis of laser hazard assessment including the Nominal Hazard Zone (NHZ) concept and measurements, establishes Maximum Permissible Exposure (MPE) limits based on bioeffects of the eye and skin, introduces a general classification scheme, specifies the recommended control measures, outlines suggested medical surveillance practice, specifies training requirements and recommends practices for other (non-beam) concerns.

In addition to the Z136.1 standard the two other published American Standards are:
• ANSI Z136.2 (1997) Safe Use Of Optical Fiber Communication Systems Utilizing Laser Diode And LED Sources, and
• ANSI Z136.3 (1996) Safe Use Of Lasers In Health Care Facilities.

The standards in draft, include:
• ANSI Z136.5 Safe Use of Lasers in Educational Institutions
This standard will take the requirements of ANSI Z136.1 and apply them to the unique environments associated with educational institutions. It is intended for university, college, secondary, and primary educational environments, and also for educational researchers and students who use lasers as part of their academic instruction and development.
ANSI Z136.6 Safe Use of Lasers Outdoors

APPENDIX 2 LEGISLATION

Health and Safety at Work etc Act 1974
The Health and Safety at Work etc Act 1974 (the Act) is the primary legislation governing health, safety and welfare at work.

Section 2 of the Act makes it the duty of every employer to ensure, so far as is reasonably practicable, the health, safety and welfare at work of all his employees. This includes: provision and maintenance of plant and systems of work that are safe and without risk; and information, instruction and training.

Section 3 extends this duty so that employers must also ensure, so far as is reasonably practicable, the health and safety of non-employees affected by the work activities.

Section 7 makes it the duty of every employee while at work to take reasonable care for their own health and safety and of other persons who may be affected by their acts or omissions at work. Employees are also required to co-operate with their employer as regards any duty or requirement imposed by health and safety legislation.

Section 8 makes it the duty of everyone not to interfere with, or misuse, anything provided in the interests of health, safety or welfare.

Section 9 states that no employer can charge an employee for anything done or provided in accordance with health and safety legislation.

The Act and its associated Regulations are enforced by Inspectors from the Health and Safety Executive. Inspectors have powers of entry and can take photographs, seize items, take samples, and take witness statements. Inspectors can also serve Improvement and Prohibition Notices and can prosecute companies and individuals.

Management of Health and Safety at Work Regulations 1999
These regulations are aimed at improving health and safety management and emphasise the need to develop a safety culture where the management of health and safety is fully integrated within the organisation.
Employer’s key duties
Employers are required to: assess the risk to health and safety of employees and to anyone else who may be affected by the work activity; make arrangements for putting into practice the preventive and protective measures that follow from the risk assessment; appoint competent persons to provide health and safety assistance; and, co-operate and co-ordinate with other employers where they share premises or workplaces.
Employees' key duties
Employees are required to: make full and proper use of any arrangements established by the employer for health and safety at work; and, report to the employer details of any work situation which might represent a serious or imminent danger.
Main requirements of the regulations
Risk assessments should be carried out to identify hazards and evaluate the risks arising from them in order to establish the necessary control measures to ensure health and safety. In assessing the risks consideration should be given to all those who may be affected, including visitors and contractors. The significant findings of the assessment should be recorded. In deciding upon the measures to be taken, wherever possible the risk should be avoided altogether. Where this is not possible, the risk should be dealt with at source, prioritising measures that protect the whole workforce. Assessments should be revised if changes take place that suggest they are no longer valid. Control measures should be regularly reviewed for effectiveness as part of good health and safety management.
Competent persons should be appointed to provide health and safety assistance. These may be in-house, external or both. They must have adequate time and resources to carry out their functions. The appointment of competent persons does not remove employers' legal responsibilities.
Emergency procedures should be established. An emergency plan should be drawn up in consultation with appropriate bodies, eg the emergency services, on-site security personnel. As a minimum, it should cover fire and loss of electrical power.

All employers need to co-ordinate their activities to ensure that temporary workers whether on fixed or short-term contracts are provided with essential information concerning the workplace and in particular any risks to their health and safety. Employers must also ensure that basic induction training is given and following changes of duties, equipment, work processes etc. Training should include emergency procedures, reporting procedures, risks in the work and the precautions needed. Training will need to be repeated periodically to ensure continued competence. Health and safety information should be provided to contractors' staff where necessary.

Provision and Use of Work Equipment Regulations 1998
These regulations are aimed at safeguarding the health and safety of employees from hazards arising from the provision and use of work equipment. They contain general requirements covering all hazards and specific minimum requirements on selected hazards. Further requirements may be imposed by more specific regulations, for example the Electricity at Work Regulations and the Control of Substance Hazardous to Health Regulations.
Employer’s key duties
The employer must ensure that: work equipment is suitable for the purpose for which it is provided, and is properly maintained; information, instruction and training is given in the safe use and maintenance of equipment and what to do if things go wrong; there is suitable guarding for mechanical hazards; there is protection against rupture or disintegration; there is protection against burns and scalds from hot or cold equipment or its products; there are control devices which are visible, identifiable, marked and located outside danger zones and that control systems are safe; work equipment is stabilised, by clamping or other means, and that sufficient lighting is provided when the work equipment is used; where there are health and safety hazards, work equipment is marked clearly and incorporates warnings.

Personal Protective Equipment Regulations 1992
These regulations cover equipment and clothing worn or held by people at work to protect them against risks to their health and safety. They set out requirements for assessing, selecting, providing, maintaining and using personal protective equipment (PPE). PPE should always be regarded as a last resort. Steps should first be taken to prevent or control risk at source by making machinery or processes safer and by using engineering controls and safe systems of work.
Employers' key duties
Employers are required to: assess risks to health and safety which have not been avoided by means other than PPE, to determine whether PPE provided and proposed is 'suitable'; provide suitable PPE, free of charge, to protect employees against risks that have not been controlled by other means; take all reasonable steps to ensure that PPE is properly used; maintain PPE in clean and efficient working order, replace it as necessary and provide appropriate storage for PPE when it is not in use; and, provide employees with comprehensible information, instruction and training to enable them to make efficient use of PPE.
Employees' key duties
Employees are required to: make full and proper use of PPE provided and report any loss or obvious defect in PPE to their employer.
General comments
Due to the nature of certain types of laser work some form of protective clothing may be required. The types of protective clothing needed will depend on the types of hazard and levels of risk and will differ from one laser facility to another but may include eye protection and respiratory protective equipment. 'Suitable' PPE is: appropriate for the risk; takes account of ergonomics and the health of wearers; fits the wearer correctly; effectively controls identified risks without increasing risks elsewhere; and, is compatible with any other types of PPE which needs to be worn for a particular activity.

Control of Substances Hazardous to Health Regulations 2002
These regulations provide a legal framework to help protect people in the workplace against health risks from hazardous substances. They require employers to assess the risks to health when work is liable to expose anybody to a substance hazardous to health. Employers must also comply with the other requirements of the Regulations as regards preventing or controlling exposure; examining, testing and maintaining the control measures; monitoring exposure; providing health surveillance; and information, instruction and training.
Main requirements of the regulations
The risk assessment needs to consider what substances are hazardous to health; how are they hazardous; and, what measures are required to prevent or control exposure. The assessment, which needs to be recorded and readily available, will be regarded as suitable and sufficient if the detail and expertise with which it is carried out are commensurate with the nature and degree of risk arising from the work, as well as the complexity and variability of the process.
In the Regulations a substance hazardous to health is defined as: a carcinogen; a substance listed in Chemicals (Hazard Information and Packaging for Supply) Regulations 1994 (CHIP) as very toxic, toxic, harmful, corrosive or irritant; a substance with a Maximum Exposure Limit (MEL) or Occupational Exposure Standard (OES); a biological agent; dust of any kind when present at a substantial concentration in the air; any other substance which creates a comparable hazard to health to any of the above.
Substances can be hazardous to health through: inhalation; ingestion; absorption through the skin or eyes; or, injection; and can cause: acute or chronic illness (including cancer); disease; sensitisation; or, allergic reaction.
The best method of control is to eliminate the hazardous substance or replace it with one that is less hazardous. If this cannot be achieved then engineering controls, administrative controls, or personal protective equipment (PPE) must be used to reduce the risk. The use of PPE is only a permissible approach if it is not reasonably practicable to achieve adequate control by other means alone or in combination. Sometimes adequate control can only be achieved through a combination of all or some of these methods. Engineering controls include: total enclosure (glove box); partial enclosure (fume cupboard); Local Exhaust Ventilation; and, general ventilation. Control measures need to be checked regularly to ensure they are being properly used, and they need to be maintained in an efficient state, in effective working order and in good repair. One of the most important administrative controls is Good Laboratory Practice based upon: no eating, drinking, smoking, chewing, application of cosmetics, taking of medication; wearing suitable protective clothing; good personal hygiene; clearing up spillages promptly; and, knowing the appropriate emergency procedures.
The risk assessment needs to cover emergency procedures including: the means for dealing with leaks, spills or uncontrolled releases; safe disposal of substances and contaminated materials; and the provision of sufficient suitable personal protective equipment.
Atmospheric sampling may be required to: monitor failure of control measures; ensure a Maximum Exposure Limit is not exceeded; and, check on control measures.
Health surveillance may be required to: protect the health of individuals by detection of adverse effects at early stages; evaluate the effectiveness of control measures; detect and evaluate hazards to health; and, assess immunological status.
Information, Instruction, and Training are needed on: the nature and degree of risks to health; how to use control measures; the reasons for personal protective equipment; monitoring procedures; the role of health surveillance; and, emergency procedures.

Electricity at Work Regulations 1989
These regulations require precautions to be taken against the risk of death or personal injury from the use of electricity in work activities.
Regulation 6 of the Electricity at Work Regulations requires that electrical equipment which may be exposed to adverse conditions should be of such construction or so protected as to prevent the danger that may arise from such exposure.
The arrangements for inspection and testing of electrical equipment by a competent person should include reliable defect reporting and record keeping systems. Maintenance or repair should only be undertaken by a competent person.

Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995
The Reporting of Injuries, Diseases and Dangerous Occurrences Regulations 1995 (RIDDOR) require certain injuries, dangerous occurrences and diseases arising out of or in connection with work to be notified to the enforcing authority. Fatal and major injuries to employees, students or other non-employees should be reported immediately by telephone and confirmed in writing. Other injuries to employees which involve an absence from work or incapacity for normal work for more than three days should be reported within ten days. Reportable major injuries include acute illness requiring medical treatment which has resulted from exposure to a biological agent or its toxins or infected material.
Cases of occupational ill health arising from work are also reportable.
Although not specifically required by RIDDOR, details of all, even minor, injuries at work and near misses should be recorded, with details of the immediate cause of the injury and of the action taken.

Health and Safety (Safety Signs and Signals) Regulations 1996
These regulations require employers to provide specific safety signs when ever there is a risk that has not been avoided or controlled by other means, eg by engineering controls and safe systems of work. The safety signs used need to comply with the requirements of British Standard BS 5378 Safety signs and colours; this includes the use of standard pictograms, supplemented by wording as appropriate; and following the colour scheme of:
• red for prohibition - eg No unauthorised entry;
• blue for mandatory - eg wear protective eyewear;
• yellow for caution - eg laser hazard; and,
• green for safe condition - eg first-aid box.
Employers are required to maintain the signs they provide and to explain unfamiliar signs to their employees and tell them what to do when they see a safety sign.

APPENDIX 3 FURTHER INFORMATION

1) Laser Institute of America

The Laser Institute of America (LIA) is the professional membership society dedicated to fostering lasers, laser applications and safety world-wide. Serving the industrial, medical, research and military communities, LIA offers technical information and networking opportunities to laser users from around the globe. The website address is: http://www.laserinstitute.org.

LIA offers a wide array of products and services including reference guides, video tapes, a hazard evaluator software, warning signs and labels, safety courses, and conferences such as the International Laser Safety Conference. Institute members receive the Journal of Laser Applications.