Laser Safety Program
University of Waterloo (UW)'s Laser Safety Program encompasses all work with class 3B and class 4 lasers under UWaterloo control. This program reflects the requirements in American National Standard for Safe Use of Lasers ANSI Z136.1-2007
The purpose of this program is to outline procedures and controls to ensure safe working conditions when working with or near lasers at the University of Waterloo.
The UW Laser Safety Program is provided to assist members of the University community to conform to the requirements of the Ontario Ministry of Labour, ANSI Z136.1- 2007 and related regulations and standards.
The Laser Safety Program applies to all persons: employees, students and visitors operating or working in proximity to class 3b or class 4 lasers. Persons included under this program are identified as laser workers. All components of the program are to be completed before a laser worker starts work.
- Program components
- Medical surveillance
- Laboratory safety committee
- Introduction to lasers
- Laser hazards
- Laser hazard control
- Laser facilities
- Laser safety video
- Supervisor information
- Laser safety training course
The Safety Office maintains an inventory of all class 3B and class 4 lasers
- Information will be provided by the Laser Supervisor
- The Safety Office will create a report indicating the nominal hazard zone and required OD for eye protection
Standard operating procedures
- Developed by the Laser Supervisor
- Copy kept on file with the Laser Safety Officer
- Online generic laser training
- Standard Operating Procedures (SOP) (Produced and updated by the Laser Supervisor)
- Laser Specific operating instructions (Laser Supervisor ensures worker is competent to operate laser)
A pre-employment examination will be done by a UW Occupational Health Nurse
Record of training
The record of training lists the components of the training and medical surveillance portions of the Laser Safety Program and is signed by the following individuals;
- Laser Safety Officer
- Laser Supervisor
- Occupational Health Nurse
Facilities housing lasers are requires to conform to ANSI Z136.1- 2007 to prevent unauthorized/accidental entry into the Nominal Hazard Zone of the laser
Personal protective equipment
All laser workers will be supplied with and required to use personal protective equipment listed in the SOP.
The following groups of individuals have specific responsibilities when working with lasers:
Laser Supervisors will be knowledgeable of education and training requirements for laser safety, the potential laser hazards and associated control measures for all lasers under the supervisor's authority. The supervisor will be familiar with general operating procedures of lasers under their control.
- Ensure that laser workers have been trained in the safe operation of the lasers or laser systems.
- Ensure that laser workers prior to operating or working in proximity to class 3b or class 4 lasers participate in the Laser Safety Program Training and complete the Laser Worker Registration form.
- Report known or suspected accidents to the Laser Safety Officer.
- Ensure that lasers under their control are not operated or modified without approval by the Laser Safety Officer.
- Ensure that all administrative and engineering controls are followed.
- Ensure that Standard Operating Procedures (SOP's) are written and available to Laser Workers under their supervision.
- Will participate in the Laser Safety Training Course.
- Will comply with regulations and standards prescribed by the Laser Safety Committee, Laser Safety Officer and the Laser Supervisor.
- Will be familiar with standard operation procedures (SOP's) and specific safety hazards of lasers which they are operating or working in proximity to.
- Will not operate a Class 3b or Class 4 laser unless authorized by the laser supervisor.
- Will report known or suspected accidents to their Laser Supervisor and the Laser Safety Officer.
- Will ensure that all spectators are properly informed of and protected from all potential laser hazards.
The Laser Safety Officer is directed by the Laser Safety Committee and will be knowledgeable in evaluation and control of laser hazards.
- Maintain inventory of all Class 3b and Class 4 lasers. Classify or verify classification if necessary.
- Be responsible for hazard evaluation of laser work areas, including the establishment of Nominal Hazard Zones.
- Approve standard operating procedures, alignment procedures and other control measures.
- Provide consultative services on evaluation and control of laser hazards and worker training programs.
- Inspect at least annually all class 3b and class 4 lasers for compliance with UW Laser Safety Program. Ensure any required corrective action is taken.
- Suspend, restrict or terminate the operation of a laser or laser system without adequate hazard controls, and advise Laser Safety Committee of such action.
- Approve wording on area signs and equipment labels.
- Maintain records required by various regulatory bodies. Ensure records are maintained of medical examinations and training has been provided.
- All persons working with class 3A and class 4 lasers are requires to successfully complete the Laser Safety Training Program (persons working under direct supervision such as undergraduate laboratories, demonstrations etc. are exempt).
- Complete the on-line Laser Safety Training Course (see "Online Laser Safety Training Course" - last menu item). On completion of the training course, the course number SO1066 "Laser safety training theory" will be placed in you personnel records at HR and can be viewed at myHRinfo.
- The Laboratory Supervisor is responsible for supplying practical training to the worker/student who is working with a laser under their supervision.
The practical training shall consists of:
- Laser operation as described in the manufacturers laser operation manual
- Specific hazards
- The written Standard Operation Procedures (S.O.P.)
- The practical training and eye exam information will be recorded a Record of Training form, this document signed by the worker, the supervisor and the Occupation Health Nurse to insure all requirements have been met.
The record of training will be produced when the online training has been completed. The worker is to print the page and
- Practical training completed and signed by Laboratory Supervisor and worker/student
- Eye exam completed and signed by Occupational Health Nurse
- The record is to be forwarded to the Laser Safety Officer. The record of training will be entered on your HR record as SO1067 "Laser safety practical".
Medical surveillance is limited to users of Class 3 B and class 4 lasers and will be conducted prior to beginning work with lasers.
The Occupational Health Nurse will conduct the initial eye exam. To make an appointment contact Linda Brogden at ext 36264.
The examination will consist of:
- Ocular history
- Visual acuity
- Macular function (Amsler grid)
- Color vision (Ishihara)
The worker/student may be referred to a specialist if deemed necessary.
Records will be maintained by the Occupational Health Nurse.
Upon completion of the ophthalmic exam the Occupational Health Nurse will complete the ophthalmic exam portion of the worker record of training form.
Terms of reference
The Laboratory Safety Committee's (LSC) overall responsibility is to monitor the use of radionuclides, biohazardous materials, chemicals, lasers, x-rays and other safety issues related to teaching and research laboratories*. The Committee is advisory to the Vice-President, University Research, and to the Safety Office and provides the following functions:
- Oversees strategies to ensure ongoing and adequate surveillance, hazard identification, and risk evaluation of laboratory related activities
- Assesses requirements for laboratory users training and laboratory safety procedures. Recommends revisions, when indicated
- Reviews reports related to laboratory safety services, activities, incidents, and interventions in laboratory areas. Recommends corrective actions, when indicated
- Maintains subcommittees based on areas of expertise to receive, review and approve reports and applications required by legislation and regulatory agencies
- Reports as required to the Vice-President, University Research
Membership of the Committee will include:
- Appointments by Vice-President, University Research, in consultation with faculty deans:
8 - Faculty members with the following areas of laboratory expertise appointed for renewable three-year terms:
- 2 - radionuclides (subcommittee required)
- 2 - biohazards (subcommittee required)
- 2 - chemicals
- 2 - lasers and x-rays
2 – Faculty Laboratory directors/managers - renewable three-year terms
Ex-officio members will include:
- Director, Health Services or designate
- Director, Office of Research Ethics or designate
- Director, Safety Office or designate
- Safety Officer, Safety Office
- Committee Chair is appointed by the Vice-President, University Research.
- Committee will meet at least annually and as required
- The Safety Office will provide secretarial services to the committee
A rudimentary understanding of laser light generation and how it differs from regular light is essential to working safely with lasers. This material is for reference only and is reviewed in the quiz.
This section will review aspects of:
The output of a laser may be described as continuous or pulsed.
Continuous wave (figure 5)
If energy is continuously pumped into the active medium, an equilibrium may be achieved between the number of atoms raised to a meta stable state and the number of photons emitted resulting in a continuous laser output. Output for continuous wave lasers is expressed as irradiance (E) which is the concentration of laser power incident on a given area or Power/Unit Area (W/cm2).
Pulsed lasers and Q-switched lasers (figure 6)
Pulsed laser emissions are produced when the excitation medium is modulated producing a pulse of laser radiation lasting usually less than 0.25 sec. Pulsed output may also be produced by blocking the beam with a rotating mirror or prism.
Q-switching or Q-spoiling is a technique employed to produce a very high output pulse. Q- switching is accomplished by using a device to prevent the reflection of photons back and forth in the active medium. This produces a higher population of electrons in the meta stable state. At a predetermined instant the Q-switch is turned off allowing the lasing action to continue producing very intense short pulses of laser radiation. Q-switched lasers produce pulses of 10 to 250 nanoseconds (ns).
Output for pulsed lasers (figure 6 - right) expressed as Radiant Exposure (H) which is the concentration of laser energy on a given area energy/unit area (J/cm2).
Examples of common laser types
|Laser type||Media||Wavelength (s)||Nanometers|
|Exclimer gas lasers||Argon Fluoride||(UV)||193 nm|
|Krypton Chloride||(UV)||222 nm|
|Krypton Fluoride||(UV)||248 nm|
|Xenon Chloride||(UV)||308 nm|
|Xenon Fluoride||(UV)||351 nm|
|Gas lasers||Nitrogen||(UV)||337 nm|
|Helium Cadmium||(UV)||325 nm|
|Helium Cadmium||(Violet)||441 nm|
|Helium Neon||(Green)||543 nm|
|Helium Neon||(Yellow)||594 nm|
|Helium Neon||(Orange)||612 nm|
|Helium Neon||(Red)||633 nm|
|Helium Neon||(NIR)||1,152 nm|
|Helium Neon||(MIR)||3,390 nm|
|Hydrogen Fluoride||(MIR)||2,700 nm|
|Carbon Dioxide||(FIR)||10,600 nm|
|Metal vapour lasers||Copper Vapour||(Green)||510 nm|
|Copper Vapour||(Yellow)||570 nm|
|Gold Vapour||(Red)||627 nm|
|Doubled Nd:YAG||(Green)||532 nm|
|Neodymium: YAG||(NIR)||1,064 nm|
|Erbium: Glass||(MIR)||1,540 nm|
|Erbium: YAG||(MIR)||2,940 nm|
|Holmium: YLF||(MIR)||2,060 nm|
|Holmium: YAG||(MIR)||2,100 nm|
|Chromium Sapphire (Ruby)||(Red)||694 nm|
|Titanium Sapphire||(NIR)||840-1,100 nm|
|Dye lasers||Rhodamine 6G||(VIS)||570-650 nm|
|Coumarin C30||(Green)||504 nm|
|Semiconductor lasers||Gallium Arsenide (GaAs)||(NIR)||840 nm|
|Gallium Aluminium Arsenide||(VIS/NIR)||670-830 nm|
Specular vs diffuse reflections
Specular reflections are mirror-like reflections and can reflect close to 100% of the incident light.
Flat surfaces will not change a fixed beam diameter only the direction (Figure 3).
Convex surfaces will cause beam spreading, conversely concave surfaces will make the beam converge (Figure 3).
Diffuse reflections (Figure 4) result when surface irregularities scatter light in all directions. The specular nature of a surface is dependent upon the wavelength of incident radiation. A specular surface is one that has a surface roughness less than the wavelength of the incident light. i.e. A very rough surface is not specular to visible light but might be to IR radiation of 10.6 um from a CO2 laser.
All lasers are classified by the manufacturer and labelled with the appropriate warning labels. Any modification of an existing laser or an unclassified laser must be classified by the Laser Safety Officer prior to use. The following criteria are used to classify lasers:
- Wavelength. If the laser is designed to emit multiple wavelengths the classification is based on the most hazardous wavelength.
- For continuous wave (CW) or repetitively pulsed lasers the average power output (Watts) and limiting exposure time inherent in the design are considered.
- For pulsed lasers the total energy per pulse (Joule), pulse duration, pulse repetition frequency and emergent beam radiant exposure are considered.
Class 1 lasers
Class 1 Lasers are lasers that are not hazardous for continuous viewing or are designed in such a way that prevent human access to laser radiation. These consist of low power lasers or higher power embedded lasers (i.e. laser printers).
Lasers previously classified as 2A lasers are now classified as class 1.
These lasers are exempt from all control measures:
Class 1M lasers
Class 1M lasers are ones that will not produce eye injury except when viewed with optical aids such as eye-loupes, telescopes, etc.
Class 2 visible lasers (400 to 700 nm)
Class 2 Visible lasers emit visible light which because of normal human aversion responses, do not normally present a hazard, but would if viewed directly for extended periods of time (like many other conventional light sources).
Class 2M lasers (400 to 700 nm)
Class 2 M lasers emit visible light which because of normal human aversion responses, do not normally present a hazard, but would be hazardous if viewed with optical aids.
Class 3 lasers
Direct viewing of the Class 3 Laser beam or viewing a specular reflection of the beam may damage the eye. Viewing diffuse reflections is not hazardous. The beams from these lasers are not a fire hazard.
Class 3R lasers
Class 3R laser are potentiality hazardous to the eye if the direct beam or specular reflection is viewed, to create a hazard the eye must be focused and stable (i.e. deliberately staring at the beam).
Class 3B lasers
Class 3B lasers are hazardous if the direct beam or specula reflection is viewed.
Class 4 lasers hazards include:
- Direct beam hazard the eye and skin
- Specular reflection hazard the eye and skin
- Diffuse reflection hazard the eye and skin
- Fire hazard
- May produce air borne contaminants
There are many different types of laser hazards. This section will describe them in detail. The following hazards will be described:
- Eye related effects
- Skin related effects
- Chemical hazards
- Explosion hazards
- Electrical hazards
These may include:
- Air borne contamination
- Collateral radiation
Structure of eye
The potential for injury to the different structures of the eye (Figure 5) depends upon which structure absorbs the energy and any repair processes that may exist for that structure.
The cornea serves two functions:
- Performs the initial focusing
- Protects various internal structures from the environment
The cornea is constantly exposed to the environment. For this reason it is constantly regenerated every 48 hours. Therefore, damage to this layer of the eye is usually repairable.
The lens is the main refractive tissue in the eye which focuses images on to the retina. Damage to the proteins that comprise the lens will result in cloudiness often referred to as a cataract. There is no repair mechanism for the lens, once it has been damaged it must be replace surgically.
The retina is the receptor organ for light focused on it by the lens. It consists of non-reparable specialized nerve tissue. Damage to parts of this tissue will result in permanent blindness or blind spots.
Wavelengths between 400 nm and 1400 nm are focused by the curved cornea and lens on to the retina. The optical gain is about 100,000-200,000 times. Viewing a laser beam or point source (Figure 6) will focus all the light on a very small area of the retina, resulting in a greatly increased power density and an increased chance of damage.
A large source of light such as a diffuse reflection of a laser beam produces light that enters the eye at a large angle is called an extended source. An extended source produces a relatively large image on the retina (Figure 7) and energy is not concentrated on a small area in the retina as in a point source.
Details of irradiation effects on eyes
Ultraviolet-B+C (100 - 315 nm)
The surface of the cornea absorbs all UV of these wavelengths (Figure 8) which produce a photokeratitis (weld flash) by a photochemical process which cause a denaturating of proteins in the cornea. This is a temporary condition because the corneal tissues regenerate very quickly.
Infrared-B and Infrared-C (1400 nm to 1.0mm)
Corneal tissue will absorb light with a wavelength longer than 1400 nm (Figure 8). Damage to the cornea results from the absorption of energy by tears and tissue water causing a temperature rise and subsequent denaturation of protein in the corneal surface.
Ultraviolet -A( 315 - 400 nm)
The lens absorbs Ultraviolet radiation of these wavelengths (Figure 9).
Photochemical processes denature proteins in the lens resulting in the formation of cataracts.
Visible light and Infrared-A (400 - 1400 nm)
The cornea, lens and vitreous fluid are transparent to light of these wavelengths but it is absorbed by retinal tissue (Figure 10).
Damage to the retinal tissue occurs by absorption of light and its conversion to heat by the melanin granules in the pigmented epithelium or by photochemical action to the photoreceptor. The focusing effects of the cornea and lens will increase the irradiance on the retina by up to 100,000 times. For visible light 400 to 700 nm the aversion reflex which takes 0.25 seconds may reduce exposure causing the subject to turn away from a bright light source. However this will not occur if the intensity of the laser is great enough to produce damage in less than 0.25 sec. or when light of 700 - 1400 nm (near infrared) is used as the human eye is insensitive to these wavelengths.
Laser radiation effects on skin
Skin effects are generally considered of secondary importance except for high power infrared lasers. However with the increased use of lasers emitting in the ultraviolet spectral region, skin effects have assumed greater importance.
Erythema (sunburn), skin cancer and accelerated skin aging are produced by emissions in the 200 to 280 nm range. Increased pigmentation results from exposure to light with wavelengths of 280 to 400 nm. Photosensitization has resulted from the skin being exposed to light from 310 to 700 nm. Lasers emitting radiation in the visible and infrared regions produce effects that vary from a mild reddening to blisters and charring.
These conditions are usually repairable or reversible however depigmentation, ulceration, and scarring of the skin, and damage to underlying organs may occur from extremely high powered lasers.
Summary of wavelengths of light and their effects on tissues
Below (Figure 11) is a summary of the interaction of optical radiation and various tissues. The wavelengths are divided into bands as defined by the International Commission on Illumination (CIE).
Many dyes used as lasing medium are toxic, carcinogenic, corrosive, or pose a fire hazard. All chemicals handled at the University of Waterloo must be accompanied by a material safety data sheet (MSDS) and all workers must have completed a workplace hazardous materials information system (WHMIS) course offered by the Safety Office. The MSDS will supply appropriate information pertaining to the toxicity, personal protective equipment and storage of chemicals.
Various gases are exhausted by lasers and produced by targets. Proper ventilation is required to reduce the exposure levels of the products or exhausts below standard exposure limits. For further information contact the Safety Office.
Cryogenic fluids are used in cooling systems of certain lasers. As these materials evaporate, they replace the oxygen in the air. Adequate ventilation must be ensured. Cryogenic fluids are potentially explosive when ice collects in valves or connectors that are not specifically designed for use with cryogenic fluids. Condensation of oxygen in liquid nitrogen presents a serious explosion hazard if the liquid oxygen comes in contact with any organic material. Although the quantities of liquid nitrogen that are used are small, protective clothing and face shields must be used to prevent freeze burns to the skin and eyes.
Compressed gases used in lasers present serious health and safety hazards. Problems may arise when working with unsecured cylinders, cylinders of hazardous materials not maintained in ventilated enclosures, and gases of different categories (toxins, corrosives, flammable, oxidizers) stored together.
Radiation other than that associated with the primary laser beam is called collateral radiation. Examples are X-rays, UV, plasma, radio frequency emissions.
X-rays could be produced from two main sources in the laser laboratories. One is high-voltage vacuum tubes of laser power supplies, such as rectifiers, thyratrons and crowbars and the other is electric-discharge lasers. Any power supplies which require more than 15 kilovolts (keV) may produce enough X-rays to cause a health hazard. Interaction between X-rays and human tissue may cause a serious disease such as leukaemia or other cancers, or permanent genetic effects which may show up in future generations.
UV and visible
UV and visible radiation may be generated by laser discharge tubes and pump lamps. The levels produced may exceed the Maximum Permissible Exposure (MPE) and thus cause skin and eye damage.
Interactions between very high power laser beams and target materials may in some instances produce plasmas. The plasma generated may contain hazardous UV emissions.
Radio frequency (RF)
Q switches and plasma tubes are RF excited components. Unshielded components may generate radio frequency fields which exceed federal guidelines.
Class 4 lasers represent a fire hazard. Depending on construction material beam enclosures, barriers, stops and wiring are all potentially flammable if exposed to high beam irradiance for more than a few seconds.
High pressure arc lamps, filament lamps, and capacitors may explode violently if they fail during operation. These components are to be enclosed in a housing which will withstand the maximum explosive force that may be produced. Laser targets and some optical components also may shatter if heat cannot be dissipated quickly enough. Consequently care must be used to provide adequate mechanical shielding when exposing brittle materials to high intensity lasers.
The most lethal hazard associated with lasers is the high voltage electrical systems required to power lasers. Several deaths have occurred when commonly accepted safety practices were not followed by persons working with high voltage sections of laser systems.
- Do not wear rings, watches or other metallic apparel when working with electrical equipment.
- Do not handle electrical equipment when hands or feet are wet or when standing on a wet floor.
- When working with high voltages, regard all floors as conductive and grounded.
- Be familiar with electrocution rescue procedures and emergency first aid.
- Prior to working on electrical equipment, de-energize the power source. Lock and tag the disconnect switch.
- Check that each capacitor is discharged, shorted and grounded prior to working in the area of the capacitors.
- Use shock preventing shields, power supply enclosures, and shielded leads in all experimental or temporary high-voltage circuits.
Control measures are devised to reduce the possibility of exposure of the eye or skin to hazardous levels of laser radiation. Substitution of engineering controls with administrative controls may be done with the approval of the Laser Safety Officer (LSO).
The control measures discussed in this section are adapted from ANSI Z136.1-2007, and they follow the basic premise of hazards evaluation and control. This section includes the following topics:
- Hazard evaluation
- Laser hazard controls
Hazard evaluation is done by the Laboratory Supervisor and the Laser Safety Officer.
Information about the laser and its application are gathered (Laser data form (PDF)) and from this data the nominal hazard zone is calculated.
Maximum permissible exposure (MPE)
The MPE is defined in ANSI Z-136.1 as "the level of laser radiation to which a person may be exposed without hazardous effect or adverse biological changes in the eye or skin." The MPE is not a distinct line between safe and hazardous exposures. Instead they are general maximum levels, to which various experts agree should be occupationally safe for repeated exposures. The biological effects of laser radiation are dependent on the wavelength of the laser and exposure duration. Therefore MPE's are calculated using correction factors for these indices. Calculations of MPE's are done by the Laser Safety Officer using ANSI Z-136.1 for each Class 3b and Class 4 laser.
Nominal hazard zone (NHZ)
In some applications open beams are required, making it necessary to define an area of potentially hazardous laser radiation. This area is called the nominal hazard zone (NHZ) which is defined as a space within which the level of direct, scattered or reflected laser radiation exceeds the MPE. The purpose of a NHZ is to define an area in which control measures are required. The Laser Safety Officer will determine the NHZ and the control measures to protect the laser worker from exposure to radiation above the MPE.
Control measures are devised to reduce the possibility of exposure of the eye or skin to hazardous levels of laser radiation. Substitution of engineering controls with administrative controls may be done with the approval of the Laser Safety Officer (LSO). The control measures below are adapted from ANSI Z136.1-2007
Although commercial laser products manufactured in compliance with the Federal Laser Product Performance Standard will be certified by the manufacturer and will incorporate some engineering controls, the use of the additional controls outlined in this section shall be considered in order to reduce the potential for hazard associated with some applications of lasers and laser systems.
|Engineering control measures||Reference Z136.1-2007||Laser classification|
|Without protective housing||(126.96.36.199)||LSO shall establish alternative controls|
|Interlocks on removable protective housings||(4.3.2)||X||X|
|Service access panel||(4.3.3)||X||X|
|Viewing windows, display screens and collecting optics||(188.8.131.52)||Assure viewing limited <MPE|
|Open beam path||(184.108.40.206)||
|Enclosed beam path||(220.127.116.11)||None is required if 4.3.1 and 4.3.2 fulfilled|
|Remote interlock connection||(4.3.7)||X|
|Beam stop or attenuator||(4.3.8)||X|
|Activation warning systems||(18.104.22.168)||X|
|Indoor laser controlled area||(22.214.171.124)||X|
|Class 3B indoor laser controlled area||X|
|Class 4 laser controlled area||(126.96.36.199||X|
|Outdoor control measure||(4.3.11)||X||O NHZ||X NHZ||O NHZ||X NHZ||X NHZ||X NHZ|
|Laser in navigable airspace||(188.8.131.52)||X||O NHZ||X NHZ||O NHZ||X NHZ||X NHZ||X NHZ|
|Equipment label||(4.3.14 and 4.7)||X||X||X||X||X||X||X|
|Laser area warning signs and activation warnings||(4.3.9)||X NHZ||X NHZ|
|Engineering control measures for enclosed class 3B & 4 lasers||Reference Z136.1 - 2007||Laser classification of enclosed class 3B & 4 laser|
|Interlocks on removable protective housings||(4.3.2)||X||X||X||X||X|
|Service access panel||(4.3.3)||X||X||X||X||X|
|Viewing windows, display screens and collecting optics||(184.108.40.206)||Assure viewing limited < MPE|
|Temporary laser controlled area if MPE exceeded||(4.3.12)||X||X||X||X||X|
O = applies when using optical aids
X = shall
NHZ = Nominal Hazard Zone analysis required
Description of engineering controls
A protective housing is a physical barrier preventing laser radiation in excess of the MPE from exiting the laser except through the aperture. It also functions as a barrier to associated non-beam hazards (electrical etc).
Laser use without protective housing
In some circumstances such as research and development and during the manufacture of lasers, operation of laser or laser systems without a protective housing may become necessary. In such cases the LSO shall determine the hazard and ensure that controls are instituted appropriate to the class of maximum accessible emission to ensure safe operation. These controls may include, but not be limited to:
- Access restriction
- Eye protection
- Area controls
- Barriers, shrouds, beams stops etc.
- Administrative and procedural controls
- Education and training
Interlocks on removable protective housing
Protective housings will have an interlock system which is activated when the protective housing is opened during operation and maintenance. The interlock prevents exposure to laser radiation above the MPE.
Service access panel
Service access panel which are portions of the protective housing and are intended to be removed only by service personnel, permit direct access to laser radiation. They must either:
- Be interlocked (fail-safe interlock not required)
- Or require a tool for removal and shall have an appropriate warning label
A master switch is a key or coded access (such as a computer code) required to operate the laser or laser system.
Viewing windows, display screens and collecting optics
All viewing portals and or display screens included as an integral part of a laser shall incorporate a suitable means (such as interlocks, filters, attenuators) to maintain the laser radiation at the viewing position at or below the applicable MPE for all conditions of operations and maintenance.
All collecting optics (such as lenses, telescopes, microscopes, endoscopes, etc.) intended for viewing use with a laser require a control (such as interlocks, filters, attenuators) to ensure the levels of laser radiation collected are below the MPE.
Control of the laser beam path shall be accomplished as described in the following sections.
Open beam path
The LSO will do a hazard assessment to determine the NHZ, personal protective equipment required and various non-beam hazards.
Enclosed beam path
The laser beam is enclosed and the laser exposure is less than the MPE.
Remote interlock connectors
The remote interlock connector reduces the accessible radiation below the MPE on entry to the area protected. This control is rarely used in research facilities
Beam stop or attenuators
The beam stop or attenuator is a device capable of preventing access to laser radiation in excess of the appropriate MPE level when the laser or laser system output is not required.
Activation warning systems
An alarm, a warning light or audible alarm used during activation or start-up of the laser.
Indoor laser control area
The LSO is required to do a hazard assessment to determine the NHZ, PPE and adequate control measures.
Remote firing and monitoring
Remote firing and monitoring console allows the laser to be operated from a remote location, removing the operator from the hazard.
Monitored and controlled during operation (no unattended operation).
Warning labels affixed to a conspicuous place on the laser housing or control panel.
Area warning signs and activation warning signs
A warning sign posted and and warning light indicating laser is on at the entrance of a room containing a laser.
A notice sign shall be posted outside a temporary laser controlled area.
Only signs provided or approved by the Safety Office will be posted.
Administrative and procedural controls are methods or instructions which specify rules, or work practices, or both, which implement or supplement engineering controls and which may specify the use of personal protective equipment.
|Control measure summary||Classification|
|Written standard operating procedures||O||X|
|Serviced by authorized personnel||X||X|
|Written alignment procedures||X||X||X||X|
|Skin protection if MPE for skin exceeded||X||X|
|Modification of laser||LSO will reclassify|
X - Shall O - Should *See following pages for details
Written SOP's are approved by the LSO and shall be maintained with the laser equipment for reference by the operator, and maintenance or service personnel.
All class 3b and class 4 lasers are to have written Standard Operating Procedures (SOP). SOP's are to be written under the supervision of the Laser Supervisor and approved by the Laser Safety Officer.
SOP's will contain the following information:
- Operating procedures
- Maintenance procedures
- Service procedures
- Alignment procedures
- The Nominal Hazard Zone (NHZ) for the above procedures as defined by the Laser Safety Officer
- Protective eyewear and other personal protective equipment as prescribed by the laser safety officer
Alignment of laser optical systems (mirrors, lenses, beam deflectors, etc.) shall be performed in such a manner that the primary beam, or a specular or diffuse reflection of a beam, does not expose the eye to a level above the applicable MPE. Procedures outlining alignment methods are to be approved by the LSO.
Output emission limitations
If, in the opinion of the LSO, excessive power or radiant energy is accessible during operation and maintenance, the LSO shall take such action as required to reduce the levels of accessible power or radiant energy to that which is commensurate with the required application.
Education and training shall be provided for operators, maintenance or service personnel.
Lasers shall be operated, maintained or serviced only by authorized personnel.
Eye protection is to be worn when engineering or other procedural and administrative controls are inadequate to eliminate potential exposure in excess of the application MPE.
Spectators shall not be permitted within a laser control area unless:
- Appropriate supervisory approval has been obtained
- The degree of hazard and avoidance procedure has been explained
- Appropriate protective measures are taken
Laser controlled area
The following items are required for the various types of laser control areas:
Class 3B laser controlled area
- Posted with the appropriate warning sign(s)
- Operated by qualified and authorized personnel
- Under the direct supervision of an individual knowledgeable in laser safety
- Located so that access to the area by spectators is limited
- Have any potentially hazardous beam terminated in a beam stop of an appropriate material
- Have only diffuse reflective materials in or near the beam path, where feasible
- Have personnel within the controlled area provided with the appropriate eye protection if there is any possibility of viewing the direct or reflected beams
- Have the laser secured such that the beam path is above or below eye level of a person in any standing or seated position, except as required for medical use.
- Have all windows, doorways, open portals, etc. from an indoor facility be either covered or restricted in such a manner as to reduce the transmitted laser radiation to levels at or below the appropriate ocular MPE
- Require storage or disabling (for example, removal of the key) of the laser or laser system when not in use to prevent unauthorized use.
Class 4 laser controlled area
Fulfill all items of Class 3b control areas and in addition incorporate the following.
- Personnel who enter a class 4 controlled area shall be adequately trained, provided with appropriate protective equipment, and follow all applicable administrative and procedural controls.
- Class 4 area/entryway safety controls shall be designed to allow both rapid egress by laser personnel at all times and admittance to the laser controlled area under emergency conditions.
- For emergency conditions there shall be a clearly marked "Panic button" (remote controlled connector or equivalent device) available for deactivating the laser or reducing the output to the appropriate MPE levels.
- Area or entryway safety controls to deactivate the laser or reduce the output to the appropriate MPE levels in the event of unexpected entry into the laser controlled area. These controls may be non-defeatable, defeatable or procedural as determined by the LSO using ANSI Z136.1.
Below (Figure 15) is an example of entryway controls for a Class 4 laser without entryway interlocks. The following features replace entryway interlocks. Entryway interlocks must be used if laser is run unattended.
- Activated by laser power switch
- Advice personnel not to enter when lit
- Sounds when door is opened
- Notifies personnel laser is operating
- Prevents persons entering directly into Nominal hazard Zone (NHZ) if a non-defeatable interlock was placed on the entryway the Laser Barrier and entry warning light may be omitted.
Temporary laser controlled area
Where removal of panels or protective housings, over-riding of protective housing interlocks, or entry into the NHZ becomes necessary (such as for service), and the accessible laser radiation exceeds the applicable MPE, a temporary laser controlled area shall be set up. This control area shall provide all safety requirements for all personnel, both within and without and a sign shall be posted outside the temporary laser controlled area to warn of the potential hazard.
Laser area signs
Laser area warning signs are available from the University of Waterloo Safety Office.
Class 3B sign Class 4 sign
The following is an account written by a researcher who sustained permanent eye damage viewing the reflected light of a Class 4 neodymium YAG laser emitting a 10-nanosecond pulse of 6 millijoule radiation at 1064 nanometers.
"When the beam struck my eye, I heard a distinct popping sound caused by a laser-induced explosion at the back of my eyeball. My vision was obscured almost immediately by streams of blood floating in the vitreous humour. It was like viewing the world through a round fish bowl full of glycerol into which a quart of blood and a handful of black pepper have been partially mixed." Dr. C.D. Decker.
The researcher had eye protection available but failed to wear it. Eye protection is required and its use enforced by the supervisor when engineering controls may fail to eliminate potential exposure in excess of the applicable MPE. Laser radiation is generated both by systems producing discrete wavelengths and by tunable laser systems producing a variety of wavelengths. For this reason it is impractical to select a single eye protection filter which will provide sufficient protection from all hazardous laser radiation. Therefore it is important to pick eye protection specific for the wavelength and power of the particular laser.
Laser protective eyewear requirements
- Laser protective eyewear is to be available and worn in by all personnel within the Nominal Hazard Zone (NHZ) of Class 3 b and Class 4 lasers where the exposures above the Maximum Permissible Exposure (MPE) can occur.
- The attenuation factor optical density) of the laser protective eyewear at each laser wavelength shall be specified by the Laser Safety Officer (LSO).
- All laser protective eyewear shall be clearly labelled with the optical density and the wavelength for which protection is afforded.
- Laser protective eyewear shall be inspected for damage prior to use.
The use of beam attenuators to align visible lasers will reduce laser beam intensities to a level that will allow the operator to align the beam without personal protective equipment.
Laser alignment cards for Ultraviolet and Infrared radiation allow operators to locate the beam during alignment procedures.
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Exposure or suspected exposure to laser radiation
- Seek medical attention immediately see UW first aid poster.
- After receiving medical attention, notify your supervisor as soon as possible.
- Notify the Laser Safety Officer
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