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Laser Safety TrainingDepartment of Occupational Health &

SafetyRichard Grundsten, P.Eng.Laser Safety OfficerJune 2009

email: rgsten@yorku.ca

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Legislation

• The OHS Act requires employers to inform workers about the hazards of physical agents (e.g. laser radiation).

• American Standard for Safe Use of Lasers provides provides recommendations for safe use.

• Manufacturers must certify their lasers according to the ANSI standard.

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Contents of Laser Safety Program

• Laser Safety Training

• Inventory of Class 3b & 4 lasers

• Inspections of Class 3b & 4 lasers

• Personal Protective equipment

• Engineering controls

• Standard Operating Procedures

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Laser Classification

• Laser classification is based on the damaging effects of the laser beam on the eyes and skin.

• Non-beam hazards are not considered in the classification.

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Direct Intrabeam Viewing

Laser

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Specular Intrabeam Viewing

Laser E.g. Mirror

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Diffuse Reflected Viewing

Laser

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Class 1 Lasers (Exempt)

• Not capable of producing damaging radiation levels during normal operation.

• E.g. Laser printer, CD-Rom

• Does not apply to servicing.

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Class 2 & 3a Lasers (Low Power)

• Class 2 lasers emit visible light. Not hazardous if viewed less than 0.25 second. Maximum power is 1 mW for CW lasers. Eg. Barcode Scanner.

• Class 3a lasers probably not hazardous if viewed within 0.25 seconds. Hazardous if viewed with collecting optics. Maximum power is 5mW. Some require DANGER labels. E.g. Laser Pointer.

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Class 3b Lasers (Medium Power)

• Hazardous if viewed directly or by specular reflection. Diffuse reflection not usually hazardous. Upper limit is 0.5W for CW lasers.

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Class 4 lasers (high power)

• Lasers exceeding 0.5W • Hazardous under all viewing conditions: direct,

specular and diffuse.• Potential fire hazard when in contact with

combustible materials• Produce skin hazards from ultraviolet radiation.• Can produce laser generated air contaminants and

hazardous plasma radiation.

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Visible and Near-Infrared Radiation causes Retinal burn

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Mid and Far Infrared - causes damage to the cornea by increased temperature in tears and tissue water.

Mid Ultraviolet – causes photokeratitis (welders flash)

Mid

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Near Ultraviolet – Contributes to certain forms of cataracts

Xenon Chloride Excimer: Instant cataract, 308 nm pulsed laser

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Skin Hazards

• UV-A: Photosensitive reactions & tanning• UV-B & IR: Sun burn (1000 x sensitive than UV-A to burns)

• UV-C: Skin burn (sunburns without tanning, not from sun)

• Skin cancer and accelerated skin aging

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Skin Hazards

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Most Common Laser Accidents

1. Exposure during alignment -most frequent cause

2. Misaligned optics and stray beams

3. Improper methods of handling high voltage

4. Use of incorrect eyewear or eyewear failure

5. Improper restoration of equipment after service

6. Inhalation of laser generated materials

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Laser Accidents

• Nd:YAG 25.8%

• Argon 17.2%

• C02 11.9%

• Others 45.1%

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Type of Accidents

• Eye exposure -73%

• Skin exposure -13.9%

• Fire -7.3%

• Electrical Shock -3.6 (5 deaths)

• Note: Contact DOHS to arrange a course in CPR.

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Laser Eye Protection

• Required when engineering or administrative controls do not eliminate potential exposure.

• Must be enforced for Class 4 lasers.

• Should be enforced for Class 3b lasers.

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Eyewear Labeling

• Eyewear is labeled with the optical density at a specified wavelength.

• Many lasers radiate at than one wavelength thus one set of protective eyewear may not be appropriate.

• Indirect viewing maybe more appropriate when using lasers that are tunable over broad wavelength bands.

• In multi-laser environments colour coding or other identification methods of laser eyewear is recommended.

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Cleaning and Inspecting Laser Eyewear

• Laser eyewear must be cleaned and inspected regularly.

• Laser Eyewear in suspicious condition should be disposed of.

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Alignment Goggles

• Full protection goggles can make the beam invisible.

• Therefore users often perform alignments without protection.

• Alignment goggles let users view the beam safely. Users are protected by the blink response.

• Alignment goggles are only useful for visible lasers

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Enclosed Beam

• Enclosing the laser beam is the preferred control measure to class 3b or 4 lasers.

• This meets the requirements for a Class 1 laser and can be operated with no others controls.

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Limited open beam• A laser beam confined to a limited area greatly reduces the risk of

potential exposure. • In this case a detailed written standard operating procedure (SOP) is

sufficient.• The following list of measures should be used when total beam enclosure is not

possible: 1. Enclose the beam as much as possible, where access is not necessary.2. Use beam dumps, barriers, shields, blocks, baffles, etc. to block stray beams due

to reflections from mirrors, prisms, and other optical components.3. Use dark, absorbing, diffuse and fire-resistant materials for these purposes.

• Be aware that some surfaces can act like mirrors for C02 lasers even though they are black and visibly dull.

1. Ensure barriers used are able to withstand direct and diffusely scattered beams and do not support combustion or release toxic fumes when exposed laser beams.

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Totally Open Beam Path• Hazard analysis and Nominal Hazard Zone (NHZ)

assessment is required.

• The NHZ is the area in which the laser light is hazardous to the eye or skin.

• When optical layouts change often the re-evaluation of the NHZ can become tedious. Therefore it maybe easier to assume the entire laser laboratory area as the NHZ.

• In this situation all the requirements of a laser controlled area will apply to the laboratory.

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Without Protective HousingE.g. Servicing the Laser

• If the protective housing must be removed the following controls may be necessary:

• Eye protection

• Area controls

• Barrier, shrouds, beam stops, etc.

• Procedural controls

• Education and training

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Laser Controlled Area for Class 3b and 4 Lasers

When the beam path is not enclosed a laser controlled area must be established involving the following:

1. A warning sign must be posted at the entryway and, if necessary, within the laser controlled area.

2. Laser operated by trained personnel only.3. Beam path must be limited to the controlled

area.

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Controls recommended for Class 3b & required for Class 41. Direct supervision of an individual knowledgeable in

laser safety.2. Ensure that access by spectators is limited and requires

approval.3. Any potentially hazardous beam must be terminated in a

beam stop made of appropriate material.4. When possible use only diffusely reflecting materials in

or near the beam path. Avoid use of reflective materials near the beam paths. If such materials are present use of shields.

5. Personnel within the laser controlled area must be provided with the appropriate eye protection.

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Controls recommended for Class 3b & required for Class 4

(con’t)6. Ensure the laser beam is not at eye level of any

person working in the lab.

7. All windows or doorways inside a room must be covered to reduce the transmitted laser radiation to safe levels.

8. Laser must be stored or disabled (for example, removal of the key) laser when not in use. $1000 fine in USA if key left in a laser not being used.

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Controls Required for Class 4 Lasers

1. Ensure an accessible evacuation path exist in the event of an emergency.

2. Must have a “Panic Button” (switch or equivalent device) to quickly deactivate the laser or reduce the output to safe levels.

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Controls required for Class 4 lasers (Con’t)

3. Must use one of the following three options:(i) Non-Defeatable Controls. Interlocks that reduce

the output to safe levels when the door to the room is opened.

(ii) Defeatable Controls. If there is no laser hazard at the entryway and in cases where it is necessary to keep the laser operating such as with long term testing or surgery.

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Controls required for Class 4 lasers (Con’t)

(iii)Procedural Controls. When door interlocks are not feasible, the following procedural controls apply:

• A door, blocking barrier, screen, curtains, etc. must be used to block or attenuate the laser beam at the entryway to ensure that laser radiation outside the area does not exceed MPE, nor anyone gets exposed above the MPE immediately upon entry.

• A warning light or sound at the entryway indicating when the laser is energizing and operating. A lighted warning or flashing light are examples of this requirement.

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Other Beam Control Guidelines

• Secure mounts to table and optical components in their holders to prevent stray reflections from misaligned optics.

• Do not use flammable materials to trace beam paths or for stopping Class 4 laser beams.

• Use remote firing and monitoring of the beam where possible.

• For many applications it is possible to use relatively inexpensive digital (CCD) cameras.

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Other Beam Control Guidelines

• Use low power visible lasers for alignments of high powered visible and invisible lasers.

• Use beam shutters, filters or attenuators to reduce the beam power to safer levels whenever full beam power is not required.

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Standard Operating Procedures (SOPs)

• Written SOP for alignment procedures are recommended for Class 3b and required for Class 4 laser. For example the use of low power visible alignment lasers for path simulation of class 3b or 4 lasers or the wearing of alignment goggles.

• Protective equipment. When other control measures are inadequate to eliminate the possibility for hazardous eye or skin exposure, use of protective equipment may be required. Protective equipment generally means goggles or spectacles, barriers, windows, clothing and gloves and other devices specifically selected for protection against laser radiation.

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Warning Sign for Class 3b, 4 and Certain 3a Lasers

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Position 1 – Precautionary Statements

Laser Radiation–Avoid Eye and Skin Exposure to Direct and Scattered Radiation

Knock before Entering or

Do Not Enter When Light is On

Position 2 - Type of laser

Wavelength, pulsed duration (if appropriate) and maximum output power or energy

Position 3 - The Class of the laser

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Temporary Laser Controlled Area (E.g. Servicing Laser)

If a temporary laser controlled area is established, as in the case of servicing a laser a notice sign for temporary laser controlled area must be posted.

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Section 6

Non-beam Hazards

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Electrical Hazards

1. When possible have the laser connected by a qualified electrician and verify that the laser is properly grounded. Work in pairs while servicing the laser or if working after hours.

2. Request that at least one member of the group is trained in CPR. Be familiar with rescue procedures in case of an electrical shock.

3. Remove excessive wires/cables from the floor.

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Electrical Hazards (Con’t)

4. Do not wear rings and other metallic objects when working with electrical equipment.

5. Do not handle electrical equipment when hands, feet or body are wet, perspiring or when floor is wet. Stand on dry insulating rubber mat.

6. Lock-out and tag any electrical switch when servicing electrical equipment.

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Electrical Hazards (Con’t)

7. Components such as capacitors carry a lethal charge even after the main power has been disconnected.

8. These must be safely discharged by grounding (e.g. use a grounding strap).

9. When possible work with one hand to avoid becoming part of the circuit.

10. Review the manual to identify any components that have high voltage.

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Collateral and Plasma Radiation

• Measures must be taken to prevent exposure to collateral radiation such as X-rays generated by High Voltage (>15kV)

• Ultraviolet and visible radiation maybe generated during laser material interactions as well as from some laser discharge tubes and pumping lamps.

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Fire Hazards

1. Class 4 lasers represent a fire hazard. To reduce risk of fire, keep flammable materials away from open beams. If unprotected plastic tubing or wire insulation is present in vicinity of beam paths, it must be appropriately shielded using non-flammable materials to protect from potential exposure to the beam.

2. Fire extinguishers should be used for small fires only, if the fire can be put down safely with one extinguisher. Be familiar with the location of the extinguishers and the first aid kits. Report the fire to the University fire protection service.

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Chemical/Gas Cylinder Hazards

1. Compressed gases must be secured to a wall or other fixed object. Move cylinders with the cylinder carts and vent any toxic gases.

2. Laser dyes must be labeled and stored adequately. Fume hoods must be used for dye mixing. Use of containers for the circulator pumps is recommended.

3. Laser Generated Air Contaminants -Proper exhaust ventilation or respiratory protection must be used when lasers are used for material processing (cutting, marking, welding, etc.) or interaction with tissues.

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Other Non-beam Hazards

1. Explosion hazards (e.g. when heat is not dissipated quickly as with pulsed lasers)

2. Noise – Ear protection maybe required (if you have to raise your voice to be heard)

3. Ergonomics – Avoid tripping hazards, organize lab in order to move around safely.

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Quiz

• To complete the refresher training, complete the quiz http://www.yorku.ca/dohs/documents/Laser_Safety_Quiz.doc and send it to:

Richard GrundstenDepartment of Occupational Heath and SafetyEast Office Building, Room C37

• DOHS will inform you of the test results.