Laser Safety

1. Laser Safety

2. Introduction • Lasers are high-energy focused electromagnetic radiation that, if misused or abused, can cause serious injuries or blindness. • The materials in this program are designed to provide an overview of Lasers, their potential health effects, and how to protect yourself.

3. Objectives • Laser classifications • Class III safety rules • Class IV safety rules • How can I recognize laser hazards in the workplace? • What are some examples of possible solutions for workplace hazards?

4. LASER • L ight • A mplification • S timulated • E mission • R adiation

5. Laser Basics • Lasers differ from ordinary light in 3 ways: • Monochromatic • Directional • Coherent • Lasers can be more hazardous than ordinary light because their energy is concentrated on a very small area.

6. Laser Basics • Laser components

7. Laser Basics • Laser Design • Lasing Medium • Gas • Liquid • Solid • Semiconductor • Dye • Excitation Mechanism • Power Supply • Flashlamp • Laser

8. Laser Basics • Laser Design (cont’d) • Feedback Mechanism • Mirrors • Output Coupler • Semi-Transparent Mirror

9. Laser Basics • Types of Lasers • Continuous Wave (CW) • Pulsed • Q-Switched

10. Laser Radiation • Lasers emit focused light radiation • Infrared (780-nm – 1-mm) • Far-IR (IR-B, IR-C) (1400-nm – 1-mm) • Near-IR (IR-A) (780-nm – 1400-nm) • Visible (400-nm – 780-nm) • Ultraviolet (200-nm – 400-nm) • Far-UV (UV-B, UV-C) (200-nm – 316-nm) • Near-UV (UV-A) (315-nm – 400-nm)

11. Laser Hazards • Bioeffects – Damage to living organisms/tissues • Primary damage sites • Eyes • Skin • Lasers can damage • Thermally • Acoustically • Photochemically

12. Laser Hazards • Skin (Dermal) Damage • Dermis • IR-A • Epidermis • UV-B, UV-C

13. Laser Hazards • Eye Damage • Retina • IR-A, Visible Light • Lens • UV-A • Cornea • UV-B, UV-C, IR-B, IR-C

14. Laser Hazards – Eye Damage Retina subject to damage from intense visible light and IR-A Human Eye

15. Laser Hazards – Eye Damage Lens subject to damage from UV-A Human Eye

16. Laser Hazards – Eye Damage Cornea subject to damage from UV-B, UV-C, IR-B, and IR-C Human Eye

17. Laser Hazards - Exposure Limits • Maximum Permissible Exposure (MPE) • The highest level of laser energy to which the eye or skin can be exposed for a given laser without suffering significant adverse effects • Nominal Hazard Zone (NHZ) • Area within which the MPE could be equaled or exceeded. • Nominal Ocular Hazard Distance (NOHD) • Distance from the laser source along the axis of the beam beyond which eye exposures should cause no significant adverse effects

18. Laser Hazards - Electrical • Most common non-beam related hazard • Power supplies and capacitors can possess high voltage • Employ proper lockout/tagout procedures when working with lasers

19. Laser Hazards - Chemical • Many organic dyes used in certain lasers can be hazardous • Can be mutagenic, carcinogenic, toxic, and/or reactive • Depending upon the target, many lasers can cause the release of toxic decomposition products • Employ proper chemical safety procedures, including proper ventilation, containment, respiratory protection, and personal protective equipment, as needed to control the hazard.

20. Laser Hazards - Fire • Fires can result from laser use due to: • Electrical circuits (overheating/short circuits) • Improper beam enclosures • Ignition of gases/vapors/fumes in laser area • Ignition of flammable/combustible dyes • Use fire-resistant enclosures, and make sure electrical circuits are frequently checked and repaired

21. Laser Hazards – Non-Beam • UV radiation can be emitted from laser welding or cutting operations • Discharge tubes and pumping lamps may emit UV radiation • Pumping stations may emit visible and IR-A radiation • Use shielding to prevent exposure to non-beam hazards

22. Laser Classifications • Class I • Class II • Class IIa • Class IIIa • Class IIIb • Class IV • Classes can change if safety measures are bypassed or if the laser is disassembled

23. Class I • Denotes lasers or laser systems that do not, under normal operating conditions, pose a hazard. • Example: CD-ROM Drive/Players

24. Class II • Denotes low-power visible lasers or laser systems which, because of the normal human aversion response (i.e. blinking, eye movement, etc.) do not normally present a hazard, but may present some potential for hazard if viewed directly for extended periods of time (as with many conventional light sources). • Example: Supermarket Scanner

25. Class IIa • Denotes low-power visible lasers or laser systems that are not intended for prolonged viewing, and under normal operating conditions will not produce a hazard if the beam is viewed directly for periods not exceeding 1000 seconds.

26. Class IIIa • Denotes some lasers or laser systems having a CAUTION label that normally would not injure the eye if viewed for only momentary periods (within the aversion response period) with the unaided eye, but may present a greater hazard if viewed using collecting optics. • Example: Laser Pointers

27. Class IIIa • Another group of Class IIIa lasers have DANGER labels and are capable of exceeding permissible exposure levels for the eye in 0.25-seconds and still pose a low risk of injury.

28. Class IIIb • Denotes lasers or laser systems that can produce a hazard if viewed directly. This includes intrabeam viewing of specular reflections. Normally, Class IIIb lasers will not produce a hazardous diffuse response. • Example: Research Lasers

29. Class IV • Denotes lasers or laser systems that produce a hazard not only from direct or specular reflections, but may produce hazardous diffuse reflections. Such lasers may produce significant skin hazards as well as fire hazards. • Example: Research or Manufacturing Lasers

30. Basic Safety Rules for Class III • Never aim a laser at a person’s eye. • Know where a laser (especially laser pointer) is pointed at all times • Use proper safety eyewear if there is a chance that the beam or a hazardous specular reflection could expose the eyes (in excess of MPE). • Permit only experienced personnel to operate the laser and do not leave an operable laser unattended if there is a chance that the unauthorized user may attempt to operate the laser. • Applies even to laser pointers there is the potential for abuse by students or other unauthorized personnel

31. Class III Safety Rules • A key switch should be used if untrained persons may gain access to the laser. A warning light or buzzer may be used to indicate when the laser is operating. • Does not apply to many laser pointers • Enclose as much as the beam's path as practical.

32. Class III Safety Rules • Avoid placement of the unprotected eye along or near the beam axis as attempted in some alignment procedures. • The chance of hazardous specular reflections is greatest in this area. • Terminate the primary and secondary beams if possible at the end of their useful paths. • Aim laser pointers at object to be highlighted • Avoid aiming laser pointers out windows or open doors • Use beam shutters and laser output filters to reduce the beam power to less hazardous levels when the full output power is not required. • Does not apply to laser pointers

33. Class III Safety Rules • Ensure that any spectators are not potentially exposed to hazardous conditions. • Includes electrical and fire hazards, as well as from direct laser exposure • Attempt to keep laser beam paths above or below eye level at either sitting or standing position. • Operate lasers only in well-controlled areas. For example, within a closed room with covered or filtered windows and controlled access. • Does not directly apply to laser pointers

34. Class III Safety Rules • Make sure lasers are labeled with appropriate Class IIIa or IIIb warning statements. Post appropriate warning signs if personnel can be overexposed. • Mount the laser on a firm support to assure that the beam travels along the intended path. • Be aware of the laser beam path at all times, even with laser pointers

35. Class III Safety Rules • Ensure that individuals do not look directly into a laser beam with optical instruments unless an appropriate protective filter is present within the optical train. • Eliminate unnecessary specular (mirror-like) surfaces from the vicinity of the laser beam path, and avoid inadvertently aiming at such surfaces.

36. Class IV Safety Rules • Enclose the entire laser beam path if as much as possible. If done correctly, the laser’s status could revert to a less hazardous classification. • Confine open-beam indoor laser operations to a light-tight room. Interlock entrances to ensure that the laser cannot emit when the door is open, if the NHZ extends to the entrances.

37. Class IV Safety Rules • Ensure that all personnel wear adequate eye protection, and if the laser beam irradiance represents a serious skin or fire hazard, that a suitable shield is present between the laser beam and personnel. • Use remote firing and video monitoring, or remote viewing through a laser safety shield where feasible.

38. Class IV Safety Rules • Use beam shutter and laser output filters to reduce the laser beam irradiance to less hazardous levels whenever the full beam power is not required. • Ensure that the laser device has a key-switch master control to permit only authorized personnel to operate the laser.

39. Class IV Safety Rules • Install appropriate signs and labels as needed. • Use dark, absorbing, diffuse, fire resistant target and backstops where feasible. • Design safety into laser-welding and cutting equipment, and laser devices used in miniature work. If feasible, such work should be performed in a light-tight or baffled interlocked enclosure to eliminate the requirements for eye protection.

40. Common Causes of Accidents • Altering beam path without accounting for location of beam termination • Inserting reflective objects into the beam path • Bypassing interlocks • Accidentally activating power supply • Accidentally firing the laser

41. Hazard Control - Engineering • Engineering controls should be utilized in preference to administrative or PPE controls, whenever feasible • Engineering controls rely on structural or system controls to prevent exposures • Beam Housings • Shutters • Attenuators • Remote firing controls • Interlocks

42. Hazard Control - Administrative • Administrative controls can be utilized if engineering controls are determined to be infeasible. • Administrative controls rely on work practices and warnings to prevent exposures • Warning signs and labels • Standard Operating Procedures (SOPs) (OCC Laser Safety Program) • Training

43. Hazard Control – Administrative • Administrative Safety Practices • Only properly trained and authorized employees may use Class IIIb or IV lasers • Employees utilizing lasers are responsible for restricting access to the area and the proper use of the laser • Designate the NHZ for the laser for Class IIIb or IV lasers • Address non-beam hazards in work practices • Follow guidelines and procedures found in the OCC Laser Safety Program

44. Warning Labels

45. Hazard Control - Personal Protective Equipment • Use flame-resistant materials when dealing with Class IV beams • Use appropriate protective eyewear • Eyewear is characterized by Optical Density (OD) • Example: OD of 6 represents a reduction of the incident radiation by a factor of 1 million. • Eyewear must be marked with OD and wavelength for proper selection. • Eyewear must be comfortable

46. Hazard Control - Personal Protective Equipment

47. Hazard Control - Personal Protective Equipment • Properly use and maintain protective eyewear • Refer to the OCC Personal Protective Equipment Program for guidelines and requirements for protective eyewear • Inspect protective eyewear before each use for pitting, crazing, or solarization of the lenses

48. Contacts • Michael Schmidt Manager of Environmental Health and Safety • 248-232-4234 (Phone) • 248-232-4254 (Fax) • 248-467-4477 (Cell) • mschmid@oaklandcc.edu