Laser Safety Guide 77 Massachusetts Avenue Cambridge, MA 02139 (617)-452-3477 [email protected] ehs.mit.edu Delegation of Authority Registration Process Laser Classification Summary MIT has a standing institute Committee on Radiation Laser Registration for Class 3B and Class 1* Incapable of causing injury during normal Protection to oversee all uses of radiation at the Institute Class 4 lasers and laser systems operations and its associated off campus locations. The Committee Class 1M Incapable of causing injury during normal gives the RPP authority to stop any experiment or process Follow these steps: operations unless collecting optics are used involving radiation that is deemed unsafe. 1. Complete form A: Laser Registration 2. Complete form B: Laser Inventory Class 2 Visible lasers incapable of causing injury in Massachusetts Department of Public Health regulate 3. Complete form C: Safety Procedure 0.25s. the use of radiation sources including lasers. They perform 4. RPP will perform a Hazard Assessment Class 2M Visible lasers incapable of causing injury in unannounced inspections of laser facilities. 0.25s unless collecting optics are used (typically <1mW) Radiation Protection Program (RPP) acts as the RPC’s To register a laser with RPP, and more, operational arm by serving the institute through training, visit the laser safety webpage at Class 3R Eye hazard for chronic viewing or use of oversight/risk assessment of laser use, and providing day to ehs.mit.edu/radiological-program/laser-safety/ collecting optics (typically 1-5 mW) day support for all matters pertaining to lasers. Class 3B Eye and skin hazard for direct beam exposure (5-500 mW). Principle Investigators (PI), Lab Supervisors (LS), and Lab Laser Safety Procedure Class 4 Eye and skin hazard for direct beam and Representatives (LR) work with RPP to develop and scattered radiation; also a fire hazard maintain a safe work environment in the laser lab. (>500 mW) • The Laser Safety Procedure (LSP) is a How to Dispose of a Laser short guidance document outlining the *Any laser can be reclassified as a Class 1 with safe use of the laser. proper enclosures installed and safeguards in place. For Class 3B and Class 4 laser(s) and laser system(s): • This procedure will include laser control measures, access control, and Laser Training Requirements 1. Contact RPP to discuss decommissioning plans. Eyewear requirements as a minimum, All Laser Users must complete the following training: 2. Remove all means of activating the laser (electrically • It should also include alignment • Laser Safety Training — EHS00371 deactivated) or destroy the laser (rendered inoperable). procedures (when applicable). • Laser Laboratory Specific Training given by an 3. Review manufacturer laser manual for a complete list of • All personnel working with this laser experienced member in the lab hazardous materials within the device. must follow this procedure. The LSP is • Follow the Laser Safety Procedure (LSP) 4. Remove and properly dispose of any hazardous part of the laboratory specific training. materials such as mercury, batteries, oils, dyes, • This is required for all Class 3B and Beryllium oxide (BeO) or other chemicals that are Class 4 Laser systems Emergency Procedures contained in the laser system. 5. Contact RPP for decontamination verification and final REMEMBER, the person operating the Follow emergency procedures established in the LSP disposal options for the laser system. laser has the primary responsibility for Disable machine (Emergency Off, shut-down, unplug) 6. Remove MIT Property tag from the system and contact ALL hazards associated with its use. Seek medical attention (if needed) - Dial 100 or the Facilities department for disposal assistance. 617-253-1212 (cell) For outdoor propagation, contact RPP Contact Radiation Protection for an incident review Safe Work Practices Laser Hazards Laser Safety Terminology Maximum Permissible Exposure (MPE): • Never intentionally look directly into laser light. Primary Beam Hazards Intrabeam viewing The level of laser radiation to which a person may be • Do not fight the eye’s blink or aversion response. exposed without experiencing hazardous effect or • Never direct the beam toward people or doors. adverse biological changes in the eye or skin. • Never allow a laser beam to escape from its Scattered Beam Hazards Accessible Emission Limit (AEL): designated area of use. Allowed emission within a certain laser hazard class. Specular reflection • Remove all unnecessary reflective objects from Nominal Hazard Zone (NHZ): the area near the beam path. This may include The space within which the irradiance or radiant exposure watches, jewelry, or tools. exceeds the appropriate MPE. Nominal Ocular Hazard Distance (NOHD): • Position the laser so that it is well above or Diffuse reflection (Class 4 only) The distance along the axis of the unobstructed beam below eye level (both standing and sitting). from a laser, fiber end, or connector, to the human eye • When not in use, a laser should be stored to Most Hazardous Act – Beam Alignment beyond which the irradiance or radiant exposure is not prevent unauthorized use. Estimated ~1/3 of all (known) accidents, ~ 60 -70 % expected to exceed the MPE. of all known laboratory accidents. Laser Characteristics Common Scenario: unanticipated reflection from Biological Response an optic while not wearing protective eyewear Non-Beam Hazards Skin Injury: - Electrical (Keep equipment off the floor) All Wavelengths: 2 - Fire (irradiances exceeding 10 W/cm ) Thermal, Skin Burns - Chemical (Excimer and dye lasers) For <550 nm: - Laser generated airborne contaminants Photochemical, skin cancer, “tanning”, Laser Eye Protection (LEP) photosensitive reactions (can be The optical density (OD) of medication related) LEP represents an order of Keratitis and Photochemical Burning magnitude reduction of the Eye Injury: conjunctivitis and thermal of the Beam Characteristics Active Medium laser light reaching the eye See: Flash or after (pink eye) injury of the cornea - Wavelength - Gas Eye Cataract retina Eye Cataract Laser entering eye image in opposite - Divergence - Solid State OD = 3 color OR difficulty - Diameter - Diode detecting blue or - Fiber Optics - Dye Laser beam green colors @ 1000 x MPE - Pulse Repetition Rate - Fiber Laser All LEP must be labeled Feel: Burning pain - Continuous ≥ ¼ sec on cornea - Pulsed < ¼ sec Hear: “Pop” sound A 100 Watt light bulb has 100,000 times LEP Inspection the power of • Match eyewear to laser (OD and Wavelength) a 1 mW laser. • Inspect the lens (white marks, blemishes, The same pits/digs, surface scratches, coating tack) laser is 2-10 • Inspect the frame (broken, cracked, loose strap) million times • Evaluate the fit (gaps between frame and face) brighter. Hazard Assessment Controlled Area Requirements • Contact the Radiation Protection Program after obtaining • Only individuals trained in laser safety are • Key switch, Area interlocks (depends on system), any new laser systems. allowed access to the laser controlled area and remote firing or remote viewing (depends • The Laser Safety Officer (LSO) will evaluate the LSP and (Class 4 only). on system) perform a Hazard Assessment of the lab, verify required • Use only diffusely reflecting materials in or • Only individuals trained in the operation of the eyewear, and supply the lab with proper signage. near the beam path. laser and laser safety may operate the laser • Secure the laser beam path to be above or system. Emergency Power Off below eye level. • Path of the laser light is well defined and • • An Emergency Power Off (EPO) for the laser Facility is under the direct supervision of an controlled (curbs, beam traps/blocks, external system is REQUIRED for Class 4 Systems. individual knowledgeable in laser safety. shutters, curtains). • • • The EPO must be labeled and ideally should be Access is limited and requires approval to Hazardous beams are terminated using beam located on the laser table or at table level. enter. stops. • • • SOP must state what the EPO controls. Store lasers in a manner that prevents the All light levels in excess of the MPE must be unauthorized use. confined to the laser table if feasible - establish Posting Requirements • Light tight room (depends on system – Nominal Hazard Zone (NHZ). required for Class 4) NOTICE signs are required for all DANGER signs are laser-specific temporary laser system setups and must be posted at the lab Eyewear Storage Interlock Systems including alignments. entry point. • Proper storage reduces damage and extends eyewear lifetime Interlock systems that are tied to • Helps to keep eyewear from the illuminated warning sign and being misplaced possibly to the operation are • Store similar eyewear together sometimes required. for ease of access Access Control Class 3B and Class 4 laser labs require access control. • Flashing sign indicates Self-closing device on door is a when system is on requirement for laser labs • Standard keyed lock should not be used, too many people have “master keys” • Key card or Cipher locks are Laser warning sign preferred stating wavelength, OD, and power Space is often limited in the lab, but efforts need to be taken to laser users sufficient walkway space around the lab and equipment. • Minimum aisle clearance of 24” Main aisles used for emergency egress must have clearance of 36” • Consider cable management Controlling the Beam Beam Alignment Fibers It is a best practice in laser safety to point the beam • Use the minimum beam power /