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Presentation on theme: "LASER SAFETY REFRESHER TRAINING"— Presentation transcript:


2 LASER HAZARD CLASSES Lasers are classified according to the level of laser radiation that is accessible during normal operation and maximum level of exposure possible. Lasers may be classified under: The Federal Laser Production Performance Standard (CDRH standard) The American National Standard for Safe Use of Lasers IEC International Standard 2

ANSI Z Class 1 Incapable of causing injury during normal operation Class 1M Incapable of causing injury during normal operation unless collecting optics are used Class 2 Visible lasers incapable of causing injury in 0.25 s. Class 2M Visible lasers incapable of causing injury in 0.25 s Class 3R Marginally unsafe for intrabeam viewing; up to 5 times the class 2 limit for visible lasers or 5 times the class 1 limit for invisible lasers Class 3B Eye hazard for intrabeam viewing, usually not an eye hazard for diffuse viewing Class 4 Eye and skin hazard for both direct and scattered exposure 3

The Federal Laser Product Performance Standard (FLPPS) of the Center for Devices and Radiological Health (CDRH) This is federal law that applies to US manufacturers of lasers. The American National Standard for Safe Use of Lasers (ANSI Z136.1) This is a “best approach” VOLUNTARY Standard applying to the use of lasers, which is “recognized by” : The Occupational Safety and Health Administration (OSHA) IEC International Standard Lasers classified and labeled in accordance with this standard may be sold in the US. CDRH & ANSI Z136.1 do not agree with all the provisions of this standard. 4

Protective Housing prevents access to laser radiation above safe level. Safety Interlocks terminate laser beam if protective housing is opened. Only authorized personnel may operate laser with interlocks defeated. Warning Labels alert personnel if opening the housing might expose a laser hazard. Viewing Windows and Optics limit laser and collateral radiation to safe levels. 5

CLASS II LASER PRODUCT Laser Radiation Do Not Stare Into Beam Helium Neon Laser 1 milliwatt max/cw CLASS IV Laser Product VISIBLE LASER RADIATION- AVOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION Argon Ion Wavelength: 488/514 nm Output Power 5 W Class 2 Class 3R with expanded beam Class 3R with small beam Class 3B Class 4 The Laser Safety Officer must evaluate all lasers and labeling for safety compliance with ANSI Z136.1 recommendations. 6

INVISIBLE LASER RADIATION AVOID EYE OR SKIN EXPOSURE TO DIRECT OR SCATTERED RADIATION CLASS 4 LASER PRODUCT WAVELENGTH ,600 nm MAX LASER POWER W EN Symbol and Border: Black Background: Yellow Legend and Border: Black Background: Yellow The Laser Safety Officer must evaluate all lasers and labeling for safety compliance with ANSI Z136.1 recommendations. 7

8 LASER SPECTRUM UV -- potential photochemical damage (eyes and skin)
avoid long term hazardous exposures at low levels VISIBLE LIGHT nm seeing light helps avoid hazardous exposures NEAR IR (NIR) nm Is poorly or cannot be seen, but the eye does focus these wavelengths on the retina, producing an invisible retinal hazard and the potential for serious eye injury. The most stringent laser safety precautions are required in this wavelength range, which contains several of the most useful lasers. FAR IR -- COMPLETELY ABSORBED BY WATER BEFORE (REACHING) RETINA Can damage other parts of the eye, but absorption spread over a larger area, allowing larger exposures

Spectral characteristic – Wavelength In general, shorter wavelengths are more hazardous in any spectral region, but Near Infrared lasers are the most hazardous because they are invisible retinal hazards. Temporal characteristic – Pulse Duration In general, pulsed lasers are more hazardous than CW lasers. The shorter the pulse duration, the higher the peak power and the greater the hazard. Spatial characteristic – Beam Divergence Low beam divergence results in a large intra-beam hazard distance. Focusing characteristic High retinal irradiance of focused beam creates extreme retinal hazard for visible and near infrared lasers. The absorption of various wavelengths within the eye and the variation of hazard because of wavelength will be examined in detail in the next section.

Retinal (macular region) injury produced by four pulses from a Nd:YAG laser. Pulse duration ~20 ns Pulse energy ~15 mJ – 7500x the safe level (maximum permissible exposure – MPE) Each pulse -- tiny explosion/shockwave -- severe damage 3 weeks later -- permanent destruction of the macular region. Visual acuity ~20/400 and will not improve. Short pulse lasers produce the greatest eye hazards. This injury could not have occurred if the individual had been wearing the appropriate laser safety eyewear. Photo courtesy of U S Army Center for Health Promotion and Preventive Medicine

Studies of laser accidents have shown that there are usually several contributing factors. The following are common causes of laser injuries: Inadequate training of laser personnel Alignment performed without adequate procedures Failure to block beams or stray reflections Failure to wear eye protection in hazardous situations Failure to follow approved standard operating procedures or safe work practices Don’t risk yours or another’s safety – WORK SAFE

12 OVERVIEW OF ANSI Z136.1 The ANSI Standard is a guideline for decision making. Laser users trained in accordance with the standard are expected to take individual responsibility for the safe use of all lasers. The OSHA Technical Manual, Section III, Chapter 6, LASER HAZARDS is available at This document can serve as an effective reference for laser safety programs. It is not necessary to have a copy of the ANSI Standard or be an expert in the details of that standard to maintain an effective laser safety program. 1. MANAGEMENT APPOINTS LASER SAFETY OFFICER 2. LSO VERIFIES LASER CLASSIFICATION 3. LSO EVALUATES HAZARDS BY DETERMINING MPE OD NHZ 4. LSO SPECIFIES CONTROL MEASURES ENGINEERING CONTROLS ENCLOSURES INTERLOCKS WARNING SYSTEMS ADMINISTRATIVE AND PROCEDURAL CONTROLS AUTHORIZED PERSONNEL SOP (INCLUDING ALIGNMENT) TRAINING PROTECTIVE EQUIPMENT EYEWEAR BARRIERS 12

13 Laser Hazard Evaluation REQUIREMENT
PRIOR TO USE each Class 3b or 4 laser/laser system must be evaluated for the following hazards by the LSO 1. Calculation of: Maximum Permissible Exposure Optical Density of Eyewear Nominal Hazard Zone -- Each of these is explained in the following slides. 2. Evaluation of laser use environment (hazards) Required controls 3. Operator evaluation Training Level of responsibility assumed by AU The personnel who may be exposed to laser radiation 13

14 Maximum Permissible Exposure (MPE)
The level of laser light to which a person may be exposed without risk of injury. primary factors effecting MPE: exposure type (Intrabeam eye exposure -- worst case) wavelength pulse characteristics exposure duration 0.25 s -- visible laser 10 s -- invisible laser 14

15 Irradiance based on area of
OPTICAL DENSITY OF LASER SAFETY EYEWEAR Laser E0 MPE Eyewear Irradiance based on area of Limiting Aperture (Table 8) OD = log E0 MPE Optical Density – logarithmic expression of filter attenuation Or worst case OD (based on the assumption that the entire beam enters the eye) beam diameter, smaller than pupil -- the hazard does not increase worst situation -- largest beam possible enters eye (produces smallest spot on the retina) OD % Transmission % % % % % % % The laser safety officer will assist in determining appropriate optical densities for each wavelength of class 3B & 4 lasers. 15

16 NOMINAL HAZARD ZONE Intrabeam Nominal Hazard Zone Diffuse Reflection
The space within which the potential exposure exceeds the MPE, or distance required for divergence to decrease irradiance below MPE. This is often a large distance, consequently safe use requires termination on a diffuse reflecting beam block. Diffuse Reflection Nominal Hazard Zone LASER Intrabeam Nominal Hazard Zone LASER The diffuse reflection NHZ is the distance that scattered irradiance levels exceed MPE. A diffuse reflection is an omnidirectional hazard. The LSO determines NHZ exposure condition (intrabeam, diffuse reflection, focusing lenses, optical fibers, etc.) 16

All users of lasers with exposed beams should: Understand the hazards associated with the laser they use Evaluate the control of hazards every time they operate the lasers Use their best judgment in controlling all laser hazards (be conservative; don’t take chances) Consult their Laser Safety Officer whenever they have safety concerns or questions 17

ANSI Section 4.1 “Control Measures shall be devised to reduce the possibility of exposure of the eye and skin to hazardous levels of laser radiation.” Types of Control Measures Engineering -- built into equipment or facility (AUTOMATIC PROTECTION) Administrative -- POLICIES (i.e., only authorized personnel may operate lasers) Procedural – working procedures (STANDARD OPERATING PROCEDURE) LSO determines CONTROL MEASURES to reduce possible laser EXPOSURES < MPE for all CLASS 3B/4 18

Laser Class 1 System Laser Some scattered light escapes. NHZ is small. LIMITED OPEN BEAM PATH FULLY OPEN BEAM PATH Laser Larger NHZ requires laser controlled area. 19

Section Laser Controlled Area -- Class 3B Or 4 Lasers with exposed beams access to the area is controlled laser hazards are controlled -- engineering & procedural controls specified in SOP some individual is in control of the laser hazards. LASER WARNING SIGN must always be posted at the entryway to a CLASS 4 laser controlled area Eye Protection Laser safety eyewear must be used inside the controlled area as specified in the SOP. Beam Control Barriers, shrouds, and beam stops are used to limit the NHZ inside the controlled area. Administrative and Procedural Controls Administrative and procedural controls define approved personnel and procedures. Written Standard Operating Procedures (SOPs) are required for class 4 lasers Education and Training Only trained personnel are allowed inside the laser controlled area 20

Section ENTRYWAY CONTROLS ARE REQUIRED FOR CLASS 4 LASER CONTROLLED AREAS. 1. Non-Defeatable Entryway Controls -- terminates laser beam with opened door Doorway interlock is non-defeatable Training of authorized users only 2. Defeatable Entryway Controls -- may be bypassed allowing entrance/exit controlled area without laser operation interruption Doorway interlock is defeatable during “non-hazardous operation “ Requires training of all personnel with access Requires barrier and eyewear at door 3. Procedural Entryway Controls – only when hazards are well controlled and if all personnel with access are trained in laser safety. No doorway interlock Training of all personnel with access Barrier and eyewear at door Visible or audible signal at doorway LABORATORY DOORS may be LOCKED during laser operation, but there must be provisions for EASY EMERGENCY INGRESS AND EGRESS.

LASER PROTECTIVE BARRIERS/CURTAINS -- limits NHZ inside laser controlled areas barriers also used to protect entryways, computer work stations, and workbenches NO direct optical path may exist between laser optics tables and computer stations in laser laboratories. Photos courtesy of 22

23 CURBS ON OPTICAL TABLE Beam control is improved by using curbs on optical table, especially when all beams are horizontal. Curbs on the optical table block any reflections and confine the hazard to the area of the optical table. These curbs may be removed easily to provide greater access for reconfiguration or alignment. 23

24 BEAM CONTROL METHODS LIMITING the NHZ inside a laser controlled area greatly enhances safety in a laser laboratory. use beam blocks, beam tubes, partial enclosures, and curbs on optical tables In many cases the NHZ can be confined to the optical table. IT’S NOT NECESSARY to interlock all enclosures inside laser laboratories appropriate labels should always be applied to alert workers to potential laser hazards 24

25 LASER SAFETY EYEWEAR Laser safety eyewear is available in glass or plastic for all laser wavelengths. The required Optical Density of the eyewear is determined in the hazard analysis performed by the LSO. EYEWEAR SHOULD NEVER BE VIEWED AS THE FIRST CONTROL MEASURE TO BE APPLIED. In all cases ENGINEERING AND PROCEDURAL CONTROLS should be devised to reduce and limit the possible exposure to hazardous laser light. eyewear should then be required as a LAST LINE OF DEFENSE in case everything else fails. Most laser Eye Injuries have occurred when Other Controls Proved Inadequate and the worker was Not Wearing Eyewear. EYEWEAR WOULD HAVE PREVENTED MOST LASER EYE INJURIES, BUT IT DOES NOT MAKE THE WEARER INVULNERABLE. It is never safe to stare into a laser beam, even if wearing laser protective eyewear. THE GREATEST RISK OF EYE INJURY OCCURS WHEN NEAR IR LASERS ARE OPERATED WITH THE BEAM EXPOSED. 25

26 All eyewear must be labeled with wavelength and optical density.
EYEWEAR LABELS Optical Density curves for all eyewear are available from the manufacturers. IN RESEARCH SITUATIONS it is sometimes necessary to use eyewear that is NOT LABELED FOR THE SPECIFIC WAVELENGTHS IN USE. IN THESE CASES, EYEWEAR DATA MUST BE AVAILABLE IN THE LABORATORY. All eyewear must be labeled with wavelength and optical density. 26

The person operating the laser always has the primary responsibility for all hazards associated with laser use. If YOU create laser photons, YOU ARE RESPONSIBLE for the safety of anyone who might be exposed to those photons. 1st RESPONSIBILITY OF LASER USERS -- ASSURE THE SAFETY OF OTHERS 2nd -- protect Yourself SECTION OF THE ANSI STANDARD STATES: “Employees who work with lasers or laser systems and their supervisors have responsibilities for establishing the safe use.” 27

28 SUGGESTED SOP FORMAT ANSI Standard - Must be written, available at the laser, and include alignment methods – REQUIRES LSO APPROVAL (CLASS 3B/CLASS 4 LASERS) 1. Introduction – Description of laser Type and wavelength; Intended application & Location Average power or energy per pulse Pulse duration and repetition rate for pulsed lasers 2. Hazards – List all hazards associated with laser Eye and skin hazards from direct and diffuse exposures Electrical hazards Laser generated air contaminants Other recognized hazards 3. Control Measures – List control measures for each hazard Include the following: Eyewear requirement, include wavelength and OD Description of controlled area and entry controls Reference to equipment manual Alignment procedures (or guidelines) 4. Authorized Personnel 5. Emergency Procedures 28

29 SAFE BEAM ALIGNMENT Most beam injuries occur during alignment.
Only trained personnel may align class 3B or class 4 lasers (NO EXCEPTIONS!) Laser safety eyewear is required for class 3B and class 4 beam alignment. ANSI REQUIRES approved, written alignment procedures for ALL class 4 laser alignment activities and recommends them for class 3B. 29

CLASS 3b AND 4 LASERS 1. Exclude unnecessary personnel from the laser area during alignment. 2. Where possible, use low-power visible lasers for path simulation of high power visible or invisible lasers. 3. Wear protective eyewear during alignment. Use special alignment eyewear when circumstances permit their use. 4. When aligning invisible beams, use beam display devices such as image converter viewers or phosphor cards to locate beams. 5. Perform alignment tasks using high-power lasers at the lowest possible power level. 6. Use a shutter or beam block to block high-power beams at their source except when actually needed during the alignment process. 7. Use a laser rated beam block to terminate high-power beams downstream of the optics being aligned. 8. Use beam blocks and/or laser protective barriers in conditions where alignment beams could stray into areas with uninvolved personnel. 9. Place beam blocks behind optics to terminate beams that might miss mirrors during alignment. Locate and block all stray reflections before proceeding to the next optical component or section. Be sure all beams and reflections are properly terminated before high-power operation. Post appropriate area warning signs during alignment procedures where lasers are normally class 1. 13. Alignments should be done only by those who have received laser safety training. 30

31 SAFE WORK PRACTICES Never intentionally look directly into a laser. Do not stare at the light from any laser. Allow yourself to blink if the light is too bright. Do not view a Class 3a (or any higher power) laser with optical instruments. Never direct the beam toward other people. Operate lasers only in the area designed for their use and be certain that the beam is terminated at the end of its use path. Never allow a laser beam to escape its designated area of use. Position the laser so that it is well above or below eye level. Always block the beam with a diffuse reflecting beam block. Remove all unnecessary reflective objects from the area near the beam’s path. This may include items of jewelry and tools. Do not enter a designated Class 3b or Class 4 laser area (posted with a DANGER sign) without approval from a qualified laser operator. Eye protection is required in these areas. Always wear laser safety eyewear if a class 4 invisible beam is exposed. 31


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