Lasers (Download)
Lasers http://www.rainydaymagazine.com/RDM2007/Home/Oct2007/RainyDayScience/WickedLaser/FocusedBeam2Big.jpg Laser L Light A Amplified By S Stimulated E Emission of R Radiation “ Thus the laser is a device which produces and amplifies light.” OSHA STD 01-05-001 – PUB 8-1.7 – Guidelines for Laser Safety and Hazard Assessment A Brief History The mechanism by which this stimulated emission is accomplished was first postulated by Albert Einstein in 1917. Lasers have been used in construction since the mid 70’s. Lasers came to be used in construction to improve the performance of existing tools. The accuracy of lasers has helped improve the accuracy of construction by helping to eliminate problems due to inaccuracy in measurements. This is why lasers have become increasingly popular since their introduction to the industry. OSHA STD 01-05-001 – PUB 8-1.7 – Guidelines for Laser Safety and Hazard Assessment Laser Safety There are 2 different types of lasers in construction Type 1 Invisible Lasers These lasers are generally used in exterior settings for checking grade, setting concrete forms, checking depths of footers and trenches, and more advanced uses include setting elevations for laser receivers mounted on excavators and motor graders. OEMBuddy.com www.jamesriversupply.com/whatis.htm http://web.princeton.edu/sites/ehs/laserguide/sec3.htm#class1 Laser Safety Type 2 Visible Lasers These types are usually used in indoor applications such as: Using a laser as a plane of light Setting sewer pipe Hang ceiling grids Aligning and mounting floor and ceiling brackets for walls Aligning studs Leveling and hanging cabinets Any other application where a level is used. OEMBuddy.com www.jamesriversupply.com/whatis.htm http://web.princeton.edu/sites/ehs/laserguide/sec3.htm#class1 Laser Safety Typical Hazards Burning eye and retina damage Burning skin creating blisters Many accidents occur when someone is using a laser but is not paying attention to their surroundings and gets injured by something else such as getting struck by equipment. http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=DIRECTIVES&p_id=1705 How lasers can do harm The laser produces an intense, highly directional beam of light. The most common cause of laser-induced tissue damage is thermal in nature, where the tissue proteins are denatured due to the temperature rise following absorption of laser energy. It is now widely accepted that the human eye is almost always more vulnerable to injury than human skin. Laser Safety Laser Safety Statistics Although there have been no recorded fatalities from lasers, there are many cases of people using a laser and not paying attention to their surroundings. Then they have been involved in the following types of accidents: Struck by Trench cave in Crushed by Caught between Fall http://www.osha.gov/OshDoc/toc_FatalFacts.html http://www.issm-iseb.org/b2b/pics/Motor_Grader__PQ190II_.jpg Typical Accident When Using Lasers A worker and coworkers were constructing a driveway. One worker was operating a dozer while another worker was behind the dozer measuring the grade of the earth with a laser. The bulldozer backed over the second worker. He was crushed and killed. OSHA Fatality Data 1990 to 2009 A worker was attempting to shoot a grade with a laser device in a trench. The trench had no protective system in use to protect employees from cave-in hazards. The worker entered the trench to find the laser (light) with a shovel. His legs were then trapped at the knees due to a small cave-in on the west side of the excavation. During the rescue attempt, both the worker and a dozer operator (who tried to assist in the rescue) were buried due to a collapse of the east wall of the trench. OSHA Fatality Data 1990 to 2009 Typical Accident When Using Lasers Two workers were instructed to replace a storm drain concrete pipe in a section of a trench. An operator of an excavator was nearby but working on a different portion of the trench. Employee #2 removed a bucket of dirt and swung around and dumped the bucket of dirt onto the spoil pile. As the operator was moving a bucket of material, he heard one of the workers yelling. The worker was buried up to his neck in the dirt. When the worker was being removed from the trench, he lost consciousness and went into cardiac arrest. Since no witnesses observed the accident, the situation had to be surmised. The workers in the trench had utilized a laser and target during the course of their work. The laser was utilized to ensure that the pipe was installed at the proper grade. The trench had not been properly supported to prevent the cave-in. OSHA Fatality Data 1990 to 2009 Laser Fatality Example Laser Safety Classes of Lasers Class I Example: Laser Printer, CD players Less than .4 mW of power output Not harmful Class II Example: Laser Pointers Between .4 and 1 mW of power output Can be harmful over an extended period of time Class III III(a) between 1 and 5 mW Example: Laser pointers Injury if stared at III(b) between 5 and 500 mW Example: Laser Light show Injury if looked at directly or from reflection Class IV Example: Cutting, Welding Over 500 mW power output Most dangerous: can cause ignition of materials OSHA STD 01-05-001 – PUB 8-1.7 – Guidelines for Laser Safety and Hazard Assessment http://www.force.dk/NR/rdonlyres/2AD0D02F-15A1-4681-851F-F01C357CB662/0/051215_laser_100x90.jpg http://74.125.47.132/search?q=cache:sjIB7KgYljsJ:ehs.uky.edu/radiation/laser_fs.html+class+2+laser+examples&cd=3&hl=en&ct=clnk&gl=us Class I and II “Caution” The lasers under Class I and II are usually considered “safe” to human eyes. That means human eyes exposed to the laser radiation would not sustain permanent retina damage. It is also suggested that people do not look into the laser beam a long time or view the beam directly with optical instruments . Laser Safety Class IIIa and IIIb “Danger“ It is generally thought that the beam will be unsafe to human eyes. To expose eyes to the laser radiation would result in a permanent retina damages. Direct eye or skin exposure to the laser beam is prohibited. Laser Safety Class IV “Danger“ The powerful radiation including the reflected and scattered radiation can permanently cause human skin and eye retina damages. It is important to avoid eye or skin exposure to direct or scattered radiation. The Class IV lasers should be used strictly under the professional control. Laser Safety Training The level of training shall be appropriate to the level of the laser hazard being used (ANSI 5.5). designated by the supervisor to provide training according to EH&S. • Class I and II – training not required • Class IIIa– training not required • Class IIIb and 4 – training is required Refresher training is required every two years. Attendance at a laser safety class or completing an on-line refresher course will meet this requirement. http://www.ehs.cornell.edu/file/Laser_Safety_Program_Guide_v2.pdf Laser Safety Laser Safety OSHA Authority for 1910 Subpart I – Personal Protective Equipment 1910.133(a)(5) – Eye and face protection The employer shall ensure that each affected employee uses equipment with filter lenses that have a shade number appropriate for the work being performed for protection from injurious light radiation. http://www.westernsafety.com/guardair/osha_big_fn.jpg http://www.ee.byu.edu/photonics/safety.parts/images/goggles.bmp http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=DIRECTIVES&p_id=1705 1910.269(w)(8) “Lasers.” Laser equipment shall be installed, adjusted, and operated in accordance with 1926.54 of this Chapter Laser Safety 1926.54 (a through l) Example: 1926.54(b) Proof of qualification of the laser equipment operator shall be available and in possession of the operator at all times. 1926.54(c) Employees, when working in areas in which a potential exposure to direct or reflected laser light greater than 0.005 watts (5 milliwatts) exists, shall be provided with antilaser eye protection devices as specified in Subpart E of this Laser Safety http://www.ehs.cornell.edu/file/Laser_Safety_Program_Guide_v2.pdf Responsibilities Principle Investigator or Supervisor : health and safety of those reporting to him/her ensuring that lasers are properly installed and used laser users have been properly trained that their laser installations comply with the goals and requirements of this guide Laser Users : Each laser user is responsible for the safe operation of his/her laser LSO (Laser Safety Officer): responsible for assuring that laser hazards are evaluated and appropriate safety measures are implemented by the PI and users Laser Safety Laser Safety Best practices Always wear the necessary PPE for the type of laser to be used Make sure the work area is clear and safe before using some high powered lasers Lasers above 1mW power output Be sure to protect the laser and its components Construction lasers can be very expensive http://www.consultwebs.com/ncphotos/dc/surveyers_7413_550_dpwm.jpg http://www.osha.gov/pls/oshaweb/owadisp.show_document?p_table=DIRECTIVES&p_id=1705 Laser Safety REMEMBER TO: Post signs when using lasers Make others aware if using lasers Tape off the section where work is being done if the laser is a Class III(b) or Class IV And ALWAYS avoid pointing lasers at people ALWAYS: Wear proper PPE Know what class laser will be used Be aware of the surroundings to avoid accidents Lasers are helpful tools in many ways but it is important to know how to use them safely. THINK SAFETY WORK SAFELY