Presentation on theme: "Safe use of Class 3B and 4 Lasers"— Presentation transcript:
1Safe use of Class 3B and 4 Lasers Department of PhysicsSafe use of Class 3B and 4 LasersOctober 12th 2011Duncan McCallumHealth and Safety Coordinator
2IntroductionIntroduction to Safe use of Class 3B and 4 Lasers In the Physics departmentDepartmental Laser safety officerProf A.P. MonkmanHealth and safety co-ordinatorDuncan McCallum
3Class 3B and 4 Laser Class 3B and 4 Laser use in Physics These lasers present a high level of HazardPotential of injury to eyes and skinEye Damage is usually irreversible
4Health and SafetyFailure to follow the Universities policies can result in serious consequences in terms of :-Personal injury to oneself and othersLegal liability for individuals and for the universityIn serious cases prosecution by the HSE
5LASER LASER stands for: Light Amplification by the Stimulated Emission ofRadiation
6Lasers Description Lasers can be described by: which part of the electromagnetic spectrum is represented:InfraredVisible SpectrumUltravioletthe length of time the beam is active:Continuous WavePulsedUltra-short Pulsed
7Synchronous, monochromatic, directional light waves Laser LightLaser lightis monochromatic, unlike ordinary light which is made of a spectrum of many wavelengths. Because the light is all of the same wavelength, the light waves are said to be synchronous.is directional and focused so that it does not spread out from the point of origin.Asynchronous, multi-directional light.Synchronous, monochromatic, directional light waves
8LASER BASICS -DESIGN- Lasing Medium (gas, liquid, solid, semiconductor)- Excitation Mechanism (power supply, flashlamp, laser)uses various methods to raise the media to the lasing state.- Feedback Mechanism (mirrors)- Output Coupler (semi-transparent mirror)Lasing mediumFeedbackmechanismOutputcouplerExcitation mechanism
9Laser Media Solid state lasers Gas lasers Excimer lasers (a combination of the terms excited and dimers) use reactive gases mixed with inert gases.Dye lasers (complex organic dyes)Semiconductor lasers (also called diode lasers)There are different safety hazards associated with the various laser media.
10Electromagnetic Spectrum Laser wavelengths are usually in the Ultraviolet, Visible or Infrared Regions of the Electromagnetic Spectrum.
13Common Visible Light Lasers VioletHelium cadmium441 nmBlueKrypton476 nmArgon488 nmGreenCopper vapor510 nm514 nm528 nmFrequency doubled Nd YAG532 nmHelium neon543 nmYellow568 nm570 nmRohodamine 6G dye (tunable)594 nmOrange610 nmRedGold vapor627 nm633 nm647 nmRohodamine 6G dye650 nmRuby (CrAlO3)694 nmThe wavelength range for light that is visible to the eye ranges from nm.
14Leading Causes of Laser Accidents Unanticipated eye exposure during alignmentAvailable eye protection not usedEquipment malfunctionImproper methods for handling high voltage (This type of injury has resulted in death.)Inadequate trainingFailure to follow SOPFailure to provide non-beam hazard protection.Equipment improperly restored following serviceIncorrect eyewear selection and/or eyewear failure
15BEAM RELATED EFFECTSEye relatedEye damage caused by the laser is usually permanentSkin relatedMost skin damage caused by the laser is temporary
16EYE RELATED - Injury can result from exposure to: - direct beam- specular reflection- diffuse beam (tissue reflection)- Damage dependent on:- intensity lens of eye can focus beam ontothe retina (dye laser)- Wavelength - absorbed by different parts ofthe eye (CO2 - cornea, sclera)- duration fraction of second, before youcan blink
18Retinal Hazard RegionThe wavelength range of light that can enter the eye is 400 to 1400 nm, though the range that we can actually see is only 400 – 760 nm.The eye can focus a collimated beam of light to a spot 20 microns in diameter on the retina (called the focal point).This focusing ability places the retina at risk when exposed to laser light in the wavelength range that will penetrate to the retina, because even fairly low wattage laser light can impact the retina with 100,000 times the radiant power that entered the eye. Because of this optical gain, laser light in the 400 – 1400 nm is referred to as the Retinal Hazard Region.This is important to remember when working with infrared lasers, because the retina can be injured even though the laser is invisible.
20Biological Hazards - Retina Thermal damage (a thermal burn) to the retina occurs in the Retinal Hazard Region (from 400 nm – 1400 nm).Photochemical damage is severe at shorter visible wavelengths (violet & blue) and is cumulative over a working day.Acoustic shock from exposure to high energy pulsed lasers induce shock waves that cause tissue rupture and results in physical tissue damage.
21Biological Hazards – Cornea & Lens Ultraviolet and far-infrared laser radiation is absorbed at the cornea or lensInflammation injury to the cornea is caused by ultraviolet (UV) wavelengths ( nm). This is the same type of injury that is caused by snow blindness.Chronic exposure can cause cataract formation in the lens of the eye. At high intensities, immediate thermal burns occur, while lower exposures may lead to the development of cataracts over a period of years.CorneaLens
22Examples of EYE Damage Retinal injury from a dye laser Corneal injury from CO2 laserRetinal injury from a dye laser
23Protect Your Eyes!In a fraction of a second, your vision can go dark.
24Types of Reflections Types of Reflections Specular reflection is a reflection from a mirror-like surface. A laser beam will retain all of its original power when reflected in this manner. Note that surfaces which appear dull to the eye may be specular reflectors of IR wavelengths.Diffuse reflection is a reflection from a dull surface. Note that surfaces that appear shiny to the eye may be diffuse reflectors of UV wavelengths.Diffuse laser light reflection from a high powered laser can result in an eye injury
25Specular Reflection Specular Reflection Specular reflection is a reflection from a mirror-like surface. A laser beam will retain all of its original power when reflected in this manner.Note that surfaces which appear dull to the eye may be specular reflectors of IR wavelengths.
26Diffuse Reflection Diffuse Reflection Diffuse reflection is a reflection from a dull surface.Note that surfaces that appear shiny to the eye may be diffuse reflectors of UV wavelengths.
27Biological Hazards - Skin Ultraviolet (UV)UV can cause skin injuries comparable to sun burn.As with damage from the sun, there is an increased risk for developing skin cancer from UV laser exposure.Thermal InjuriesHigh powered (Class 4) lasers, especially from the infrared (IR) and visible range of the spectrum, can burn the skin and even set clothes on fire.
28Non-Beam HazardsNon-beam hazards refer to anything other than the laser itself that can create a hazard. This type of hazard includes:Electrical HazardsFire HazardsLaser Generated Air Contaminants (LGAC)Compressed GasesChemical HazardsCollateral and Plasma RadiationNoise
29Non-Beam Hazards – Electric Shock and Fire Electric Shock Use caution when working on or near the high-voltage power supplies used for high-power Class 3 and 4 lasers; there is sufficient voltage in these power supplies to injure or kill.Fire High powered Class 4 lasers will easily ignite flammable materials (such as paper or flammable liquids).. In some circumstances, Class 3B lasers could also ignite flammable liquids.
30Collateral & Plasma Radiation Collateral radiation refers to radiation that is not associated with the primary laser beam. This collateral radiation may be produced by power supplies, discharge lamps and plasma tubes. This radiation can be any type of EM radiation, from x-rays to radio waves.High powered lasers can also produce Plasma Radiation from the interaction of the laser beam with the target material, especially when these lasers are used to weld metals. Plasma radiation may contain enough UV and/or blue light to require additional protective measures.
31Laser Generated Air Contaminants (LGAC) Air contaminated due to interaction of laser beam with target material can result in the production of toxic chemicals.To prevent personnel from inhaling the LGAC and to prevent the release of LGAC to the environment, exhaust ventilation with special filters may be needed.
32Laser Operator Responsibilities Following laboratory administrative, alignment and standard operating procedures while operating lasers.Keep the Principal Investigator/Supervisor fully informed of any departure from established safety procedures. This includes notification of an exposure incident.Attending the Departments Laser Safety Training program or viewing the on-line Laser Safety power point training
33PPE for EyesPersonnel Protective Equipment (PPE) for eyes exposed to Class 3B or 4 lasers is mandatory. Eyewear with side protection is best. Consider these factors when selecting eyewear:Optical Density (OD) of the eyewearLaser Power and/or pulse energyLaser Wavelength(s)Exposure time criteriaMaximum Permissible Exposure (MPE)Filter characteristics, such as transient bleaching
34MPE Maximum Permissible exposure This is the level of laser radiation that a persons eye or skin may be exposed to without suffering adverse effects.The level is determined by the wavelength, duration of exposure ,the size and divergence of the source
35N.O.H.D. The Nominal Ocular Hazard Distance (NOHD), is the minimum distance from the laser emitter along its optical axis at which no hazard exists to the human eye. An observer at this point or further away would have no adverse eye effects.
36Accessible Emission Accessible Emission This is the level of laser radiation that a person will be exposed to at the closest accessible point of the laser
37EN207 L NumberEN207 L NumberThese numbers are used by laser safety goggle manufactures to specify the level of protection they afford.The numbers define the minimum optical density and the maximum energy or power density that the goggle can withstandOn log scale so L2 10x L1Can also have a prefix specific to type of laser outputreferring to pulse lengths
38Laser classification Divided into the following classes Class 1 Class 2MClass 3RClass 3BClass 4
39Class 1A Class 1 laser is safe for use under all reasonably-anticipated conditions of use; in other words, it is not expected that the MPE can be exceeded. [Comment: This class may include lasers of a higher class whose beams are confined within a suitable enclosure so that access to laser radiation is physically prevented.]
40Class 1MClass 1MClass 1M lasers produce large-diameter beams, or beams that are divergent. The MPE for a Class 1M laser cannot normally be exceeded unless focusing or imaging optics are used to narrow down the beam. If the beam is refocused, the hazard of Class 1M lasers may be increased and the product class may be changed.
41Class 2Class 2A Class 2 laser emits in the visible region. It is presumed that the human blink reflex will be sufficient to prevent damaging exposure, although prolonged viewing may be dangerous.
42Class 2MClass 2MA Class 2M laser emits in the visible region in the form of a large diameter or divergent beam. It is presumed that the human blink reflex will be sufficient to prevent damaging exposure, but if the beam is focused down, damaging levels of radiation may be reached and may lead to a reclassification of the laser.
43Class 3RClass 3RA Class 3R laser is a continuous wave laser which may produce up to five times the emission limit for Class 1 or Class 2 lasers. Although the MPE can be exceeded, the risk of injury is low. The laser can produce no more than 5 mW in the visible region.
44Class 3BA Class 3B laser produces light of an intensity such that the MPE for eye exposure may be exceeded and direct viewing of the beam is potentially serious.CW emission from such lasers at wavelengths above 315nm must not exceed 0.5 watts.
45Class 4Class 4 lasers are of high power (typically up to 500 mW or more if cw, or 10 J cm-2 if pulsed).These are hazardous to view at all times, may cause devastating and permanent eye damage, may have sufficient energy to ignite materials, and may cause significant skin damage.Exposure of the eye or skin to both the direct laser beam and to scattered beams, even those produced by reflection from diffusing surfaces, must be avoided at all times. In addition, they may pose a fire risk and may generate hazardous fumes.
46Laser Safety Department has strict policy which must be compiled with Usage of class 3B and class 4 lasers will be monitored by the Laser Safety Subcommittee via periodic inspections.An internal prohibition notice will be served on any person or Group found to be using lasers in an unsafe manner.The prohibition notice will only be lifted once the control measures described in this document have been fully implemented
47Signage Warning sign on the door of the laser laboratory Should have emergency contactsAll laser users should be namedLaboratory should have door interlocked illuminated signFirst aid advice specific to laser accidents should be displayed in the Laboratory
48Engineering ControlsEngineering controls are measures that are incorporated into the laser system and are designed to prevent injury to personnel. Engineered safety controls are preferable to PPE or Administrative controls.Examples includeProtective housingsInterlocks on Removable protective housingsService access panelsKey control master switch (Class 3B & 4)Viewing Windows, Display Screens, Collecting OpticsBeam path enclosuresRemote interlock connectors (Class 3B & 4)Beam Stop or attenuator (Class 3B & 4)
49Physics Laser safety policy This document contains1. Laser worker registration form,This should be completed by any person whose work involves a class 3b or 4 laser.2. Laser registration form,A separate laser registration form is required for each class 3B or class 4 laser.3. Laser controlled area registration form,Only one laser controlled area registration form is required for each area but the form should be reviewed and updated if necessary whenever a new laser is put into use.4. Pro-forma risk assessment,A risk assessment is required for each experiment making use of class 3B or class 4 lasers it is recommended that separate assessments are carried out for the alignment and normal use stages of the experiment. Unmodified copies of the generic risk assessment are not acceptable5. Pro-forma safe method of work.Each authorised user should sign a copy of the safe method of work
50Laser worker registration form, All persons who intend to work with lasers of Class 3B or above must register as laser workers and sign the declaration that they have read and understood the Local Rules and the University Health and Safety Manual Section L1
51Laser Safety Policy Statement Outline of safety policyRequires that ULSO is notified of all class 3b and 4 lasersLaser supervisors should be familiar with CVCP code of practice and Pd IEC TR :2004AURPO Guidance Note No. 7 “Guidance on the Safe Use of Lasers in Education & Research”.
52Laser Controlled Area Registration form Filled in by laser supervisorCopy available to all laser usersSubmitted to ULSOMust be regularly reviewed
53General risk assessment University risk assessment formCompleted by every laser user with assistance of supervisorForm plus guidance on completion on University H&S website
54Class 3b and 4 laser registration form Filled in by laser supervisorCopy available to all laser usersMpe calculationSafety Co-ordinator has copy of software to perform themSubmitted to LSO
55Safe method of working Guidance on safe working with lasers Requires reading of AURPO Guidance Note No. 7 “Guidance on the Safe Use of Lasers in Education & Research”.Requires viewing of Laser safety in higher educationrequires signature of laser user
56What do with the forms One copy to be retained by laser supervisor One copy of forms to be retained by laser userOne copy to be displayed in relevant laser areaOne copy to be forwarded to Safety Co-ordinator