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Laser Safety Awareness
Health, Safety and Wellbeing
Rob Powell – HSW Manager
• Justification
• Lasers and eyes
• Laser accidents
• Laser classes
• Accident prevention
• Responsibilities
Agenda
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• The University of Auckland is responsible for the health and safety of its staff, students and visitors whilst working and studying.
• High powered lasers are capable of causing permanent damage and training is an essential risk control.
• Laser safety awareness (this lecture) is the minimum level of competency required to work with high powered lasers (under supervision).
Justification
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• Note: Laser pointers in excess of 1mW are prohibited weapons in Australia, and cannot be imported into New Zealand.
• There are severe penalties for using laser pointers to dazzle drivers and pilots.
Introductory Video
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https://www.youtube.com/watch?v=EnKxKmaJvfY
Anatomy of the eye
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macula: allows for colour vision
fovea: central spot of macula allowing for sharp central vision (such as
reading, watching TV, driving, and all other visually reliant activities)
Sun vs 1mW Laser Pointer
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• Energy from direct Sunlight (Don’t look at the Sun, you’ll burn your eyes out)Maximum intensity of sunlight at ground level (directly overhead, no smog, etc.) = 1 kW/m2 or 1 mW/mm2.
Assuming pupil diameter is 2 mm (i.e., radius of 1 mm), the area is approximately 3 mm2. So, the power of the sunlight through the pupil = 3 mW.
Focal length of eye's lens = approximately 22 mm. Angular size of Sun from Earth = 0.5 degree = 9 mR.Thus, diameter of image formed = 22 mm x 9 mR = 0.2 mm and the area of image = 0.03 mm2.
The intensity of the Sun on the retina (Power/Area) = 3 mW/0.03 mm2
=100 mW/mm2.
• Energy from a typical 1 mW laser pointer (It’s just a little laser pointer)Power (P) = 1 mW, wavelength (l) = 633 nm, radius of beam (w) = 1 mm, focal length of eye (f) = 22 mm. So, the diameter of spot = (2 x f x l)/(w x pi) = 9 x 10-3 mm and the area of spot = 6 x 10-5 mm2.
The power density of the laser on the retina is 1 mW/(6 x 10-5 mm2) = 16,667 mW/mm2
=16.667 watts/mm2.
Sun vs 1mW Laser Pointer
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• Because laser light is collimated, the 1 mW laser has the potential to produce an intensity on the retina 167 times that of viewing direct sunlight.
• How much more powerful is a 5W laser?
Light transmission through the eye depends on Wavelength
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Sensitivity to Damage: Energy Transmission
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Methods of Viewing
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Hazards associated with laser use
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• Beam hazards
– eye damage
– skin damage
• Non-beam hazards
– electrical hazards
– hazardous gases and fumes from ablated material
– fire
Types of laser incidents
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Summary of reported laser incidents in the United States from 1964 to 1992 (percentages)
Primary causes of accidents
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Summary of reported laser incidents in the United States from 1964 to 1992 (percentages)
Examples of Laser Accidents
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Note: 2 photos of damaged Retinas feature in this section
Reflected beam caused vision loss
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China:
A professor removed his eyewear to "see better" while doing an experiment with a crystal.
Exposure produced retinal burn and permanent vision loss.
He described seeing a white flash and a central purple spot surrounded by yellow halo. No pain reported.
Blurred vision from reflected exposure.
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USA:
A student received a reflected beam from plastic tool box lid.
No eye protection was worn, and the student had not received laser safety training.
Student reported blurred vision and seeing black spots. After one month, the student still had blurry vision.
Party laser blinds Russian ravers
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Dozens of partygoers at an outdoor rave near Moscow have been partially blinded after a laser light show burned their retinas, say Russian health officials.
"They all have retinal burns, scarring is visible on them. Loss of vision in individual cases is as high as 80%, and regaining it is already impossible," a treating ophthalmologist says.
"I immediately had a spot like when you stare into the sun," said attendee Dmitry.
Example of eye injury
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Retinal Burns
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The white spots in the centre are thermal burns. With larger energies, holes and bleeding in the retina are produced from small steam explosions generated within the eye fluid.Photograph courtesy of J. Zuclich, TASC Litton, TX, USA.
Eye damage effects
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Actions on eye injury or suspected eye injury
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• Experience has shown that most laser injuries go unreported for 24 - 48 hours by the injured person. This is a critical time for treatment of the injury.
• Shut down the laser and tell your supervisor.
• Quarantine the area and equipment for investigation.
• Cover the injured eye and protect from light.
• Report to a medical centre without delay.
• Contact the Health, Safety and Wellbeing Service on ext 84896 and inform them of the incident.
Laser Classes
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Class 1 and 1M Lasers
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• Class 1 lasers. Not capable of producing damaging radiation levels during normal operation. Low powered exposed lasers or higher powered lasers embedded within instruments or machines that totally enclose the beam.
• Class 1M lasers. Not capable of producing damaging radiation levels to the unaided eye, but may cause damage when direct intrabeam exposure occurs using magnifying optics.
Class 2 and 2M lasers(low power)
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• Class 2 lasers emit visible light. Skin safe, but may cause eye damage when direct intrabeam exposure occurs for more than 0.25 second (natural aversion response).
• Class 2M lasers emit visible light. Skin safe, but may cause eye damage when direct intrabeam exposure occurs for more than 0.25 second (natural aversion response). May cause eye damage when direct intrabeam exposure occurs using magnifying optics.
Class 3R and 3B lasers (medium power)
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• Class 3R lasers emit visible and invisible light. Skin safe, but may cause eye damage when direct intrabeam exposure occurs.
• Class 3B lasers emit visible and invisible light. May cause skin damage, but likely to cause eye damage when direct intrabeam exposure occurs. Viewing diffuse reflections is normally safe.
Class 4 lasers (high power)
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• Hazardous under all viewing conditions: direct, specular and diffuse.
• Hazardous to skin.
• Potential fire hazard when in contact with combustible materials.
• Can produce laser generated air contaminants and hazardous plasma radiation.
• Extreme caution and additional controls required.
Laser Accident Prevention
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Use a lower powered laser if possible.
Use remote viewing methods (e.g. video) if possible.
Wear the correct laser protective eyewear.
Do not wear watches and reflective jewellery.
Laser operators must know how to operate the laser.
Never work alone.
Restrict unauthorised access to the laser control area.
Arming keys are to be under positive control.
Don’t route beams at eye level (standing or sitting).
Responsibilities
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The University is responsible for the safety of its staff and students, and exercises its responsibility by providing policy, guidelines and periodic control by designated safety personnel.
www.auckland.ac.nz/hsw > Hazards > Laser Use Policy
We are all personally responsible for our own health and safety, and that of others who may be affected by our work, research or study, and our acts and omissions.
Acknowledgements / References
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• This presentation is inspired by a similar presentation on Laser Safety by the Molecular & Laser Physics Group of the Radboud University, Nijmegen NL.
• Further information from Fred Seeber, Camden County College, Blackwood, New Jersey
• Laser incidents taken from laser accident database of Rockwell Laser Industries, Inc. and
• Certain descriptions and numbers are taken from the international standard: AS/NZS IEC 60825-14:2001.
Recap
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• Justification
• Lasers and eyes
• Laser accidents
• Laser classes
• Accident prevention
• Responsibilities
