1. Safe use of Class 3B and 4 Lasers
Department of Physics
Safe use of Class 3B and 4 Lasers
October 12th 2011
Duncan McCallum
Health and Safety Coordinator

2. Introduction
Introduction to Safe use of Class 3B and 4 Lasers In the Physics department
Departmental Laser safety officer
Prof A.P. Monkman
Health and safety co-ordinator
Duncan McCallum

3. Class 3B and 4 Laser Class 3B and 4 Laser use in Physics
These lasers present a high level of Hazard
Potential of injury to eyes and skin
Eye Damage is usually irreversible

4. Health and Safety
Failure to follow the Universities policies can result in serious consequences in terms of :-
Personal injury to oneself and others
Legal liability for individuals and for the university
In serious cases prosecution by the HSE

5. LASER LASER stands for: Light Amplification by the Stimulated
Emission of
Radiation

6. Lasers Description Lasers can be described by:
which part of the electromagnetic spectrum is represented:
Infrared
Visible Spectrum
Ultraviolet
the length of time the beam is active:
Continuous Wave
Pulsed
Ultra-short Pulsed

7. Synchronous, monochromatic, directional light waves
Laser Light
Laser light
is 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

8. LASER 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 medium
Feedback
mechanism
Output
coupler
Excitation mechanism

9. Laser 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.

10. Electromagnetic Spectrum
Laser wavelengths are usually in the Ultraviolet, Visible or Infrared Regions of the Electromagnetic Spectrum.

11. Common Ultraviolet Lasers
Ultraviolet (UV) radiation ranges from nm. 10
-12
-10 -8 -6 -4 -2 2 4 6 8
x-rays
gamma rays
Ultra-
violet
Infrared
Radar
Radio
waves
Electric
Ionizing
Radiation
Wavelength (cm)
Ultra-
violet
Ultra-
violet
Common Ultraviolet Lasers
Argon fluoride
Krypton chloride
Krypton fluoride
Xenon chloride
Helium cadmium
Nitrogen
Xenon fluoride
193 nm
222 nm
248 nm
308 nm
325 nm
337 nm
351 nm

12. Common Infrared Lasers
Infrared radiation ranges from ,000 nm. 10
-12
-10 -8 -6 -4 -2 2 4 6 8
x-rays
gamma rays
Ultra-
violet
Infrared
Radar
Radio
waves
Electric
Ionizing
Radiation
Wavelength (cm)
Infrared
Infrared
Common Infrared Lasers
Near Infrared
Far Infrared
Ti Sapphire
Helium neon
Nd:YAG
Erbium
Hydrogen fluoride
Carbon dioxide
800 nm
840 nm
1,064 nm
1,150 nm
1,504 nm
2,700 nm
3,390 nm
9,600 nm
10,600 nm

13. Common Visible Light Lasers
Violet
Helium cadmium
441 nm
Blue
Krypton
476 nm
Argon
488 nm
Green
Copper vapor
510 nm
514 nm
528 nm
Frequency doubled Nd YAG
532 nm
Helium neon
543 nm
Yellow
568 nm
570 nm
Rohodamine 6G dye (tunable)
594 nm
Orange
610 nm
Red
Gold vapor
627 nm
633 nm
647 nm
Rohodamine 6G dye
650 nm
Ruby (CrAlO3)
694 nm
The wavelength range for light that is visible to the eye ranges from nm.

14. Leading Causes of Laser Accidents
Unanticipated eye exposure during alignment
Available eye protection not used
Equipment malfunction
Improper methods for handling high voltage (This type of injury has resulted in death.)
Inadequate training
Failure to follow SOP
Failure to provide non-beam hazard protection.
Equipment improperly restored following service
Incorrect eyewear selection and/or eyewear failure

15. BEAM RELATED EFFECTS
Eye related
Eye damage caused by the laser is usually permanent
Skin related
Most skin damage caused by the laser is temporary

16. EYE 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 onto
the retina (dye laser)
- Wavelength - absorbed by different parts of
the eye (CO2 - cornea, sclera)
- duration fraction of second, before you
can blink

17. Eye damage
UV - Cornea + lens
VIS - Retina
IR - Cornea

18. Retinal Hazard Region
The 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.

19. Focusing places the retina at risk

20. Biological 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.

21. Biological Hazards – Cornea & Lens
Ultraviolet and far-infrared laser radiation is absorbed at the cornea or lens
Inflammation 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.
Cornea
Lens

22. Examples of EYE Damage Retinal injury from a dye laser
Corneal injury from CO2 laser
Retinal injury from a dye laser

23. Protect Your Eyes!
In a fraction of a second, your vision can go dark.

24. Types 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

25. Specular 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.

26. Diffuse 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.

27. Biological 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 Injuries
High 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.

28. Non-Beam Hazards
Non-beam hazards refer to anything other than the laser itself that can create a hazard. This type of hazard includes:
Electrical Hazards
Fire Hazards
Laser Generated Air Contaminants (LGAC)
Compressed Gases
Chemical Hazards
Collateral and Plasma Radiation
Noise

29. Non-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.

30. Collateral & 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.

31. Laser 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.

32. Laser 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

33. PPE for Eyes
Personnel 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 eyewear
Laser Power and/or pulse energy
Laser Wavelength(s)
Exposure time criteria
Maximum Permissible Exposure (MPE)
Filter characteristics, such as transient bleaching

34. MPE 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

35. N.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.

36. Accessible 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

37. EN207 L Number
EN207 L Number
These 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 withstand
On log scale so L2 10x L1
Can also have a prefix specific to type of laser output
referring to pulse lengths

38. Laser classification Divided into the following classes Class 1
Class 2M
Class 3R
Class 3B
Class 4

39. Class 1
A 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.]

40. Class 1M
Class 1M
Class 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.

41. Class 2
Class 2
A 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.

42. Class 2M
Class 2M
A 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.

43. Class 3R
Class 3R
A 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.

44. Class 3B
A 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.

45. Class 4
Class 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.

46. Laser 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

47. Signage Warning sign on the door of the laser laboratory
Should have emergency contacts
All laser users should be named
Laboratory should have door interlocked illuminated sign
First aid advice specific to laser accidents should be displayed in the Laboratory

48. Engineering Controls
Engineering 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 include
Protective housings
Interlocks on Removable protective housings
Service access panels
Key control master switch (Class 3B & 4)
Viewing Windows, Display Screens, Collecting Optics
Beam path enclosures
Remote interlock connectors (Class 3B & 4)
Beam Stop or attenuator (Class 3B & 4)

49. Physics Laser safety policy
This document contains
1. 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 acceptable
5. Pro-forma safe method of work.
Each authorised user should sign a copy of the safe method of work

50. Laser 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

51. Laser Safety Policy Statement
Outline of safety policy
Requires that ULSO is notified of all class 3b and 4 lasers
Laser supervisors should be familiar with CVCP code of practice and Pd IEC TR :2004
AURPO Guidance Note No. 7 “Guidance on the Safe Use of Lasers in Education & Research”.

52. Laser Controlled Area Registration form
Filled in by laser supervisor
Copy available to all laser users
Submitted to ULSO
Must be regularly reviewed

53. General risk assessment
University risk assessment form
Completed by every laser user with assistance of supervisor
Form plus guidance on completion on University H&S website

54. Class 3b and 4 laser registration form
Filled in by laser supervisor
Copy available to all laser users
Mpe calculation
Safety Co-ordinator has copy of software to perform them
Submitted to LSO

55. Safe 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 education
requires signature of laser user

56. What do with the forms One copy to be retained by laser supervisor
One copy of forms to be retained by laser user
One copy to be displayed in relevant laser area
One copy to be forwarded to Safety Co-ordinator