Transcript Kein Folientitel - Bernd Michael Fischer

Laser safety Introduction
B. Fischer
T-ray group meeting 08/06/06
08/06/2006
Laser safety
1
Motivation
 It might appear unnecessary
 Our lab is safer than most other T-ray lab in the world
but:
 Regular training is required by law
 Initial laser training for new staff
 Gives you the opportunity to become aware again of some issue
 Possibility to reflect on your practice
finally: You have only two eyes !
source: http://www.adrenotex.de/augenklappe.htm 2
In older times
Why do pirates
wear patches?
navigators had to stare into
the sun if using a sextant
intense light damages your eyes!
sources: http://en.wikipedia.org/; http://www.stuckiag.ch/shop/de-ch/dept_380.html
3
Eye damage – 400-1400 nm
Visible and near-infrared light enters
the eye and is focused tightly on the
retina (10-25 mm diam).
even in VIS, only about
5% will be absorbed in
visual pigments
retinal burn: (irreparable) damage
cw and long-pulse lasers: mainly thermal, 400-600 nm also photochemical
4
Eye damage – 315-390 nm
Light penetrates to the lens and can cause damage here
(photochemical cataract)
5
Eye damage – 180-315nm and >1400nm
light stopped by the cornea
photokeratitis, corneal burns (similar to sunburns)
(1.5 mm – 2.6 mm light penetrates in aqueous humour, large volume, rather eye-safe)
6
Laser safety – other hazards
•
Skin exposure
– Particularly high power and/or UV lasers
•
Fire hazard
– Beams hitting flammable materials
•
Electrical shocks
– Gas discharge lasers can operate with high voltage (kV) and high currents
(50-100 A)
•
Chemical hazards
– Toxic laser materials
• Dyes and solvents
• Chemical lasers
there is a general understanding that
accidents of this kind greatly
outnumber eye strikes
7
Laser safety legislation
•
Legal Responsibilities – for employer & employee

Occupational Health & Safety at Work Act

Work Equipment Regulations

Management Regulations – risk assessments
8
Australian Standards
9
European Health & Safety Law
• Health & Safety at Work Act



The act places duties on both employers and employees
It is criminal law and can be enforced against criminals and
organisations
The act can be summed up as;
 Employers duty: ‘To safeguard so far as reasonably practicable
the health, safety and welfare of employees and others affected
by the work’.
 Employees duty: ‘To take reasonable care for the safety of
themselves and others; to cooperate; not to be reckless’
10
Typical Work Equipment Regulations

All equipment must be suitable

Maintained in an efficient state

Maintenance recorded

Restricted to trained users

Users must have information and training

Access prevented to dangerous parts

Adequate controls and lock-offs

Suitable environment
11
European standards on laser safety
 deals with lasers and laser products,
i.e. product or assembly of components which contain lasers or laser systems
 E.g. compact disc players
 includes also light emitting diodes (LEDs)
(modern LEDs are high-power, highly directional light sources)
 indicates safe working level for laser radiation
 classification of lasers & laser products according to degree of hazard
 labeling  warnings
 minimize accessible radiation, control measures
 protection against non-radiation hazards associated with lasers
12
Reasoning behind classification
• Classification of laser determined by:
 Accessible Emission Limit (AEL)
Maximum level of laser radiation accessible over its full range of
capability during operation at any time after its manufacture
• To classify a laser, you need to know:
 Laser wavelength
 Exposure duration
 Viewing conditions
• Each laser class has a set of safety control measures that manufacturers and
users must obey
• Manufacturers should supply this classification
(attention: slight differences between USA and Europe -> Australia?)
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Laser classification
Class 1
Safe under reasonably foreseeable operation
Class 1M
Generally safe – some precautions may be required
Class 2
Visible light at low power, blink limits risk
Class 2M
Visible light at low power, generally safe – some
precautions may be required
Class 3R
“Low” risk for direct viewing of beam
Class 3B
Viewing beam hazardous, diffuse reflections safe
Class 4
Hazardous under all conditions, eyes and skin
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Class 1 (safe)

Safe under reasonably foreseeable conditions of operation, including the use of
optical instruments for intra-beam viewing

rather complex calculation, but rule of thumb for cw lasers
VIS (400-700):
0.39 mW
NIR/IR (700-1400):
slowly increasing, e.g. 1.6 mW for 1 mm
MIR (1.4 –4 mm)
10 mW (“eye-safe” communication)
FIR (> 4 mm)
1000 W/m2
measurement area: normally iris with diameter 7 mm


A product may contain high power laser with higher classification, if
effective engineering controls restrict routine exposure to Class 1 AEL
• CD, laser printers
• possibly machining, etc.
• in lab: cleverly set up spectrometer (?)
15
Class 1M

New class, mainly for EN60825-2 regulations to deal with
fibres (communications) & LEDs

Wavelength range  302.5 nm to 4 mm

Generally these lasers are as “safe” as Class 1

Except for diverging or large area beams when collecting optics
used
 These large beams may be focused to a spot of sufficient
intensity to cause damage to the retina
16
Class 2 (low power)

Max output – 1 mW

Visible only: 400 nm to 700 nm

Blink response of eye affords protection (0.25 s)

E.g:

Supermarket scanner

many HeNe laser, some laser diodes

legal laser pointers

note: recent research questions reliability of blink reflex
consider also fatigue, alcohol, drugs, ...

Class 2M divergent or broad-aperture sources, which meet Class 2 standard
without additional optics

OK if collecting optics not used
17
Class 3R (low to medium power)

Direct intrabeam viewing is hazardous, but risk is lower than for 3B

wavelength > 302 nm

maximum AEL 400-700 nm = 5 times AEL of class 2, i.e. 5 mW

maximum AEL at other l

E.g:

= 5 times AEL of class 1

Surveying equipment

many laser pointers

Some HeNe and laser diodes in teaching & research labs
there is no class 3A anymore
18
Class 3B (medium power)

Max output - 0.5W (500 mW)

Includes all visible and non-visible lasers

Direct intrabeam viewing is always hazardous

Viewing diffuse reflections is normally safe provided:
 Eye is not closer than 13 cm from diffusing surface
 Exposure duration is less than 10 seconds

e.g.
•
many laser diodes
•
small solid-state lasers
•
small ion lasers
19
Class 4 (high power)

> 500 mW

capable of producing hazardous diffuse reflections

capable of producing also skin burns and fire hazards

e.g.
• most solid-state lasers
• laser diode bars, some single emitters
• most ion lasers
20
(Repetitively) Pulsed lasers
 exposure from any single pulse shall not exceed AEL for single pulse
AEL depends on pulse duration, wavelength, ...
 average power of a pulse train of duration T shall not exceed the AEL for a
single pulse of duration T
 for wavelength larger than 400 nm (thermal limits):
average pulse energy shall not exceed single pulse AEL times correction factor
AE train = AELsingle N–0.25
N number of pulses
(by the way, there are more details to it)
21
Consequences
• appointment of laser protection officer (invisible class 3R, 3B, 4)
• labelling
• training (class 1M, 2M, 3R, 3B, 4)
• protective enclosures where applicable, access restrictions
•interlocks (class 3B and 4)
22
Labelling

Labels for laser user & laser servicer

Correct labels should be provided by manufacturer

If size or design of laser makes labeling impractical (e.g. laser diode),
put it on the mount or base.
(only in rarest circumstances labels should be included only with user
information or placed on package)

Laser starburst warning label
on all laser products of Class 2 and above

Access panels, Safety interlocked panels
Should be labeled if access to laser radiation in excess of the AEL
for Class 1/1M is possible on their removal or over-riding
source: http://www.lasermet.com/labels/labels-updated.html
23
Labelling II
 every laser needs a label with warning level increasing with class
e.g. class 2
 e.g. class 3R
 lasers of class 3R, 3B, 4 need labelling of aperture
 if radiation is outside the 400-700 nm range, “laser radiation” needs to be
replaced by “invisible laser radiation” or “visible and invisible laser radiation”
source: http://www.lasermet.com/labels/labels-updated.html
24
MaiTai -> Class 4 laser
25
Laser safety – University policy
 Appointed Laser Safety Officer (LSO)
 All lasers (3R, 3B, 4) must be registered(?)
 All lasers and users conform to Australian Regulations
 Risk assessment & safe method of work completed at workplace
 All laser users must attend risk assessment & safe method of work briefing
 The supervisor (Bernd or Tamath) overseeing the laser project must
ensure safe working practices as followed
26
Practical laser safety
There is a hierarchy of controls to ensure the safe use of lasers:
•
Risk Assessment and Safe Method of Work
 (1) Engineering controls
 (2) Administrative controls
 (3) Personal protective equipment (PPE)
27
Engineering controls
To Restrict exposure to laser radiation use:


Housings
Enclosures
 Put the laser in a box if applicable
 Use tubing on (long) laser runs
Advantage: improves stability and reduces contamination
Disavantage: Not applicable in laminar flow conditions



Beam stops
Interlocks
Warning lights
 Block beams as soon as is possible
 Prevent unauthorised access to danger
 Informs others of the possible danger
 remote sensing  align beams without danger
28
Engineering controls II
Controls should not be over restrictive and hamper ease of working
but also:
Never bodge and no temporary fixes
It compromises safety
29
Administrative controls
But: Engineering controls may not provide adequate protection in
cases such as:

Phases of research when laser system is being commissioned

Servicing of laser equipment

Manufacture or research into laser design

Laser alignment

Special projects: waveguides, near-field, dynamis

In these situations:
so essentially in
many, but not all
situations we are
working in
Use Administrative controls to minimise risk
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T-ray labs around the world
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It’s also about communication
Clear instructions?
Clearly understood?!
Actually, your colleagues in the lab are
often more at risk, if you do something
dodgy, than you are, because they do
not know that you are going to do it.
32
Examples for administrative controls
Warning Signs & Notices Prominently displayed – clear and unambiguous
 Labels at entrances to lab or workshop containing Class 3B or 4 laser
Laser Controlled Area (Class 3B or 4 laser)
Restricted to authorized persons
By physical means: walls & doors, Locks or number pads
Key Control
Class 3B & 4 laser keys removed when not in use
Kept secure in key cabinet to which authorized users only have access
Training
 Only trained persons allowed to use 1M, 2M, 3R and the more 3B and 4 lasers
Maintenance & Service Manuals
Must be available and easily accessible to laser users
33
Personal protective equipment (PPE)
Used only when:
 Risk of injury or harm can not be suitably minimised by engineering controls etc

Laser safety goggles
• required for Class 3R outside of 400-700 nm window, 3B and 4
• saves us in teaching labs, if everything else is ok, i.e. direct beam
viewing is not possible due to engineering controls

Fire resistant clothing, gloves, overalls
• against hazards associated with lasers (noise, chemical etc)
• Protective clothing when exposure to radiation exceeding maximum
permissible exposure for skin (MPE), i.e. possibly strong class 4 lasers

use during
• alignment or open beam experiments
•
maintenance and servicing
Employers are obliged to
provide employees with PPE!
34
Goggles

Purpose: to reduce level of incident laser radiation upon cornea to below MPE
maximum permissible exposure,
essentially: make it a class 1 laser!

Filter: Sufficient optical density (OD) to attenuate incident radiation to MPE
rule of thumb 0.4 mW – some mWs, but check your wavelength and conditions
(OD of 5 means that a filter transmits less than a part in 105 at that wavelength)

Legal requirement to comply with:
 Personal Protective Equipment Product Directive (89/686/EEC) July 1995
 European Standards;
 EN207:1998 Filters & equipment used for personal eye protection against
laser radiation
 EN208: 1999 Personal eye-protectors used for adjustment work on lasers
and laser systems
VIS, 400 – 700 nm, attenuation to < 1 mW
35
Markings on goggles
In order to meet legal requirements, the goggles need to be marked with

Wavelength or wavelength range in nm against which protection is afforded

Scale No or lowest scale No if protection against a spectral range is afforded

The manufacturers identification mark

Test mark of the inspection body (CE or possibly DIN for rather old goggles)
scale number
corresponds to
optical density
Marking with OD alone is NOT sufficient ! The scale number confirms that the
filter withstands at least 10 s and that also the frame does not disintegrate
36
Frames of goggles
high safety
(TOPS)
ok
possibly weak
points at side
balance between optimal safety and acceptance by the user
(what happens with prescription glasses?)
sources: Lasermet, Laservison
37
Practical laser safety again
If you do not find
at least eight
safety flaws in
here contact me
(discreetly)
wrong
brand?
38