Lasers

Question 1

Class 1

Answer 1

No risk to skin and eyes
Safe for long-term intra-beam viewing
Completely enclosed
Examples: DVD player, laser cutting system

Question 2

Class 1M

Answer 2

No risk to skin and eyes
Safe for long-term intra-beam viewing
Hazardous if viewed with magnifying optics
Examples: laser diodes, speed meters

caution warning

Question 3

Class 1C

Answer 3

No risk to eye if laser remains in contact with tissue
AEL stopped or reduced below AEL of Class 1
Example: at home laser hair removal

follow instructions for use labelling

Question 4

Class 2

Answer 4

Visible beams
No skin risk
Safe for momentary intra-beam viewing and with optical instruments
Hazardous for deliberate viewing
Blink response/ head movement
Example: laser pointer

do not stare labelling

Question 5

Class 2M

Answer 5

Visible beams
No skin risk
No risk to eye for short intra-beam viewing
Blink response/ head movement
Possible eye injury using viewing instruments
Example: alignment laser for CT

yellow caution label

Question 6

Class 3R

Answer 6

Low risk to eyes for intentional viewing
No risk to skin
Professional use
Example: alignment or levelling lasers

Question 7

Class 3B

Answer 7

Risk to eyes from intra-beam viewing
Diffuse viewing is safe
Low risk to skin
Examples: physiotherapy, broadband sources

amber warning label

Question 8

Class 4

Answer 8

High risk to eye for both direct and diffuse viewing
High risk to skin
Fire hazard
Examples: surgical lasers, cutting

red danger labelling

Question 9

Components of Laser Eyewear Marking Scheme

Answer 9

1064 D LB7 X CE95
1. Wavelength range
2. Test condition
3. Protection factor
4. Approve inspection body test mark
5. Conformity test mark

Question 10

Test conditions for laser eyewear marking scheme

Answer 10

D = continuous wave
I = long pulsed
R = Q-switched
M = Mode-locked

Question 11

Two main laser safety regulations

Answer 11

Control of Artificial Optical Radiation at Work Regulations
Artificial Optical Radiation Directive

Health and Safety at Work Act is also relavent

Question 12

Aim of laser standards

Answer 12

to ensure consistency in manufacturing or a particular task

IEC (International Electrotechnical Comission)

Question 13

What are laser classifications based on?

Answer 13

1. eye and skin risks
2. conditions of use, exposure time or environment
3. accessible emission limits (AEL)
4. maximum permissible exposure (MPE)
5. worst case assumptions

can be used as a guide for a risk assessment

Question 14

What is accessible emission?

Answer 14

The power or energy of radiation emitted by the laser that is accessible.
Is compared to the AEL under various standard conditions.

Question 15

What are the conditions under which AEL values are compared?

Answer 15

Timeframe
Limiting aperture
Distance
Source size

Question 16

What is the time basis of 0.25s used for?

Answer 16

Class 2, 2M and 3R
400-700 nm

Blink response

Question 17

What is the time basis of 100s used for?

Answer 17

all wavelengths greater than 400nm

aversion response

Question 18

What is the time basis of 30,000s used for?

Answer 18

all wavelengths <= 400 nm
all wavelenghts > 400 nm where intentional long term viewing is inherent

working day

Question 19

What is the retinal hazard region?

Answer 19

400 - 1400 nm

Question 20

What are the manufacturer safety requirements for class 3B/4 lasers?

Answer 20

remote interlock
emission warning
beam stop
key-switch
safety docs
aiming beam
NOHD
audible or visible beam on indicator
eye protection

Question 21

What are the manufacturer safety requirements for all classes except 1?

Answer 21

safety lables
aperture marked

Question 22

What does the Control of Artificial Optical Radiation at Work Regs require employers to do?

Answer 22

assess the risk of adverse health effects to the eyes and skin
eliminate or reduce risks below Exposure Limit Values
inform and train staff
provide health surveillance and medical examinations

Question 23

What is the manufacturing standard and what does it cover?

Answer 23

BS EN 60601
basic safety and essential preformance
electrical safety, voltage, graphic symbols, safety measures
covers class 3B and 4 lasers

Question 24

What is the safety standard and what does it cover?

Answer 24

BS EN 60825
safety measures, wavelengths, marking, physilogical effects
laser guards
safe use of lasers on humans (class 1C, 3B, 4)
guidance for best practice (MPE, NOHD)
eye protection
surgical drapes

Question 25

Maximum Permissible Exposure

Answer 25

highest power or energy density of a source that is considered safe (J/m^2 or W/m^2)

depends on wavelength, exposure time, observation geometry

Question 26

5 steps of a risk assessment

Answer 26

1. Identify Hazard
2. Identify who may be harmed and how
3. Evaluate risks and decide on control measures
4. Record findings and implement them
5. Review and update if necessary

Question 27

What are the hazards relating to the use of lasers?

Answer 27

1. Equipment (fire, trip hazard)
2. Process (plume, internal fire)
3. Environment (controlled area, reflections, interlocks)
4. Personnel (staff, patient)

Question 28

What is the Nominal Ocular Hazard Distance?

Answer 28

distance at which the beam irradiance or radiance exposure = MPE

Question 29

What is the heirarchy of controls?

Answer 29

1. Elimination
2. Substitution
3. Engineering Controls
4. Administrative Controls
5. PPE

Question 30

Who are the duty holders?

Answer 30

LPS
Clinical Laser Expert
LPA
LSO

Question 31

When are local rules required?

Answer 31

for every class 3B and 4 laser

MHRA provides guidance on what should be included