Laser Safety

Question 1

Describe the difference in laser classes and how are they classified?

Answer 1

Classified by Accessible Emission Limit - requires wavelength, exposure duration, viewing conditions

Class 1: Safe - no hazard to eyes or skin

Class 2: Safe to skin, hazard to eyes if t >0.25s

Class 3B: Safe to skin, not eye safe for direct viewing, may be okay for diffuse beams, if t >0.25s, max 0.5W.

Class 3R: Safe to skin, not eye safe for viewing through binoculars, telescopes etc. Max 5mW AND irradiance <25W/m2.

Class 4: Not safe for skin or eyes eg. CO2, Nd:YAG

Question 2

Where do the different types of UV affect the eye?

Answer 2

UV-A - lens
UV-B - absorbed by cornea
UV-C - affects surface of cornea

Question 3

Where do the different types of infrared radiation affect the eye?

Answer 3

IR-A - retina
IR-B - absorbed by cornea and penetrates aqueous humor
IR-C - absorbed by cornea

Question 4

Where do different radiation levels penetrate the skin to?

Answer 4

IR-B/C - stopped by epidermis
UV - epidermis and stopped by dermis
Visible - epidermis, dermis and stopped by subcutaneous
IR-A - through them all

Question 5

What is the MPE for skin?

Answer 5

Same as sunlight - 1000W/m2

Question 6

How do we categorise laser safety?

Answer 6

Process, Beam Delivery, Laser, Environment and People

Question 7

Where are different particle sizes stopped in the body when inhaled?

Answer 7

7-50um: filtered by nose
5-7um: deposits are coughed out or swallowed on mucus
0.1-7um: causes harm to respiratory system, biggest hazard
<0.5um: essentially gases so exhaled

Question 8

Where should fume extraction be?

Answer 8

At point of generation

Question 9

What is the hierarchy of controls to reduce radiation exposure?

Answer 9

Engineering Controls - housing, enclosures, interlocks (fail to safe), beam stops, filtered windows, control of beam path, key switches (required for 3B and 4 lasers)

Administrative Controls - Written Safety Instructions (WSI), appointment of a Laser Safety Officer (LSO), risk assessment, warning signs, education and training

PPE - goggles, protective clothing

Question 10

What is the difference between active and proactive control to laser safety?

Answer 10

Active or Reactive systems respond after a laser beam has escaped and cuts off.

Proactive systems can anticipate and detect fault conditions.