reported laser accidents in the us from 1964 to 1992€¦ · reported laser accidents in the us...

Radiation hazards - eye damage - skin damage - fire

Non-Radiation hazards - electrical - toxic dyes - toxic gases

Reported laser accidents in the US from 1964 to 1992

High power densities: Thermal, Acoustic (ablation)

Photochemical effects on tissue DNA Damage, Radical formation

Majority of accidents

Risk of irriversible damage

Eye Transmittance

Normal focusing by the eye results in an irradiance amplification of roughly 100,000

Regulated in EN207 & EN208

Maximum Permissible Exposure (MPE) Skin and Eyes (W/cm2 or J/cm2)

Valid for wavelength range: 180 nm – 1 mm

Wavelength (nm)

Power density (W/m2 or J/m2)

Mode of operation (pulsed or CW)

Exposure time

These values are used to determine MPE

500 nm: 385 microwatt for 10 sec. 830 nm: 600 microwatt for 10 sec. 1064 nm: 1.92 milliwatt for 10 sec. 1310 nm: 15 milliwatt for 10 sec.

RISK is different for PULSED LASERS below

55 kHz repetition rate or pulse length

shorter than 100 femtoseconds

Class 1= MPE not exceeded

Class 1M = May be unsafe if optical instruments are used

Class 2= Blink reflex prevents retinal damage

(visible wavelengths)

Class 2M = May be unsafe if optical instruments are used

Class 3B & 3R = MPE is exceeded, dangerous to eyes. Safety goggles are recommended (3B) /compulsory (3R)

Class 4 = (Scattered) radiation is dangerous to eyes and skin. Wear goggles and use screens.

If laser class > 3 wear goggles, use screens!

If laser class > 4 wear goggles, use screens & beam dumps!

Laser goggles are used to decrease exposure.

American standards use optical density

OD =

European regulations are more strict

I

I0log

L-classification (lookup tables)

MPE must not be exceeded

Whole eye must be covered

Goggles must sustain an exposure of 10 seconds or 100 pulses

Wavelength range D = CW operation I,R = Pulsed operation M = Ultrashort pulsed operation L = protection Level

Check Laser class

If laser class >2 use the right goggles

Turn laser sign on

Close door and curtains

Keep laser beam on optical table

Use screens on edge of tables

Use beam dumps for highest powers

Do not change other people’s set up!

Do not remove beam dumps

Do not wear shiny jewelry

Align at low powers

Warn supervisor if you see unsafe behaviour

Let your supervisor and BHV-er know

Seek medical attention

Medication can not reverse retinal damage but reduce damage due to inflammatory response

PhD student was aligning set up in lab

He used glasses

Alignment of an optical isolator

Suddenly he smelt something burning

Holes burnt in on shelf plate

Melted spots marks on laser goggles

1064 nm

3 Watt CW

Beam diameter = 4 mm = 23,9 W/cm2 = 2,39 × 105 W/m2

L scale 5 for 1064 nm operation mode D should be used

L scale 4 was used......

However, back reflected power was found to be 200 mW .... so he was lucky.... Was he?

Goggles OD 1064 nm = 7+

Beam dia < Entrance dia pupil

Exposure on retina = 20nW

MPE Eye = 1.92 mW for > 10 sec

Laser radiation may cause irreversible damage

Know your laser and corresponding goggles

Take care of safety rules

Seek medical attention in case of emergency

Guide to Laser Safety (Laser Vision GmbH)

http://www.noirlaser.com/pdf/net_elements.pdf

http://www.laserlab.vu.nl/en/Images/SAFETY_eyes_tcm116-175360.ppt

j.j.a.weda@vu.nl