- 11 -
1. LASER SAFETY
1.1. LASER TYPES
There are different types of lasers according to the medium of photon propagation (gas, solid, liquid, etc.)
contained inside the laser tube and the excitation mechanism used to cause the laser process. As a result,
laser emissions of different wavelengths (energy content and power) are obtained. The risks from
exposure to laser emission are different for each type of laser. According to the features mentioned above,
lasers are categorized into 4 classes and their Accessible Emission Limit (AEL) is specified as follows
:
•
Class I
.
Lasers that are safe under reasonably foreseeable conditions of operation, including the use of
optical instruments for intrabeam viewing.
•
Class IM
.
Lasers emitting in the wavelength range from 302.5 nm to 4000 nm which are safe under reasonably
foreseeable conditions of operation, but may be hazardous if the user employs optics within the
beam. Two conditions apply:
a) for diverging beams if the user places optical components within 100 mm from the source to
concentrate (collimate) the beam; or
b) for a collimated beam with a diameter larger than the diameter specified in table 10 for the
measurements of irradiance and radiant exposure.
•
Class II
.
Lasers that emit visible radiation in the wavelength range from 400 nm to 700 nm where eye
protection is normally afforded by aversion responses, including the blink reflex. This reaction may
be expected to provide adequate protection under reasonably foreseeable conditions of operation
including the use of optical instruments for intrabeam viewing.
•
Class IIM
.
Lasers that emit visible radiation in the wavelength range from 400 nm to 700 nm where eye
protection is normally afforded by aversion responses including the blink reflex. However, viewing of
the output may be more hazardous if the user employs optics within the beam. Two conditions apply:
a) for diverging beams, if the user places optical components within 100 mm from the source to
concentrate (collimate) the beam, or
b) for a collimated beam with a diameter larger than the diameter specified in table 10 for the
measurements of irradiance and radiant exposure.
•
Class IIIR
.
Lasers that emit in the wavelength range from 302.5 nm to 106 nm where direct intrabeam viewing
is potentially hazardous but the risk is lower than for Class 3B lasers, and fewer manufacturing
requirements and control measures for the user apply than for Class 3B lasers. The accessible
emission limit is within five times the AEL of Class 2 in the wavelength range from 400 nm to 700 nm
and within five times the AEL of Class 1 for other wavelengths.
•
Class IIIB
.
Lasers those are normally hazardous when direct intrabeam exposure occurs (i.e. within the NOHD).
Viewing diffuse reflections is normally safe.
•
Class IV
.
Lasers those are also capable of producing hazardous diffuse reflections. They may cause skin
injuries and could also constitute a fire hazard. Their use requires extreme caution.
