There are four Classification of lasers as follows:
Class 1 classification of lasers
The output power of this laser is measured in tenths of milli watts. Under standard conditions of operation, they do not create a health hazard.
Generally these devices are totally enclosed. Hence, the beam does not exit the housing. A CD player is an example of class I laser.
Class 2 classification of lasers
Lasers in this category emit only visible light with low power output. These lasers also normally do not cause a health hazard.
There are two subclasses of Class 2 lasers:
(a) Class 2 a: when directly viewed for longer than one thousand seconds it is hazardous.
(b) Class 2 b: has a dangerous viewing time of one fourth of a second. This is the length of time of an ordinary blinking reflex.
Small laser pointers and supermarket bar code scanner belong to Class 2 lasers.
Class 3 classification of lasers
These types of lasers also have two subclasses as follows:
(a) Class 3 a and
(b) Class 3 b.
(a) Class 3 a: They can emanate any wavelength. These lasers have a forewarning label on them. In this class, when the laser light is viewed only momentarily, i.e., one-fourth of a second- blinking reflex, it may not damage the unguarded eyes.
(b) Class 3 b: Class 3 b lasers will not cause reflective hazards when using, not shiny but matted surfaces. Normally do not produce fire hazards. They have dental treatment time measured in minutes. Hence, eye protection becomes mandatory to use. They can create a hazard to unguarded eyes if inspected directly or viewed from reflective light for any length of period.
Low-level therapeutic lasers (LLL) belong to be class 3 a or class 3 b classification of lasers, depending on the emission wavelength and duration of exposure.
The lasers presently used in dentistry are class 3 b or class 4.
Class 4 Lasers classification of lasers
This category of lasers is hazardous from direct viewing and may produce hazardous diffuse reflections. Moreover, they also present the possibility of serious eye and skin damage. These devices also produce fire and skin hazards. Appropriate laser safety glasses for the wavelength used must be worn while the laser is on.