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Laser Classification

Lasers are grouped into seven classes depending on the potential for the beam to cause harm. The hazard and hence the classification depends on the wavelength, power, energy and pulse characteristics. The class of the laser can be used to help decide what safety control measures are required when using the laser. The Accessible Emission Limit (AEL) is the maximum level of laser radiation which a laser can emit (and be accessible) at any time after its manufacture. The AEL depends on the wavelength, exposure duration and the viewing conditions and specifies the maximum output within each laser class.

A distinction should be made between a laser system (which refers to the laser and appropriate energy source) and a laser product (which is defined as "any product or assembly of components which constitutes, incorporates or is intended to incorporate a laser or laser system, and which is not sold to another manufacturer for use as a component (or replacement for such component) of an electronic product"). For example a CD player is a laser product which contains a laser system – the laser diode and power supply. It is the laser product which is placed into one of the seven classes. (The laser product may only consist of a laser system, e.g. a HeNe laser). The descriptions which follow give a summary of the laser classifications.

Class Basis for Classification
Class 1 Laser Inherently Safe   Visible/non visible Lasers which are safe under reasonably foreseeable conditions of operation.
Class 1 Laser product Safe as long as not modified A product that contains a higher class laser system but access to the beam is controlled by engineering means.
Class 2 Low Power Visible only For lasers, protection of the eyes normally provided by natural aversion blink response which takes approx. 0.25s. Theses lasers are not intrinsically safe. AEL = 1 mW for a CW laser
Class 1M   Safe without viewing aids   302.5 to 4000nm Safe under reasonably foreseeable conditions of operation. Beams are either highly divergent or collimated but with a large diameter. May be hazardous if user employs optics with the beam.
Class 2M   Safe without viewing aids   Visible only Protection of the eyes is normally provided by natural aversion blink response which takes approx. 0.25s. Beams are either highly divergent or collimated but with a large diameter. May be hazardous if user employs optics with the beam.
Class 3R   Low/medium power   Visible / non-visible Risk of injury is greater than for the lower classes but not as high as for class 3B. Up to 5 times the AEL for Class 1 and Class 2.
Class 3B   Medium / high power Visible / non-visible Direct intrabeam viewing of these devices is always hazardous. Viewing diffuse reflections is normally safe provided the eye is no closer than 13 cm from the diffusing surface and the exposure duration is less than 10 seconds. AEL = 500mW for a CW laser
Class 4   High power Visible / non-visible Direct intrabeam viewing is dangerous. Specular and diffuse reflections are hazardous. Eye, skin and fire hazard. TREAT CLASS 4 WITH CAUTION
















The following labels are associated with the different classes of lasers

The points of access to areas in which Class 3B or Class 4 lasers are used must be marked with warning signs complying with BS 5378 and the Health & Safety (Safety Signs and Signals) Regulations 1996. The following sign must be used:

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Where lasers and laser systems are not adequately labelled (e.g. some American systems have very small labels that are hard to read and do not comply with UK requirements), they must be properly relabelled.

Class 1

Class 1 lasers and laser products are inherently safe under reasonably foreseeable conditions of operation including the use of optical instruments for intra-beam viewing and as such they present no hazard to the eye or skin. They can emit in the visible or invisible. A class 1 laser product may contain a laser system of higher classification, but the engineering controls keep the AEL below the class 1 limit for example a CD/DVD player or a laser printer.

Inherently safe lasers in Class 1 do not need warning labels but lasers which are Class 1 by engineering design and which contain an embedded laser of higher power should be labelled as 'Class 1 Laser Product’. Supplementary information describing the laser product as a ‘Totally Enclosed System' with details of the embedded laser clearly displayed may be of value in situation where access to the embedded product is routinely required.

class1


In addition each access panel or protective housing must have a label with the appropriate class inserted and then followed by the hazard warning associated with that class of laser (see warning statements in following labels).

caution

Class 1M (safe if not using viewing aids).

Class 1M lasers are restricted to 302.5 to 4000nm. They are safe under reasonably foreseeable conditions of operation but may be hazardous if observed using viewing optics. They can be hazardous under two conditions:

a) If the beam is diverging and optics are used within 100mm of the laser aperture to collimate or concentrate the beam into the eye, or

b) If the beam is a large diameter and collimated and optics are used to increase the proportion of the beam that can enter the eye.

Example: Laser diode, LED, fibre communications system.

No hazard warning label is required but there must be an explanatory label bearing the words:

class1m

Class 2 (low power)

Class 2 only applies to lasers emitting in the visible region, 400 to 700nm. They may be pulsed or continuous wave. Protection of the eyes is normally provided by the aversion response (blinking and/or moving the head) and therefore it is assumed that the exposure time is 0.25s. The AEL for a CW class 2 laser is 1mW.

Example: Alignment HeNe lasers with powers below 1mW, supermarket bar scanners.

A label with hazard warning symbol and an explanatory label as below are required:-

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Class 2M

Like class 2, class 2M lasers are restricted to the visible range, 400 to 700nm. Protection of the eyes is provided by the aversion response. They may be hazardous if observed using viewing optics under two conditions:

a) if the beam is diverging and optics are used within 100mm of the laser aperture to collimate or concentrate the beam into the eye, or

b) if the beam is a large diameter and collimated and optics are used to increase the proportion of the beam that can enter the eye.

A label with hazard warning symbol and an explanatory label as below are required:-

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Class 3R  

Class 3R lasers can have any wavelength between 302.5 and 106nm. The AEL is within five times the AEL of class 2 in the visible (400 to 700nm) and within five times the AEL of class 1 at all other wavelengths. The ’R’ refers to ’Relaxed’ since this class is a relaxation of the 3B classification.

A label with hazard warning symbol is required for all wavelengths.

For wavelengths 400nm-1400nm ONLY the following explanatory label is needed:

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For other wavelengths the following explanatory label is needed:

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Class 3B  

Class 3B applies to both visible and invisible lasers. Direct intra-beam viewing near these devices is always hazardous. Viewing diffuse reflections is normally safe provided the eye is no closer than 13cm from the diffusing surface and the exposure duration is less than 10s.

A label with hazard warning symbol and an explanatory label as below are required:-


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Class 4

Class 4 lasers are hazardous for direct intra-beam, direct reflected and diffuse reflected beam viewing. They may cause eye or skin injuries and also may constitute a fire hazard.

A label with hazard warning symbol and an explanatory label as below are required:-

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class4


Aperture Labels for Class 3R, Class 3B & Class 4 lasers.


Each Class 3R, Class 3B and Class 4 laser product must display a label close to where the beam is emitted bearing the words 'LASER APERTURE' or 'AVOID EXPOSURE - LASER RADIATION IS EMITTED FROM THIS APERTURE'. This label can take the form of an arrow if this displays more meaning:-

aperture

Radiation Output and Standards Information.

All laser products, except for low power Class 1 devices, must describe the following details on an explanatory label :-

  • maximum output
  • emitted wavelength
  • whether laser beam is visible, invisible or both
  • pulse duration (if appropriate)
  • name and publication date of classification standard