European & Australian / NZ Laser Safety Standards
An Overview of Laser Classification System in EN 60825-1, IEC 60825-1 and AS/NZS 2211.1:2004
In
2001 the standard governing the safety of laser products in Europe (EN)
and Internationally (IEC), was substantially revised and the
Classification system was overhauled. This resulted in the introduction
of three new laser classes (1M, 2M and 3R) and the abolition of Class
3A. Below is a brief description of each of the current laser classes.
The 60825-1 standards apply equally to lasers and LEDs. In most places
we have used the word "laser", but it can be replaced by "LED".
Generally speaking LEDs would be in the lower Classes (1, 1M, 2, 2M,
3R), but very exceptionally may be Class 3B. At the time of writing we
are not aware of any Class 4 LEDs*.
The phrase "eye-safe" is used below. Please note that "eye-safe" is
applicable to the whole optical spectrum from 180nm to 1mm wavelength,
not just in the retinal hazard range of 400nm to 1400nm. Outside the
retinal hazard range there is potentially a hazard to the cornea. A
wavelength outside the retinal hazard range is therefore not
automatically eye-safe!
Class 1
Lasers
that are safe under reasonably foreseeable conditions of operation,
including the use of optical instruments for intrabeam viewing. Laser glasses are not required for this Class.
Class 1M
Lasers
emitting in the wavelength range from 302.5nm to 4,000nm which are safe
under reasonably foreseable 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 100mm 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.
Classes 1M and 2M broadly replace the old class 3A under IEC and EN
classification. Prior to the 2001 amendment there were also lasers
which were Class 3B but were eye-safe when viewed without optical
instruments. These lasers are Class 1M or 2M under the current
Classification system.
In general laser glasses are not required to be worn for Class 1M lasers although in some circumstances it may be recommended.
Class 2:
Lasers
that emit visible radiation in the wavelength range from 400nm to 700nm
where eye protection is normally afforded by the 0.25s blink
reflex. This reaction may be expected to provide adequate
protection under reasonably foreseable conditions of operation
including the use of optical instruments for intrabeam viewing. (NOTE:
Outside the wavelength range from 400nm to 700nm, any additional
emissions of Class 2 lasers are required to be below the AEL of Class
1).
Laser glasses are not required to be worn with Class 2 lasers.
Class 2M:
Lasers
that emit visible radiation in the wavelength range from 400nm to 700nm
where eye protection is normally afforded by aversion responses
including the 0.25s 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 100mm 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.
(NOTE: Outside the wavelength range from 400nm to 700nm, any additional
emissions of Class 2 lasers are required to be below the AEL of Class
1).
In general laser safety glasses are not required to be worn for Class 2M lasers although in some circumstances it may be recommended.
Classes 1M and 2M broadly replace the old class 3A under IEC and EN
classification. Prior to the 2001 amendment there were also lasers
which were Class 3B but were eye-safe when viewed without optical
instruments. These lasers are Class 1M or 2M under the current
Classification system.
Class 3R:
Lasers
that emit in the wavelength range from 302.5nm to 10mm 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 from 400nm to 700nm and within five times the AEL of
Class 1 for other wavelengths.
Radiation in
this class is considered low risk, but potentially hazardous. The class
limit for 3R is 5x the applicable class limit for Class 1 (for
invisible radiation) or class 2 (for visible radiation). Hence CW
visible lasers emitting between 1 and 5 mW are normally Class 3R.
Visible class 3R is similar to class IIIA in the US regulations.
It is recommended that laser safety glasses should be worn for Class 3R lasers.
Class 3B:
Lasers that are normally hazardous when direct intrabeam exposure occurs (i.e. within NOHD).
Radiation in this class is very likely to be dangerous. For a
continuous wave laser the maximum output into the eye must not exceed
500mW. The radiation can be a hazard to the eye or skin. However,
viewing of the diffuse reflection is safe.
laser safety glasses are required to be worn for Class 3B lasers.
Class 4:
Lasers
that are also capible of producing hazaedous diffuse reflections.
They may cause skin injuries and could also constitute a fire
hazard. Their use requires extreme caution.
laser safety glasses are required to be worn for Class 4 lasers.
Any laser product of a given Class may contain 'embedded' lasers which
are greater than the Class assigned to the product, but in these cases
engineering controls (protective housings and interlocks) ensure that
human access to radiation in excess of product Class is not possible.
Notable examples of this are CD and DVD players which are Class 1 laser
products while containing Class 3R or Class 3B lasers and laser
printers which are Class 1 laser products but contain Class 4 embedded
lasers.
Note:- for a product to be classified correctly, it must be tested at
the maximum output accessible under reasonably foreseeable single-fault
conditions (eg in the drive circuitry). A non-M class product must pass
both Condition 1 and Condition 2 of Table 10 in IEC/EN 60825-1, and an
M-class product (which by definition has failed either Condition 1 or
2) must pass the irradiance condition in the same table.
* Generally speaking lasers are point sources while LEDs are extended
sources. Extended sources have higher power limits than point sources
for a given laser Class. Therefore a visible LED emitting 10 mW may be
Class 2, while a visible laser pointer of the same power would be Class
3B. NB Laser pointers above Class 2 are banned for sale to the public
by trading standards. |
