Late in 2007 saw the publication of BS EN 60825-1:2007.  This revised prime standard for laser products immediately follows adoption of the EN standard which itself accurately reflects the revised IEC standard IEC 60825-1:2007.  These standards supersede the earlier version of 60825-1:1994 together with subsequent amendments and any corrigenda.

It should be noted that for compliance purposes within the EU, either version of the standard may be used up to September 2010 as that is the date at which the earlier version of the EN standard must be withdrawn.  However where the IEC standard is used for compliance purposes (presumably at least all compliance claims on equipment going outside the EU) then IEC60825-1:2007 must be used as IEC withdrew all earlier editions of the standard immediately on publication of the 2007 document.  This latter situation will also mean a revision of other IEC documents where individual requirements and clause numbers references have changed as a result of this new edition.  For example, IEC 60825-4 for laser guards will be reissued with revised references when the next Annex is published (later in 2008).

Standard 60825-1:2007 has changed for two major reasons.  Light emitting diodes (LEDs) have been removed from the standard as has the User’s guide notes. However there are also a number of other changes, some of which are important.

In this context LEDs that have been removed from the scope of the safety standard, are those that are derived from semiconductor devices having large sources sizes producing optical radiation that may not be coherent.  It has been widely felt that these devices were generally not hazardous and that classification requirements were inappropriate.  Generally LEDs need now to be considered using the IEC standard IEC 62471:2006 (CIE S009:2002) Photobiological safety of lamps and lamp systems.  There is still considerable concern relating to high power LEDs especially those producing ultra-violet light as longer term exposure may be hazardous due to the cumulative effects of UV exposure.  Semiconductor devices that may generally be known as LEDs but produce spontaneous or stimulated coherent radiation are still covered by the 60825-1 standard.

Of course, removal of the User’s Guide, previously included in Section 3 of the older 60825-1 standard, should not be a surprise following the publication a couple of years back in 2004 of standard IEC TR 60825-14 – User’s Guide.  However not all user information has been removed from the revised Part 1.  Annex A now collects together most of the information relating to Maximum Permissible Exposure (MPE) values.  Annex B still gives examples of calculations. Annex D describes the biophysical consideration with Annex E giving additional information to aid the expression of MPEs and Accessible Emission Limits (AELs) as radiance.

The classification system as described in the standard has not changed although there are minor additional requirements.  For example, in the case of highly divergent laser sources, measurements for classification purposes made using the measurement aperture diameters and measurement distances for the default evaluation as shown in Table 11 may show that laser output is below the AEL for Class 1.  But due to the highly divergent characteristic of the beam, exposure at a distance closer to the source than the measurement distance may cause injury.  In this case additional labelling is now required to warn the user of this hazard.

Some of the definitions have been expanded.  The definition for “accessible emission” has been added to clarify whenever the term ‘emission level’ is used and how this term should be considered with beam diameters that are larger than the classification measurement aperture.

The definition for “human access” has now four conditions: being:-

1. ability of the human body to meet laser radiation emitted by the laser product, i.e. radiation that can be intercepted outside of the protective housing, or
2. ability of a cylindrical probe with a diameter of 100 mm and a length of up to 100 mm to intercept levels of radiation of Class 3B and below, or
3. ability of a human hand or arm to intercept levels of radiation above the AEL of Class 3B,
4. also, for levels of radiation within the housing that are equivalent to Class 3B or Class 4, ability of any part of the human body to meet hazardous laser radiation that can be reflected directly by any single introduced flat surface from the interior of the product through any opening in its protective housing.

The standard is not now divided into Sections.  Clause 4 still lists the engineering requirements.  Within this Clause, subclause 4.5 includes an additional requirement for Class 4 laser systems of a Manual Reset.  This control shall be incorporated to enable resumption of operation following interruption of emission caused by the use of the remote interlock or interruption of the power source.  Subclause 4.12 relating to “Walk-in” protective housings adds the requirement that where “walk-in” access during operation is intended or reasonably foreseeable, engineering means shall be used to prevent exposure of those persons inside the enclosure above the equivalent of Class 3R.  Clause 5 specifies the labelling requirements for laser products.  Clause 6 gives the requirements for information including that information for the user and that intended for servicing and for purchasing.  Clause 8 describes the classification rules and includes direction on the responsibility for classification.  Clause 9 specifies how AELs are determined when tests and measurements are made for the purposes of classification.  It should be noted that the Table indicating AELs for various Classes of laser are shown in Table 4 to 9 inclusive.  Two tables for each of Class 1 (and 1M) and Class 3R are given – one where the constant C6 equals 1 and the other table for extended sources where C6 may have some other value.  The interpretations when considering measurement geometries are expanded by the inclusion of Figure 5 for extended sources (note: many feel that is still not clear and further work is going on to improve understanding).

As the User’s guide has been removed, the requirements within the standard end with Clause 9.  However for information purposes only, MPE values are still included within the standard and are described in Annex A together with the relevant tables (giving MPE limits for various wavelengths and exposure durations).  Note again that two tables are given with Table A.1 being for MPE limits when the constant C6 is equal to 1 and Table A.2 being for extended sources when C6 may equal some other value.  Table A.3 gives the exposure limits for skin.  There have been no changes to the MPE limits which are a reflection of the levels specified by the International Commission on Non-Ionising Radiation Protection (ICNIRP).

Will this standard change again? – probably not greatly.  It is understood that there are a few typos, which will need a correction.  There is still concern about the treatment of extended sources (including discussion about Figure 5) and, of course, there is the continual discussion to produce a labelling system that does not require the use of language (a discussion that has been going on for over ten years and seems no nearer to a satisfactory resolution).  There are also rumours that MPE levels may be amended by ICNIRP but nothing firm.  The current MPE levels are felt to be very conservative and have proved themselves by years of practical application.  Test houses are still concerned that the sequence of specification used for the requirements in this standard do not lend itself readily to the obvious sequence of testing and may influence any further editions of this standard.  Try looking at the checklist specification in IEC TR 60825-5 and the concern in understandable.

In conclusion, this standard is a worthwhile edition of only for the removal of LEDs from the scope and the final transfer of the user guide away to Part 14.