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Laser Safety Standards Through the Years

Photonics Spectra
Jun 2010
Ken Barat, Lawrence Berkeley National Laboratory, and Jerome E. Dennis, IET TC76

Shortly after the demonstration of the first ruby laser by Theodore Maiman at Hughes Research Laboratories in Malibu, Calif., in 1960, many other laboratories assembled crude laser devices, and the laser’s unique hazard characteristics did not take long to become apparent.

For example, researchers at the US Naval Material laboratory at the Brooklyn Boat Yard in New York purchased a ruby rod and vacuum-coated its ends with an aluminum film. They inserted the rod into a xenon flashlamp surrounded by aluminum foil, and sure enough, a red spot appeared on the laboratory wall many feet away. But the light vaporized the coating, and the ruby rod had to be recoated after every shot.

Experts from major corporations and from the government agreed that control measures had to be established in anticipation of the laser’s proliferation. Control measures for laser products and for laser users would be needed, they agreed.

Researchers began to determine the levels of wavelength and duration of exposure that would not be expected to cause injury to a person. The levels became known as maximum permissible exposures (MPEs) and are expressed in units of irradiance or radiant exposure (time-integrated irradiance); i.e., power or energy per unit area. Although measurements of irradiance and radiant exposure are relatively straightforward, the researchers also had to determine the area over which the power or energy would be averaged. This is defined by the area of a circular measuring aperture called the “limiting aperture” in the American National Standards Institute (ANSI) standards.

Once the MPEs were established, they had to apply these values to exposures that could be expected from laser products to determine whether the products would be hazardous in use. Initially, up to 10,000 s was considered reasonable for occupational exposure, and an 80-mm diameter was used to simulate a full day of occupational exposure and viewing with a large-aperture optical instrument.

With these measurement specifications, it is possible to determine whether a product is likely to produce exposures that will exceed the MPE. The level of emission from a laser product that equals the MPE (under the specified conditions of measurement) is defined as the accessible emission limit (AEL) of Class 1. Tables of expressions for AELs were drawn up by bioeffects experts – mainly from the military – and from what is now the Center for Devices and Radiological Health (CDRH), as functions of wavelengths and emission durations similar to those for the MPEs. It also was recognized that there are gradations of hazards depending upon the extent to which the AEL of Class 1 or Class I was exceeded.

The experts agreed that the following classes of laser products were appropriate:

Class 1 or I: Not recognized to be hazardous.

Class 2 or II: Visible wavelengths; only hazardous for staring directly into the beam for longer than 0.25 s.

Class 3A or IIIa: Similar to Class 2 or II for unaided viewing, but allowed up to five times higher power in large-diameter beams.

Class 3B or IIIb: Hazardous for direct eye exposure and may be a skin hazard at the upper end of the class.

Class 4 or IV: Hazardous for direct eye or skin exposure and also may be hazardous by reflection from diffuse surfaces and a fire hazard.

This classification scheme was adopted by both the FDA and the ANSI Z136 community, enabling a cohesive set of requirements to be developed. The Radiation Control for Health and Safety Act of 1968 gave the Bureau of Radiological Health (BRH), part of the FDA, authority to issue mandatory safety standards for products that electrically generate any kind of radiation and to establish reporting and recordkeeping requirements for manufacturers of such products. The BRH later was merged into the CDRH.

The CDRH/FDA Standard (21 CFR 1040)

With laser manufacturer input, a proposed laser product safety standard was published in the Federal Register (1973). It included product hazard classifications, measurement conditions for classification, controls and indicators based on classification, and warning labels, and it required safety information in operating and service instructions. The proposal also included additional requirements for medical laser products and established class limits for construction laser products and for laser products intended for use in entertainment and display. The proposal was refined in 1974 in response to comments received from the public and then published as a final regulation to become effective on Aug. 2, 1976, as 21 CFR 1040.10 and 1040.11. A number of adjustments were made to the standard in 1978 and 1985 (see Table 1).



TABLE 1: CFR adjustments

A number of adjustments were made to the standard in 1978 and 1985 (see Table YY).

• Permitting a separation distance from the laser to the measuring instrument to more realistically take into account peoples’ minimum visual accommodation distance.

• Establishing a new Class IIa, with a shorter maximum emission duration for classification for products that emit visible laser radiation that is unlikely to be viewed for extended times.

• Permitting the use of a 7-mm aperture for the measurement of radiant power and energy for classification, unless the product is likely to be used in locales where the use of telescopes or binoculars would be expected.

• Establishing registration, product listing and recordkeeping requirements for uncertified laser products sold as components or repair parts.

• Giving the agency authority to approve alternate means of safety with respect to beam attenuators and labeling without having to resort to the more cumbersome variance procedures.

• Permitting Class IIIa as demonstration laser products.



In 1992, members of the CDRH laser staff met with representatives of the military, industry and academia to explore ways to harmonize the CDRH standard and the International Electrotechnical Commission (IEC) standard 60825-1. The main differences at the time were that the IEC standard had different tables of AELs and measurement specifications for hazard classification and also included a guide for the safe use of lasers.

It was agreed that both standards provided reasonably similar safety measures, but the differences contributed to unnecessary costs to industry in designing two standards and invited confusion likely to cause noncompliance with both standards. As an interim measure, the CDRH published a guidance document for industry, Laser Notice 50, stating that it would not object to conformance to requirements of IEC standards 60825-1 and 60601-2-22 in lieu of a list of requirements of the CDRH standard. The CDRH has issued numerous other statements of policy and interpretation, but Laser Notice 50 is probably the most significant because it allows the use of IEC labeling on US products in lieu of CDRH labeling, thus removing dual labeling requirements. These, as well as the standards and regulations, are available at no charge at www.fda.gov/radiation-emitting products.

Horizontal and vertical standards

The CDRH standard at 21 CFR 1040.10 and 1040.11 contains requirements in §1040.10 (a horizontal standard; meaning it reaches across all the vertical/applications-specific standards) that apply to all laser products, while in §1040.11 (vertical standards that contain additional or modified requirements), the requirements apply to specific-purpose laser products:

§1040.11(a) – Medical laser products.

§1040.11(b) – Surveying, leveling and alignment laser products.

§1040.11(c) – Demonstration (light show or display) laser products.

Similar structuring occurs in the international standards. IEC 60825-1 is the horizontal standard and applies to all laser products, while the following vertical standards apply additional or modified requirements for laser products for specific purposes:

IEC 60825-2 – Fiber optic communications systems.

IEC 60825-4 – Laser guards (for high-power industrial laser machines).

IEC 60825-12 – Free-space optical communications systems.

IEC 60601-2-22 – Medical laser products.

Also within IEC Technical Committee 76, which is responsible for the 60825 series, is the responsibility for maintaining the 11553 series of standards of the International Organization for Standards (ISO) for laser-based materials processing machines.

The International Electrotechnical Commission (IEC)

Experts from several countries met in 1974 to organize a new Technical Committee 76 in the IEC to develop a standard for the safe use of laser products. The first edition of this standard was numbered 825 and consisted of three parts:

Part 1 – Scope and definitions.

Part 2 – Equipment, labeling and informational requirements.

Part 3 – User’s guide.

Parts 1 and 2 were normative, or mandatory, in countries that adopted them as their national standard. These parts were very similar to the BRH/CDRH/FDA standard in requirements and in language. Part 3 was informative and contained tables of MPEs and general procedures for safe use. The IEC standards can be adopted by member countries of the IEC in whole or with exceptions. Because the CDRH/FDA standard is mandatory in the US, and because the CDRH/FDA has legal enforcement authority, the US has not adopted the IEC laser standard as its national standard.

When a standard is voted on by the IEC member countries, it is concurrently voted on by the CENELEC, the European Commission for Electrical and Electronic Standards. If approved, the member countries of CENELEC publish the standard as a CENELEC standard designated with the code EN. However, in the EC, the EN standards are not in themselves mandatory but are used as criteria of conformance with the mandatory European Directives.

The first edition of IEC 60825 was published in 1984. Revisions have been made to the current edition, IEC 60825-1, Edition 2, which was published in 2007.

Although these revisions have been occurring in response to advances in photobiological science and experience, the CDRH standard has remained static because of a lack of resources needed to keep up. In the early 1990s, the scope of 60825-1 was expanded to include LEDs because of their electrical and mechanical similarities to laser diodes. However, the latest edition has dropped LEDs because they do not have the radiance of lasers. IEC adopted the standard of the International Commission on Lighting (CIE) as a joint IEC/CIE standard for the Photobiological Safety of Lamps and Lamp Systems in which the hazards of LEDs are now being addressed.

IEC TC 76 has published the following additional standards, each first published in the years shown:

60601-2-22 Class 3B and 4 medical laser systems – 1992.

60825-2 Fiber optic communications systems – 1993.

60825-4 Guards for industrial laser machines – 1997.

60825-12 Free-space optical communications systems – 2004.

62471 Photobiological safety of lamps and lamp systems – 2006.

IEC TC 76 is responsible for the maintenance of the ISO 11553 series standards for laser-based machine tools and has published a number of guides and technical reports dealing with applications, measurements and testing. The IEC standards are available from the US National Committee for the IEC at www.ansi.org , the IEC at www.iec.ch or the Laser Institute of America at www.laserinstitute.org.

Laser radiation safety limits based on the horizontal standard 60825-1 are incorporated into standards of other technical committees, including for electrical toys, home entertainment products and personal computers.

US laser users standards

The first American National Standards Institute standard for the “Safe Use of Lasers Z136.1” was published in 1973 at the request of the CDRH. As applications of lasers matured, many applications-based laser standards were developed. The goal of these standards is to provide a safety backbone for users and user facilities onto which safety programs can be built.

Z136.1 is a horizontal standard. With each revision of it, biological effect (MPE) information has been refined and page count has grown. Unfortunately, clarity has not been a central concern, which of course allows consultants to make a living. There is now an attempt with the new standards and revisions of existing ANSI Z136 standards to trim Z136.1 and make all the standards user-friendly. One of the first tangible signs of this user-friendliness has been the incorporation of an index in the Z136.1-2000 version. As laser applications have advanced, a number of application standards have come into being (see Table 2).
 


TABLE 2: Application standards

ANSI Z136.1-2007 for Safe Use of Lasers – first edition, 1973.

Z136.2-1997 for Safe Use of Optical Fiber Communication Systems Utilizing Laser Diode and LED Sources – first edition, 1977.

ANSI Z136.3-2005 for Safe Use of Lasers in Health Care Facilities – first edition, 1988.

ANSI Z136.4-2005 RP for Laser Safety Measurements, Hazard Evaluation and Instrumentation.

ANSI Z136.5-2009 for Safe Use of Lasers in Educational Institutions – first edition, 2000.

ANSI Z136.6-2005 for Safe Use of Lasers Outdoors – first edition, 2000.

ANSI Z136.7-2008 for Certification & Testing of Laser Eyewear and Barriers.

In draft:

ANSI Z136.8 – Safe Use of Lasers in Research, Development & Training (maybe late 2010).

ANSI Z136.9 – Safe Use of Lasers in Manufacturing Environments.

ANSI Z136.10 – Safe Use of Lasers in Entertainment, Displays and Exhibitions.



Although every state has a program regulating ionizing radiation, only a few have a laser regulatory program. The major programs are in Arizona, Texas, New York, Massachusetts and Illinois. The reason for this is reluctance by state government to take on the perceived cost of a laser safety program. This has not stopped 30 states from addressing who can do cosmetic laser surgery (i.e., hair removal) or local municipalities from passing laser pointer rules. The most recent example is the Texas Legislature, which passed legislation that establishes a regulatory program for laser hair removal.

A number of groups also have made forays into laser safety:

• Federal Aviation Administration, FAA 7400.21 – Outdoor, laser use in air-space.

• National Fire Protection Association, NFPA 70E – The National Electric Code has a brief and confusing section on laser labs 330.

• ANSI B11 – Laser Marking Machines.

• NFPA 115 – Fire Code for Laser Safety, very much a firefighter-oriented document.

• Code of Federal Regulation – Export rules for laser technology are part of this code, which restricts both technology hardware and intellectual contacts.

In conclusion, consider that today you can buy a 1500-mW handheld laser. The goal of standards and regulations is to ensure safety for users and products as well as consistent approaches to safety evaluation. The review process for ANSI and IEC standards allows these documents the opportunity to stay current with – or at least only a few years behind – laser technology, which will continue to advance in areas we can only imagine today.

Meet the authors

Ken Barat is the laser safety officer for Lawrence Berkeley National Laboratory and the author of Laser Safety: Tools & Training and Laser Safety Management. He is a member of several ANSI committees; e-mail: kbarat@lbl.gov.

Jerome E. “Jerry” Dennis is in his third term as chairman of IEC TC 76. He retired from the CDRH/FDA in 2008 and has since been active as a consultant in laser product safety. He is past vice chairman of ANSI Z136 and has remained active in Z136 and in its subcommittees. He previously spent 15 years in industry in research and development of laser systems for military, industrial and laboratory applications. He was a member of the US Department of Defense laboratory team in Brooklyn, N.Y., that purchased and coated the ruby rod mentioned above; e-mail: jerodeni2@comcast.net.

Acknowledgments

The authors wish to thank David Sliney, Robert James, Jim Smith and Remy Baillif for contributing information used in this paper.


GLOSSARY
ruby laser
The optically pumped, solid-state laser that uses sapphire as the host lattice and chromium as the active ion. The emission takes place in the red portion of the spectrum.
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