Laser Safety Sign Changes Cause Confusion

Ken Barat, lasersafetysolutions@gmail.com

In 1969 the U.S. Department of Labor, seeing the growth of laser applications in industry, the military, research and development labs, and universities, asked the American National Standards Institute (ANSI) to oversee the development of a standard ensuring their safe use. The standard aimed to provide guidance for individuals who work with high-power Class 3B and Class 4 lasers and laser systems, and to protect employers, facilities and personnel from beam hazards and nonbeam hazards such as exposure to hazardous gases, laser dyes and contaminants.

Sample ANSI Z535.2 Compliant Class 4 Laser Controlled Area Danger Sign Format, from ANSI Z136.1-2014 American National Standard for Safe Use of Lasers. The primary difference in the 2014 version is the requirement to put optical density and wavelength density on the sign. Previously this had not been a requirement. Courtesy of © 2014, Laser Institute of America. All rights reserved.

This is how the laser Z136 committee was formed, and in April 1973 the first “Safe Use of Lasers” standard was published. One result of the standard was the creation of warning signs and label requirements — the best known being the “Danger” sign that first appeared in an official capacity. While the Z136 series of laser standards is officially only guidance to laser users, it’s what the Occupational Safety and Health Administration (OSHA) and other regulatory groups rely on for laser safety protocols.

The hallmark red Danger sign has been the standard entryway posting for 43 years and is posted wherever Class 4 lasers are in use. The sign has gone through some minor changes over the years, but the prominent messaging has remained the same.

In 2014, however, a major change took place. The prominent “Danger” wording was replaced with the word “Warning,” and the background was altered from red to orange. But despite this fairly seismic change, all previous “Danger” versions were grandfathered in and are therefore compliant with the new standard. Many, if not most, remain in place.

Sowing seeds of confusion

And herein lies the confusion. The word “danger” implies a high risk of fatality if one is exposed to the hazard, whereas the word “warning” indicates a lesser risk. The rationale behind the change was to bring the prior Z136.1 standard and ANSI sign standard Z535.2 in harmony with one another; this prevents a facility from being cited by an inspector for not being compliant with the preferred standard. Today, the word “danger” is only required for laser systems of 1 kW and above.

Sample ANSI Z535.2 Compliant Warning Sign for Class 3B and Class 4 Laser Controlled Areas, from ANSI Z136.1-2014. One difference in the latest ANSI standard was that indication of laser type and output was now optional. Courtesy of © 2014, Laser Institute of America. All rights reserved.

In many ways, the decision demonstrates a shortcoming of the ANSI consensus standard process. ANSI’s official role is to ensure that each ANSI standard follows a set procedural approach. There is no technical review of content to ensure if one standard is compatible with an existing ANSI standard. The standards secretariat, which publishes the standard, is likewise concerned with following procedure — and does not play a role in reviewing technical content. That is left to the standard committee.

Every Z136.1 standard states, “Signs and labels prepared in accordance with previous revisions of this standard are considered to fulfill the requirements of this standard.” With such a blanket, get-out-of-jail statement, why should any facility wish to spend money and efforts to change laser warning signs?

Grandfathering in these signs, in this author’s mind, is a mistake. Today a 10-W laser could be in one room with a “Danger” sign on the door and there could be a 999-W laser in the room next door with a “Warning” sign posted, and both would be acceptable, per the standard. Either all signs should be changed or all should be left alone to maintain consistency in a workplace.

In a related issue in industrial settings, lasers in the hundreds of watts or kilowatt output range warrant the “Danger” descriptor. Many of these systems are designed or configured as Class 1 products, meaning that during intended operation or normal use they do not present a hazard to the operator or anyone in the area. Therefore, no control measures are required, but many still have a prominent red “Danger” sign that refers to the hazard classification of the laser itself, not the integrated system. A piece of equipment deemed completely safe to operate but with a glaring danger sign on the unit sends a mixed message and leads to unnecessary worker concerns and apprehension.

An evolution in laser safety signage over the years. The oval “Danger” sign (left) was used from 1973 through 1993, whereas by 2000 the signage incorporated an exclamation mark and the triangle. In 2014 the international safety symbol was added. From LIA’s Laser Safety Officer Training (course slides). Courtesy of © 2014, Laser Institute of America. All rights reserved.

Another major change to warning signs has been the wording on the sign beyond the signal word. The verbiage has become less prescriptive and the name of the laser and maximum output is no longer required. What’s more, the optical density and wavelength dominate — which is good. When looking at a warning sign, it is more useful to know what the optical density of the user’s protective eyewear should be and what wavelengths it must cover than the maximum output of the laser and its lasing medium.

For example, knowing a laser is a 150-W CO₂ laser isn’t enough information to determine eyewear requirements. Section 4.6.3.4 of the Z136.1-2014 standards outlining message panel information notes that laser type, pulse duration and maximum output “may be” included, but are not required. The previous standards, Z136.1-2007, required the type of laser or emitted wavelength, pulse duration and maximum output.

In summary, the area warning signs are used to define the boundary of the hazard zone and are still required, but the word describing the level of hazard has changed. The change relates more accurately to the level of risk. This change would most likely not have happened if committee members had known about or thought of checking the ANSI sign standards. Lasers can cause serious injury, but with engineering controls, a laser safety program, and by staying clear of the power supply, death or serious injury is unlikely.

Signal word definitions

Danger: Indicates an imminently hazardous situation that, if not avoided, will result in death or serious injury. The signal word is to be limited to the most extreme conditions. In Z136.1-2014, the Danger signal word indicates that death or serious injury will occur if necessary control measures are not implemented to mitigate the hazards within the laser-controlled area. This signal word is restricted to Class 4 lasers with high (e.g. multi-kilowatt) output power or pulse energies with exposed beams.

Warning: Indicates an imminently hazardous situation that, if not avoided, could result in death or serious injury. In Z136.1-2014, the Warning signal word “shall be used on the laser area warning signs associated with lasers and laser systems whose output exceeds the applicable maximum permissable exposure (MPE) irradiance, including all Class 3B and most Class 4 laser and laser systems.”

Caution: Indicates a hazardous situation that, if not avoided, could result in minor or moderate injury. In Z136.1-2014, the caution signal word “shall be used with all signs and labels associated with Class 2 and Class 2M lasers and laser systems that do not exceed the applicable MPE for irradiance.”

A look back at warning sign signal words through the years (Z136.1)

1973 — Signal words included only “Caution” and “Danger.” Caution signs were required for Class 2 and visible Class 3, from 1 to 5 mW. The signal word “Danger” is used with all signs and labels associated with Class 3 lasers other than those defined above and Class 4 high-power lasers.

1993 — The signal word “Danger” is used with all signs and labels associated with all Class 3b and Class 4 lasers and laser systems. “Danger” is in an Oval.

2000 — The signal word “Danger” is used on all Class 3B and Class 4 laser and laser systems. It is used for all signs and labels associated with all Class 3A laser and laser systems that exceed the appropriate MPE for irradiance. “Danger” is in a rectangle and includes an exclamation point.

2007 — “Danger” is used with all signs and labels associated with all laser and laser systems that exceed the applicable MPE for irradiance, including all Class 3R, Class 3B and Class 4 lasers and laser systems. The optical density of protective eyewear and wavelength is shown on the sign for a location requiring the use of eyewear.

2014 — Danger is restricted to those Class 4 lasers with high (e.g., multi-kilowatt) output power or pulse energies with exposed beams. The first appearance of the “Warning” signal word is in 2014.

The signal word “Warning” appears on laser warning signs associated with lasers and laser systems whose output exceeds the applicable MPE for irradiance, including all Class 3B and most Class 4 lasers and laser systems.