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Labeling Requirements for Laser Windows and View Ports

R. James Rockwell, Jr.
Rockwell Laser Industries
The Background

The following question was recently raised by a corporate LSO:

"One of our sites is receiving a laser product that has built-in protective windows.  The Site LSO has requested that the windows of the product be labeled per the ANSI Z136.1 Standard’s paragraph 4.6.5.2".

For the record, that section states: 

4.6.5.2 Labeling of Laser Protective Windows. All laser protective windows shall be labeled with the optical density and wavelength(s) for which protection is afforded (see Section 4.6.2.4). All laser protective windows should also be labeled with the threshold limit (TL) and exposure time for which the limit applies and the conditions under which protection is afforded.

Note that the referenced section 4.6.2.4 is a list of 17 factors related to the choosing appropriate laser protective eyewear. Hence, referencing this section implies equivalence between laser protective eyewear and laser protective windows (view ports).

It is noted also that the LSO of the laser manufacturer had concluded that paragraph 4.6.5.2 applies only to protective windows in a facility and not a to the laser product, while at the same time citing the absence of such labeling requirements for built in windows (view ports) in the FDA/CDRH’s Federal Laser Product Performance Standard (FLPPS).

The Question

The Site LSO asked, "Which is the correct interpretation of the ANSI Z136.1 Standard.  Does it apply to only windows in the doors and walls, or equally to equipment view port windows?"

Review and Analysis

In the discussion, the Corporate LSO indicated that it appeared to him that paragraph 4.6.5.2 on Labeling of Laser Protective Windows is quite broad in its application and could be applied to each condition.

However, he also understood the claim of the manufacturer’s LSO and noted that an earlier paragraph in Section 4.6.3 addresses just "facility windows" exclusively; but what about 4.6.5.2?"  

Reviewing, ANSI Z136.1 Section 4.6.3 states:

4.6.3 Facility Window Protection (Class 3b or Class 4). Facility windows (exterior or interior) that are located within the NHZ of a Class 3b or Class 4 laser or laser system shall be provided with appropriate absorbing filter, scattering filter, blocking barrier, or screen which reduces any transmitted laser radiation to levels below the applicable MPE level.

Such laser windows shall be specifically selected to withstand direct and diffusely scattered beams. In this case, the window barrier shall exhibit a damage threshold for beam penetration for a specified exposure time commensurate with the total hazard evaluation for the facility and specific application (see Appendix C).

Important in the selection of the window are the factors of flammability and decomposition products of the window material. It is essential that the window not support combustion or release toxic airborne contaminants following a laser exposure.

This dual problem ("user – versus- manufacturer") is an often the recurrent problem with many laser equipment manufacturer’s who have shown a reluctance to interpret that the ANSI Z136.1 Standard may be applicable to them as a "requirement" in a manner similar to the FLPPS. Here are some review and comments:

FDA/CDRH FLPPS

First note that the FLPPS has a specific section: 21CFR1040.10 (f)(8) that states:

(8) Viewing optics. All viewing optics, view ports, and display screens incorporated into a laser product, regardless of its class, shall limit the levels of laser and collateral radiation accessible to the human eye by means of such viewing optics, view ports, or display screens during operation or maintenance to less than the accessible emission limits of Class I and table VI. For any shutter or variable attenuator incorporated into such viewing optics, view ports, or display screens, a means shall be provided:

(i) To prevent access by the human eye to laser and collateral radiation in excess of the accessible emission limits of Class I and table VI whenever the shutter is opened or the attenuator varied.

(ii) To preclude, upon failure of such means as required in paragraph (f)(8)(i) of this section, opening the shutter or varying the attenuator when access by the human eye is possible to laser or collateral radiation in excess of the accessible emission limits of Class I and table VI.

Thus, the FLPPS "approach" is that all "view ports" are, in a performance sense, equivalent to the protective housing and that no special labeling is required but that the view port ("window") must reduce the levels to Class 1 or below.

ANSI Z136.1 For the Safe Use of Lasers" Standard

First and foremost, the ANSI Z136.1 Standard is a User’s standard and is applied by USERS.

None-the-less, a Corporate LSO definitely has the "authority" to "require" a manufacturer to supply equipment that is "compliant" with the ANSI Z136.1 Standard on any specific aspect.

For example, some companies actually write such a "requirement" into their purchase orders (e.g. "All laser equipment supplied must meet all requirements as specified in the ANSI Z136.1 Standard and/or as requested by the Laser Safety Officer").

Note that portions of ANSI Z136.1, Section 1.3.2 state:

1.3.2.3 Control Measures. The LSO shall be responsible for assuring that the prescribed control measures are in effect, recommending or approving substitute or alternate control measures when the primary ones are not feasible or practical, and periodically auditing the functionality of those control measures in use (see Section 4).

This shall include, but not be limited to, such actions as establishing an NHZ, approving standard operating procedures (SOPs), avoiding unnecessary or duplicate controls, selecting alternate controls, conducting periodic facility and equipment audits, and training.

1.3.2.5 Protective Equipment. The LSO shall recommend or approve protective equipment i.e., eyewear, clothing, barriers, screens, etc., as may be required to assure personnel safety. The LSO shall assure that protective equipment is audited periodically to ensure proper working order.

1.3.2.6 Signs and Labels. The LSO shall approve the wording on area signs and equipment labels.

Also note that if the LSO makes (or affects) laser system modifications, then FLPPS certification questions/concerns are perhaps raised as indicated in Sections 4.1.2 and 4.3 below:

4.1.2 Laser System Modifications The LSO may reclassify, using the provisions and requirements of this standard, a given laser or laser system which has been modified. However, one should note that lasers and laser systems which have been altered by other than the user may necessitate recertification, reclassification, and compliance reporting under the requirements of the Federal Laser Product Performance Standard (FLPPS).

The question as to whether the ANSI Z136.1 specifications on windows are applicable to EQUIPMENT windows is specifically covered in the Engineering Controls sections:

4.3 Engineering Controls. The engineering controls for a laser or laser system are as specified in 4.3.1 to 4.3.14 and are summarized in Table 10.

Commercial laser products manufactured in compliance with the Federal Laser Product Performance Standard (FLPPS) will be certified by the manufacturer and will incorporate only those engineering controls required by the FLPPS. The LSO shall effect any additional engineering control measures that are required as outlined in this section.

The use of the additional controls outlined in this section shall be considered in order to reduce the potential for hazard associated with some applications of lasers and laser systems.

Engineering controls (performance features) which are supplied by the manufacturer of certified products and are used in this document are described in 4.3.1, 4.3.2, 4.3.3, 4.3.4, 4.3.5.1, 4.3.7, 4.3.8, 4.3.9, 4.3.9.1, and 4.3.14

The standard then specifically addresses viewing windows in equipment in ANSI Z136.1, Section 4.3.5:

4.3.5 Viewing Windows, Display Screens, and Collecting Optics. In order to adequately address additional protection requirements, it is sometimes necessary to utilize a number of various protective devices such as viewing windows, display screens, and laser barriers as defined in Section 2.

4.3.5.1 Viewing Windows and Diffuse Display Screens (All Classes). All viewing windows and diffuse (reflective or transmitted) display screens included as an integral part of a laser or laser system shall incorporate a suitable means (such as interlocks, filters, attenuators) to maintain the laser radiation at the viewing position at or below the applicable MPE as determined by the LSO for all conditions of operation and maintenance (see Section 4.6.2.5.2).

Important in the selection of window and display screen material are the factors of flammability and decomposition products of the material. It is essential that the material used for viewing windows and diffuse display screens does not support combustion or release laser-generated airborne contaminants (LGAC) above the current occupational limits following exposure to laser radiation unless the proper safeguards are in place to insure personnel safety (see Section 7).

In the following, one needs to define, I guess, what is meant by the term "window". Based on the discussions above and the sections below, I would conclude that a window could be located in a wall or door of EITHER the room or the laser enclosure (which in some cases is the room).

This leads to the ANSI Z136.1 Sections in question:

4.6.3 Facility Window Protection (Class 3b or Class 4). Facility windows (exterior or interior) that are located within the NHZ of a Class 3b or Class 4 laser or laser system shall be provided with appropriate absorbing filter, scattering filter, blocking barrier, or screen which reduces any transmitted laser radiation to levels below the applicable MPE level.

Such laser windows shall be specifically selected to withstand direct and diffusely scattered beams. In this case, the window barrier shall exhibit a damage threshold for beam penetration for a specified exposure time commensurate with the total hazard evaluation for the facility and specific application (see Appendix C).

Important in the selection of the window are the factors of flammability and decomposition products of the window material. It is essential that the window not support combustion or release toxic airborne contaminants following a laser exposure.

4.6.5 Labeling of Protective Equipment (Class 3b or Class 4). All protective equipment shall be permanently labeled as specified below:

4.6.5.2 Labeling of Laser Protective Windows. All laser protective windows shall be labeled with the optical density and wavelength(s) for which protection is afforded (see Section 4.6.2.4). All laser protective windows should also be labeled with the threshold limit (TL) and exposure time for which the limit applies and the conditions under which protection is afforded.

Summary and Conclusions

In conclusion, I do not view the requirements on "laser windows" much differently than the requirements on "laser protective eyewear." In both cases, the manufacturer of the protective device has the responsibility to provide the informative labels relating to the performance of the protective device as specified in the standard (e.g. wavelength, OD, Damage Threshold Levels …etc.).

In a similar fashion, in my opinion, the Laser System manufacture that may incorporate a laser window (e.g. view port) in the equipment has a similar responsibility to provide the SAME labeling as would the original window manufacturer. Not to do so would be equivalent to a laser manufacturer who supplied laser protective eyewear with the laser equipment in an unlabeled fashion stating that it was "not required" by FDA/CDRH FLPPS.

I always lean towards providing complete information, and then there is usually less uncertainty and ultimately more safety!