Safety Week: Study Sets Sights on SCBA Lens

A study has found that the weakest link in a firefighter's PPE is the facepiece lens.

Part of the recommendations will be for new testing that includes radiant heat panels that will more realistically mimic heat flux and temperatures experienced in fires.

Bryner is also proposing that additional testing be created to simulate firefighters wiping the facepiece with a gloved hand. As the polycarbonate material degrades, it becomes milky in color and firefighters may try to wipe lenses, which could cause substantial damage when the material is softened.

Interestingly, the testing showed that a facepiece could develop a hole of up to a half-inch in size and still maintain life, provided there was a positive flow of air in the mask. In fact, the flow of air cools the facepiece lens and could make it last longer, Bryner said.

There are other kinds of materials that could work for lenses, he said. Polyethersulfone has a deflection temperature of 401 degrees compared to 284 degrees for polycarbonate, and has a melting temperature of between 644 degrees and 734 degrees, compared to 437 degrees and 599 degrees for polycarbonate.

"Polyethersulfone has significantly better performance, but it does have a little bit of color to it," Bryner said. "There is a trade off that the committee will have to review."

There are some other products that might work as well, but they have to be flat to work at their peak and that would require significant redesign of the facepiece, and may prove unacceptable to firefighters who have become accustomed to wide views and peripheral vision.

He said material that resembles bulletproof glass may also provide a solution to more heat-resistant lenses, but the price may be prohibitive. Initial inquiries suggest the price would be $1,400 for an SBCA facepiece lens.

It is not, however, the mission of NIST to consider price when doing research, he said, noting that the organization is devoted to the science and testing of materials. The political aspects and tradeoffs come in when the rules and standards are made.

Other options include metal coatings of the lens, Bryner said, noting that firefighters in Europe and South America are used to gold-coated lenses. That however, comes at an optical price with a 50 percent reduction in transparency.

"We think there are some good tradeoffs to be made to keep firefighters safe," he said.