Posts Tagged National Institute of Standards and Technology (NIST)

Fire Service News


In the real world, fuel fires must be quenched with special kinds of chemicals, and the ones that have been most commonly used are known as aqueous film-forming foams (AFFFs). However, environmental and health concerns about AFFFs have launched widespread efforts to detect, monitor and eventually eliminate them. Now, researchers at the National Institute of Standards and Technology (NIST) have released new reference materials to expedite these efforts.

What makes the foams so effective are chemical compounds called per- and polyfluoroalkyl substances (PFAS), enabling them to suppress fuel fires much more quickly and efficiently compared with other alternatives. Unlike water dumped on a flame, which wouldn’t work in a scenario where a flammable liquid is causing the fire, the foams not only spread over the fire but prevent it from reigniting by suppressing oxygen flow and fuel vapors. AFFFs were first introduced in the 1940s and have been used since that time not only in emergencies but also in firefighter training exercises. 

Due to their significant ability to resist heat and chemical changes, the PFAS in these foams break down slowly over time, giving them the name “forever chemicals.” The foams can easily leak into nearby water and soil and affect the surrounding ecology, raising concerns because PFAS have been linked to negative health effects such as certain cancers. 

Because of these concerns, organizations including the Department of Defense (DOD)  are starting to eliminate the use of PFAS-containing materials. Under the 2020 National Defense Authorization Act, the DOD will be required to stop purchasing AFFFs from manufacturers by October 2023 and will stop using them by October 2024. 

To help with this phaseout, NIST researchers have collaborated with the DOD on a series of AFFF reference materials (RMs) containing PFAS. During the phaseout process, older AFFFs will still be around, and the RMs will help organizations identify foams with PFAS so they can remove them from use. 

While manufacturers aim to meet the new military specifications for their foams to contain less than 1 parts per million (ppm) PFAS, “There are still legacy AFFFs sitting across the country, and they will need to have measurements made to show if they contain PFAS,” said NIST chemist Jessica Reiner. “If they do contain PFAS, then they will need to be disposed of properly.” 

NIST has released four RMs containing different formulations of PFAS in the foams. 

“These four RMs contain many of the different PFAS used in the legacy AFFFs that are being phased out. The RMs are useful for labs that want to test for these,” said Reiner.

The RMs will also help the military when purchasing alternative fire suppressants.

“Because the military has to stop purchasing these foams, they need to test for PFAS in the new foams that they buy. By having these RMs, they can measure for PFAS. Manufacturers producing new foams could also use the RM when they need to test if they are PFAS free,” said Reiner. 

NIST researchers sent the RMs to a number of other labs to be tested in what’s called an interlaboratory study. They learned scientists had a hard time measuring PFAS in foam form. NIST researchers then designed the new reference materials in a specific way so that each individual formulation is diluted to make it easier to use. 

Analytical labs, academic institutions, and the U.S. Department of Transportation are a few other examples of groups that can use the RMs. “For example, anyone in a toxicology group could use these RMs for scientific experiments, such as delivering doses of the compounds to study their effects on cells,” said Reiner. 

RM 8690 PFAS in AFFF IRM 8691 PFAS in AFFF IIRM 8692 PFAS in AFFF III, and RM 8693 PFAS in AFFF IV are available from NIST. Organizations wishing to purchase the reference materials can visit the NIST Store

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Fire Service news

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A lack of oxygen can reduce even the most furious flame to smoldering ash. But when fresh air rushes in, say after a firefighter opens a window or door to a room, the blaze may be suddenly and violently resurrected. This explosive phenomenon, called backdraft, can be lethal and has been challenging for firefighters to anticipate.

Researchers at the National Institute of Standards and Technology (NIST) have a plan for informing firefighters of what dangers lie behind closed doors. The team obtained data from hundreds of backdrafts in the lab to use as a basis for a model that can predict them. The results of the study suggest that the model offers a viable solution to make predictions based on particular measurements. 

Currently, firefighters look for visual indicators of a potential backdraft, including soot-stained windows, smoke puffing through small openings and the absence of flames. If the cues are present, they may vent the room by creating holes in its ceiling to reduce their risk. If not, they may charge right in. Ultimately, they must rely on their eyes in a hazy environment to guess the correct action, and guessing wrong could come at a steep cost.

At NIST’s National Fire Research Laboratory, engineers conducted experiments where they lit a stream of gaseous fuel that poured into a small chamber and then sealed its door shut. In each case, the door remained closed for several minutes as they continued to pump gas into the chamber and the fire burnt itself out by depleting its available oxygen. Then, they remotely sprang open the door. Some experiments were rather uneventful, with no hint of reignition. In others, fireballs accompanied by pressure waves erupted in the doorway.

Throughout nearly 500 experiments, in which they altered factors such as the type and amount of gas injected into the chamber, they recorded temperatures, pressures, the dimensions of the fireballs and more. To determine the abundance of the fuel in particular, they improved upon an instrument developed at NIST decades prior called a phi meter.

The meter sampled fuel and air gas mixtures from the chamber, added a known amount of oxygen and then combusted the sample internally, measuring the difference in oxygen before and after. The less oxygen consumed in the reaction, the greater the relative abundance of fuel in the mixture.

They used a machine learning algorithm to establish a predictive backdraft model from their treasure trove of information. As an initial trial for the model, they fed it readings of gas concentrations, fuel richness and temperature taken at a single location in the chamber before the door opened during their experiments. Based on that information alone, the model had to estimate the chance of a backdraft occurring.

Taking an estimate of above 50% as an affirmative prediction and below 50% as a negative, the model was correct in 70.8% of the experiments it was tested on. The accuracy increased to 82.4% with the addition of measurements taken at a second location in the chamber.

The next steps are to develop a portable device that houses the measurement technology they used in the lab as well as their computer model and then battle-test the technology in a more realistic building fire scenario. They envision firefighters using a handheld device would either probe the air of a room through existing openings, such as cracks around a door, or create small openings.

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