In response to the increasing threat of flame events in conflicts over the last few decades there is increased demand for flame resistant (FR) uniforms to be fielded more quickly. While the FR uniforms have increased Soldier protection during a flame event, there is a question of the threat posed by the toxicity of the compounds evolved from those uniforms during and after a flame event. Of particular concern are the compounds released as a consequence of the flame event that the Soldier inhales.
The aim of this project was to identify the compounds that are evolved from currently-fielded FR uniforms upon heating. To accomplish this, the project team used a combination of pyrolysis-gas chromatography/mass spectrometry and thermogravimetric analysis. Once the evolved compounds were identified, each compound was assigned a hazard score based on a modified version of the Globally Harmonized System for acute toxicity inhalation. Those scores were weighted based on the relative amount of each compound detected. All the weighted scores for a material were summed to give a cumulative Material Rating Score. Multiple iterations of the Material Rating Score are discussed and further improvements for each are provided.
From the work described here it was possible to determine a large portion of the compounds evolved from pyrolysis of currently-fielded FR uniforms. By identifying the compounds evolved two different ratings systems were developed using different pyrolysis profiles. It was possible to rate the fabrics on their relative toxicity. In both versions of the rating system Fabric B had the highest Material Rating Score, indicating the highest toxicity. In both rating systems Fabric C had the lowest Material Rating Score indicating the lowest toxicity. Fabric C was also the only fabric studied that had no chlorine present.
The project team envisioned that these Material Rating Scores will serve as one metric, to serve alongside FR performance, when purchasing and fielding equipment in order to provide FR protection while minimizing negative health effects. While the focus of this work is on FR uniforms, the methodology is translatable to other areas of concern including burn pits and the incineration of per- and polyfluoroalkyl substance-containing sorbent material. Further work is needed to refine this methodology to conduct the pyrolysis and thermogravimetric analysis in real-world atmospheres containing oxygen. Also, incorporation of another technique, such as thermogravimetric analysis coupled with infrared, may lead to the identification of small molecules not captured here.