Safer emergency flares, thanks to a less toxic and more stable chemical for making smoke

Many emergency flares rely on a material called red phosphorus, one of the natural forms of the element, to produce billowing smoke that draws the rescuers’ attention. Researchers have been seeking an alternative because red phosphorus has multiple safety flaws. For example, it can ignite with a bit of impact or friction; red phosphorus is often added to match heads to help them ignite. Although useful in a match, the compound’s propensity to explode when handled in bulk amounts is a danger to factory workers and during transportation. Furthermore, when the chemical is exposed to moist air—common in marine emergency situations—it can degrade into toxic phosphine, PH₃, which causes a range of symptoms in people, including vomiting, breathing difficulty, and pulmonary edema. A team led by Stanisław Cudziło of the Military University of Technology in Warsaw and Ernst-Christian Koch of Lutradyn, an energetic materials company, have come up with a safer alternative: phosphorus(V) nitride, P₃N₅ (Angew. Chem. Int. Ed. 2016, DOI: 10.1002/anie.201609532). Unlike red phosphorus, P₃N₅ won’t ignite with friction or sudden impact, nor will it degrade in moist air to harmful compounds.