These early extinguishing devices consisted of a sealed glass sphere or bottle containing liquid chemicals, most commonly carbon tetrachloride. When smashed against a hard surface near the flames, the liquid vaporized into a dense gas that displaced oxygen and smothered the fire. Because carbon tetrachloride produces highly toxic phosgene gas when heated, these devices were eventually phased out and replaced by pressurized extinguishers.
Heard on the job
If you find an intact fire grenade in the walls during overhaul, leave it alone and get the hazmat team to secure it.
Insider tip
Collectors often find these in historic homes, but they pose a severe inhalation hazard if the fragile glass breaks and the chemical leaks.