Why would you throw a fire extinguisher?

To grasp the practicality of throwable fire extinguishers, it helps to consider what goes into fighting a fire.

At its most basic, fire is just a fast, hot form of oxidation, the same basic chemical reaction that rusts old bumpers and turns cut fruit brown. It entails four elements -- fuel, heat, oxygen and an uninhibited chemical reaction -- that together form what firefighters call the fire tetrahedron: Heat something to its ignition temperature in an oxygen environment, and you get fire, which throws off more heat as it burns, which then sets new and interesting stuff ablaze or feeds back into the system and keeps the reaction rolling [source: NFPA].

At its core, firefighting means playing Yoko Ono to this Fab Four of Fire, but just what that means varies from fire to fire and can require great expertise to figure out. One key element in that calculation, so basic that it defines how the United States and other countries classify fires, involves the fuel's composition [sources: NFPA; OSHA]:

In truth, fighting any but the most basic fires takes years of training and experience in how fire spreads, affects structures, builds pressure in tanks, or changes moods in an instant. For instance, water, which cools fire and creates steam to crowd out oxygen, works well on Class A fires but makes grease fires and Class Cs more hazardous. Fighting Class B fires typically means establishing a smothering foam barrier, while Class D materials, which can churn out their own oxygen and hydrogen while burning, require sand or salt-based powders to smother (a salt is a compound formed from an acid-base reaction in which the acid's hydrogen is replaced by a metal or other positive ion) [sources: Encyclopaedia Britannica; NFPA].

Throwable fire extinguisher and balls don't avoid this problem; you still need to know the limited subset of fires covered by a given product. But, as we'll see in the next section, they do overcome other limitations of canister extinguishers, including bulk, upkeep and complexity of use.

We began tossing around throwable fire extinguishers, then called fire grenades, in the late 19th century, chiefly during the period from 1870-1910. Most consisted of glass bulbs that homeowners could chuck into a fire or mount in metal brackets (a fire's heat would melt the rack's solder, causing the grenade to smash on the floor). Fire grenades usually contained carbon tetrachloride, which dilutes flammable liquid fuels and forms a heavy gas blanket to helps block out oxygen. However, because carbon tetrachloride is poisonous and can produce the toxic chemical compound phosgene during a fire, such devices fell out of favor as fire extinguishers improved [sources: Burke; The Gas Age; Kovel and Kovel].

But some ideas die hard. Today, a Thailand company produces the Elide Fire Extinguishing Ball, a 5.8-inch (14.7-centimeter), 3.3-pound (1.5-kilogram) sphere that customers throw or roll into fire. After 3-10 seconds of exposure to flame, the ball explodes loudly (120 decibels) and scatters extinguishing agents, including FUREX 770, a dry chemical containing mono ammonium phosphate. The ball can put out small Class A and some small Class B fires over an 86-108 square-foot (8-10 square-meter) indoor area, and its loud bang can serve as an alarm [sources: Caldic Deutschland; Elide; YG Yangın Güvenliği].

Malaysia's Linnovate Technology offers the SOTERIA Throwable Fire Extinguisher, a 1.3-pound (600-gram) plastic resin bottle that withstands everyday pressures but shatters when dropped from 3 feet (1 meter), releasing organic and inorganic salts. These react with fire to generate carbon dioxide and ammonia gas, which disperse and extinguish the fire, as well as foam, which suffocates the fuel. It retails for $69.99 (at the time of publication) and douses Class A and B fires [sources: Lim; Linnovate].

Bonex, a Malaysian company headquartered in Japan, divides its throwable products according to fire fuel type. Its $85 SAT119 (named for the Japanese fire rescue number) resembles SOTERIA in form but handles only Class A fires. According to one store, it contains 16.9 fluid ounces (500 milliliters) of ammonium phosphate dibasic (a soluble ammonium phosphate salt used as an environmentally friendly flame retardant), and ammonium bicarbonate (a white powder found in baking powders and fire extinguishers). When exposed to fire, it emits carbon dioxide and ammonia gas. Bonex also makes FR911 FLAMEOUT for handling Class A, B and C fires [sources: Bonex; Japan Trend Shop; NJDHSS; Santa Cruz Biotechnology].

All three products contain nontoxic, eco-friendly chemicals and boast a five-year shelf life, according to manufacturers [sources: Bonex; Elide]. Regarding their legality in the Unites States, Linnovate CEO Leon Lim said, "SOTERIA Throwable has been exported to many countries and has always been classified as a non-dangerous good."