Why would you throw a fire extinguisher?

That student protester is actually throwing a regular fire extinguisher. That's not quite the same thing as one that's designed to be lobbed at a fire.
That student protester is actually throwing a regular fire extinguisher. That's not quite the same thing as one that's designed to be lobbed at a fire.
© Stringer/Chile/Reuters/Corbis

Judging from some ads on late-night TV, you would think that the average human being is incapable of peeling fruit, making salad or vacuuming a floor without hilarious calamity ensuing. Which might make you wonder: How can we possibly be trusted with putting out a fire?

In the midst of an emergency is a lousy time to realize that fire extinguishers are more than a point-and-shoot proposition. You need to properly store, charge and maintain them, understand how to activate and use them, and choose the right one for a given fire. It's a lot to think about in the, ahem, heat of the moment, which is why it's surprising that laws mandating that workplaces and homes stock extinguishers do not always require training in their proper maintenance and use.

It's a complex problem, and one that firefighters have grappled with since Ctesibius of Alexandria devised the first basic hand pump for directing water at a fire around 200 B.C.E. [source: Encyclopaedia Britannica]. Over time, it became clear that we needed more portable extinguishers and a wider array of snuffing substances to tackle different fuels and conditions: Water wouldn't work in grease fires or electrical environments, and fighting raging infernos required different skills and tactics than dousing a smoldering trash fire. In short, firefighting grew from an avocation to a science, and one of its laws stated that hesitation and bad decisions do more harm than good.

Clearly, firefighting shouldn't be left to the amateurs unless necessary and, in such cases, the devices they use should be as simple as possible.

With this in mind, a few companies have rekindled the centuries-old idea of the fire grenade, made it simple, nontoxic and eco-friendly, and dubbed it the throwable fire extinguisher. It comes in two basic forms: a breakable ampul about the size of a large shampoo bottle and a heat-activated ball roughly the size of a cantaloupe. Both are lightweight enough for even children, the elderly and the differently abled to throw or roll them.

Whereas throwable ampuls shatter and react with fire to generate smothering gases and foam, fire extinguishing balls go boom and scatter dry chemicals. As we'll shortly see, although they cover much of the same territory, their approaches differ quite a bit.

The Geometry of Fire

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]:

  • Class A: familiar combustibles, such as wood, cloth, paper, rubber and many plastics
  • Class B: flammable liquids (which burn at room temperature) and combustible liquids (which are defined as having a flash point at or above 100 F, or 37.8 C), including petroleum greases, oils, solvents, lacquers, alcohols and flammable gases
  • Class C: Class A or B fuels, combined with the tangy zip of energized electrical equipment
  • Class D: combustible metals, such as magnesium, titanium, zirconium, sodium, lithium and potassium (some of which tend to crop up in car fires)
  • Class K: cooktop and industrial fryer fires composed of the delicious-but-deadly things we cook food in, such as vegetable oil, animal oils and fats

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.

Great Balls (and Bottles) of Firefighting

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."

Author's Note: How do throwable fire extinguishers work?

I don't think I'm alone in feeling a certain anxiety when it comes to handling a fire extinguisher in an emergency, so I can definitely see the appeal of making the process as simple as possible. Of course, you still need to know what you're doing, which involves a bit of reading up but, hey, you read HowStuffWorks, right? You like learning how, um, stuff works.

One of the keys to fighting fires safely is to understand that you only have a small window of time in which to bring some sort of extinguishing device to bear. After that, matters are probably going to get far enough out of hand that you should really just get out and call 911. So, if grabbing a bottle or ball is faster than the fire extinguisher mantra of "Pull, Aim, Squeeze and Sweep," then maybe there's something to popping for a throwable or two.

Me, I'm going to wait until the fire authorities and chemists weigh in on them (the ones I contacted for this article either did not get back to me or declined to comment).

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Sources

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