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"Chemical Fire-extinguisher." Patent no. 28996, filed by Edward J. Ennis, 1888

 

Patent no. 28996. Filing year 1888.

"Chemical Fire-Extinguisher," Edward J. Ennis.

For centuries, fire fighting consisted of little more than bucket brigades. That all changed in 1666, when the great fire of London destroyed close to 13,000 buildings and prompted the development of better fire-fighting equipment. Hand-operated pumping wagons were devised and remained the standard until the 19th century, when a number of key inventions -- including pressurized water hoses, steam-powered fire wagons, fire alarms and fire extinguishers -- revolutionized fire fighting.

The first fire extinguisher was invented in 1813 by George Manby, a former British militiaman who had noticed the challenges faced by fire fighters in dousing the top floors of burning buildings. His extinguisher consisted of a four-gallon copper vessel containing three gallons of water and one gallon of compressed air, which forced the water out of the base of the cylinder when a valve was opened.

It was a challenge to maintain the air pressure in Manby's extinguisher over long periods of time. In 1866, Frenchman François Carlier invented a chemical means of creating pressure when needed. His cylinder contained a mixture of water and bicarbonate of soda along with a sealed bottle of sulphuric acid. When the bottle was punctured, the acid and soda reacted, and the resulting carbon dioxide forced the water out of the nozzle.

These acid-soda extinguishers required an opening in the cylinder to insert and replace the bottle of acid. A flaw common to extinguisher designs, noted Edward Ennis of Montréal in his 1888 patent description, was "the escape, through the opening, of the gas generated, lessening the pressure at the point of delivery." Ennis claimed that his design -- a rubber-ringed cap that screwed tightly into the rim of the cylinder -- was gas-tight. A handle extended through the cap and into the stopper in the bottle of acid. Drawing up the handle removed the stopper and started the reaction.

Extinguisher containers seem to have posed a common design challenge; a range of Canadian patents -- including no. 3330 and no. 21627 -- were filed to improve on them. Carlier's chemistry, though, has stood the test of time and even expanded in usefulness. Not only is carbon dioxide still used as a pressurizing agent in some extinguishers, but because it does not burn and is heavier than air, the compound has become a key fire-fighting component itself. Its heaviness enables it to blanket a fire, starving the flame by preventing oxygen from reaching the burning material.

References

"Fire Extinguisher." World of Invention. Edited by Kimberly A. McGrath. Detroit, Mich.: Gale Research, 1999, p. 249.

"Fire-Fighting Equipment." World of Invention. Edited by Kimberly A. McGrath. Detroit, Mich.: Gale Research, 1999, p. 250.

Sickler, Leighton. "Our Invisible Friend - CO2" Chemistry Hall of Fame.
www.chem.yorku.ca/hall_of_fame/essays95/CarbonDioxide/CarbonDioxide.htm (accessed October 25, 2005).