Carbon Tetrachloride (CCl4), a halogenated hydrocarbon in the form of a non flammable organic liquid has special fire extinguishing properties. It was generally less effective than other alternatives from the same era, but being inexpensive was the most popular.
It extinguishes fire partly by the displacement of air when in the form of a heavier than air inert vapour cloud, but mainly by inhibiting the chain reaction of combustion (affinity for free radicals, etc). It's inhibitory factor is 10% (i.e. requires a 10% concentration in air to prevent combustion).
The liquid is clear, heavy, volatile & 5.3 times denser than air & non-conductive, boiling at 77 C.
To be effective the liquid must vapourise in the fire zone & the hand pumps suffered from discharge in a jerky solid jet, with most CTC running off without vapourising - CTC was best discharged as a spray dissolved & propelled by CO2, a method pioneered in 1911 by Read & Cambell using sparklet bulbs ('Petrolex') in the followed in the 1920's by J.Blakeborough (later to form Nu-Swift) who pioneered stored pressure charges. Despite this pump extinguishers were still widely manufactured into the 1960's with the Pyrene Company of Delaware pioneering the use of CTC with their first pump in 1907.
CTC was widely used as a degreasing & dry cleaning solvent and theft from hand pumps was not unknown with large users like the War Department adding a pink dye to the liquid to deter theft for cleaning of clothing.
CTC was narcotic & its by products when used on fires were equally dangerous in some cases Phosgene was formed, a gas used as a weapon in World War 1
In the 1930's & 40's Methyl Bromide was developed by the National Fire Protection Company and gave CTC a run for it's money being adopted by widely by the Air Ministry for portable & fixedmilitary planes and electricity boards for fixed systems in substations as it had a far lower inhibitory factor of 4. It rapidly fell out of favour due to it's prohbitive cost & the key property of MB that made it an excellent choice in ship fumigation.....
The Third Reich provided the next step in vapourising liquid technology by developing ChloroBromoMethane during World War 2, the technology being initially seized by the US and filtering through to the UK by the mid 1950's via Nu Swift. Although more expensive than CTC it was less toxic & more effective with an inhibitory factor of 6.2.
The early 1960's saw an advance in the UK when Nu Swift developed a blend of 111 Trichloroethane & ChloroBromoMethane (80%/20%) branded Uni Flash liquid, being a cheaper alternative to CBM whilst retaining low toxicity and a good inibitory factor.
The end of the 60's saw ICI develop the vapourising liquid we all know, Bromochlorodifluoromethane, and BCF's handy properties ensured it's place in the forefront of fire fighting for the next 30 years & if it wasn't for the environmental concerns it would still be used widely today
