Question

The fire extinguisher 'Pyrene' contains-
(A) Carbon dioxide
(B) Carbon disulphide
(C) Carbon tetrachloride
(D) Chloroform

Answer 1

Hint An attempt to this question can be made by determining the properties of pyrene used in fire extinguishers. Now compare the characteristics of the compounds mentioned in the options with the properties of pyrene. Based on this you can determine the composition of pyrene.

Complete step by step solution:
- A fire extinguisher is an equipment that is used to control or extinguish small fires in emergency situations.
- The Pyrene Company Limited was the company that manufactured the fire extinguisher 'Pyrene'.
- The company pioneered the use of carbon tetrachloride (CTC) to extinguish or control fires. Carbon tetrachloride is an organic compound which has a chemical formula of $CC{l}_4$. It is a colourless liquid with a sweet smell.
- Let us now look into what chemical reaction actually happens when Pyrene is used on a fire. It worked on the principle that the fire will go out in the absence of oxygen. $CC{l}_4$ creates a dense, $O_2$ excluding blanket of fumes when it was sprayed onto the fire as it is not flammable.
- The disadvantage is that when $CC{l}_4$ is heated to decomposition, it will emit extremely toxic fumes of phosgene ($COC{l}_2$) and hydrogen chloride (HCl).
- Hence the correct answer is option (C) Carbon tetrachloride.

Additional Information:
- The vapours of carbon tetrachloride was discovered to be extremely toxic. Hence, Pyrene extinguishers were withdrawn in the late 1950s.
- $CC{l}_4$inhalation by humans leads to short term effects like nausea, vomiting, and headaches. Prolonged exposure to $CC{l}_4$ causes acute liver damage, kidney damage, and also damages the central nervous system.

Note: It is important to know the way pyrene fire extinguisher works. Unlike common fire extinguishers, the carbon tetrachloride present in pyrene forms a protective layer around the area of the fire. This layer prohibits the supply of oxygen and thus helps to control the fire.