3.4 Fixed and portable fire-fighting equipment

Question 1

Classes of fire

Answer 1

Class A carbonaceous solidsClass B flammable liquids Class C gas Class D metal Class F fats and cooking oils Electrical

Question 2

methods of extinguishing fire can be classified as:

Answer 2

 Starvation – limiting fuel  Smothering – limiting oxygen  Cooling – limiting heat.

Question 3

Starvation Fires can be starved of fuel in three ways:

Answer 3

 By removing potential fuel from the vicinity of the fire, for example, by draining fuel from burning tanks.  By removing the fire from the mass of combustible material, for example, pulling apart a burning haystack.  By dividing the burning material into smaller fires.

Question 4

Smothering Smothering works by

Answer 4

preventing fresh air reaching the seat of the fire, and thus allowing combustion to reduce the oxygen content in the confined atmosphere until it extinguishes itself.

Question 5

Cooling Combustion will stop as soon as

Answer 5

the rate of cooling exceeds the rate of heat generated by the combustion process. Cooling the fuel is the main way in which water is used to extinguish fires.

Question 6

Extinguishing media

Answer 6

Water Red fires of a general nature ineffective against fires involving liquid fuelsFoam Cream liquid fuel firesCarbon dioxide and inert gases BlackDry chemical powders BlueVaporising Liquid GreenWet chemical yellow cooking oils and fats

Question 7

As the action of the sprinklers is likely to reduce the rate of burning of a fire and the mass smoke flow, there are number of possible benefits to building designers, including: 4

Answer 7

 the travel distance to an exit can potentially be increased, without reducing the level of people’s safety  building compartment areas/volumes may be increased, compared to similar buildings without sprinklers  fire resistance levels of structural components may be reduced  the separating distance between buildings may be reduced by one half.

Question 8

The capability of a sprinkler system is designed to match the type of risk with which it will have to cope. There are three main hazard classifications based on:  the expected fuel load of the premises  the rate of fire growth expected from the contents or processes. These are:

Answer 8

Light hazard Low combustible loading, with a slow rate of fire growth Ordinary hazard Low to moderate combustible loading, with moderate to fast rate of fire growth High hazard High combustible content, with fast to ultra-fast rate of fire growth

Question 9

The owners of a large distribution warehouse business have secured a contract from a stationery manufacturer. Their insurers have recommended that the proposed storage facility is sprinkler protected. Outline the factors to be considered in providing an adequate sprinkler system for the storage facility. 10 marks

Answer 9

An initial design factor to be considered in the provision of an adequate sprinkler system would be the capacity of water required, the existence of an adequate and assured water supply and the availability of an alternative if this was to fail for any reason. The design of the pumping system would also be important with a diesel back up if the decision was taken to install electrically operated pumps. Other factors would include:  the means of activating the system (frangible bulbs or detector activated)  the linkage of the system to alarms  the spray pattern required  the area to be covered and the presence of other combustibles apart from the stationery  the height of the storage racks and their distance from the sprinkler heads, with a decision to be taken on the need for in-rack sprinkling  the provision of fire stopping for sprinklers passing through compartmentalisation  the provision of fire water run off  the arrangements to be put in place for testing the equipment  issues concerned with the protection of the sprinkler heads and the electrical system.