The LWF Blog

Fire Safety for Facilities Management Personnel – How Fire Works – Part 57

August 3, 2020 1:06 pm

Lawrence Webster Forrest (LWF) is a specialist fire engineering and fire risk management consultancy whose aim is to give information on best practice in fire safety for facilities management personnel through this blog series. In part 56, LWF looked at the combustion of solid materials and in part 57, we continue by discussing the combustion of flammable liquids.

Flammable liquids vary considerably in terms of their combustibility. Consider olive oil and cooking oil, both of which would require the application of a lot of heat in order to ignite. In this way, they act more similarly to solids. These oils are combustible but relatively stable and do not pose a greater fire risk than the presence of a combustible solid. It should be noted that cooking oils can be ignited more easily if they are absorbed into a wick and lit in a way that is comparable to a candle being lit with a match.

White spirit and paraffin would need much less heat applying before they released enough vapour to combust. Liquids such as these should be considered flammable and this is usually indicated on the containers they are kept in. Flammable liquids pose a greater hazard than combustible liquids.

Petrol and ether produce enough vapour even at normal room temperature to be ignited by a spark. These liquids are particularly hazardous and special precautions must be taken to ensure the vapour produced is not exposed to a form of ignition. Fairly obviously, this is why smoking is not allowed in petrol stations.

A way to measure how hazardous a flammable liquid might be is to establish its ‘flashpoint’. The flashpoint is the minimum temperature during a test that the liquid gives off sufficient vapour to ignite. The higher the flashpoint, the less hazardous it is.

The flashpoint of many cooking oils exceeds 200 ºC. The flashpoint of petrol is around -43 ºC. Most other flammable liquids will fall between those two levels.

The flashpoint of a flammable liquid is usually marked on its container. The Classification, Labelling and Packaging of Chemicals (Amendments to Secondary Legislation) Regulations 2015, known as the CLP Regulations, (PDF), gives information on how hazards should be indicated on packaging.

It is important that any flammable liquids are stored correctly and ventilation appropriately and quantities used in the workplace must be limited.

In part 58, LWF will continue looking at flammable liquids. In the meantime, if you have any queries about your own facilities or wish to discuss this blog series, please contact LWF on freephone 0800 410 1130.

Lawrence Webster Forrest is a fire engineering consultancy based in Surrey with over 25 years’ experience, which provides a wide range of consultancy services to professionals involved in the design, development and construction and operation of buildings.

While care has been taken to ensure that information contained in LWF’s publications is true and correct at the time of publication, changes in circumstances after the time of publication may impact on the accuracy of this information.