Safety Services


Working with flammable chemicals

Many chemicals are flammable depending on the environmental conditions. Understanding when these conditions are met is needed to work safely.


The lowest temperature at which the vapours of a volatile material will ignite in air ( 20.95% oxygen) if given an ignition source.

Fire point
The temperature at which the vapour will continue to burn after the ignition source has been stopped (usually higher than the flashpoint)​.

Flammability limit
The concentration between which (upper and/or lower limits) upper or lower the gaseous or vaporized substance at a fixed temperature and pressure can lead to flame propagation, detonation or an explosion. ​ 


​Flammable Flashpoint: equal to or higher than (≥) 230C (73.40F) and lower or equal to (≤) 600C (1400F)​

Highly Flammable Flashpoint: lower than (<) 230C and a boiling point higher than (>) 350C (950F)​

Extremely Flammable Flashpoint: lower than (<) 230C and a boiling point lower than (≤) 350C​

Non-flammable chemicals

Concentrations outside both limits are considered to be non-flammable. Flammability limits vary with temperature and pressure. However, the normal expression is in terms of % of volume at 25 °C at 1013.25mbar (mean sea-level atmospheric pressure (MSLP)). ​

​This information can be found on the Safety Data Sheet (SDS) for the substance​.

Flammable chemicals

Flammable signage
Any work with flammable chemicals may affect the fire risk assessment for the laboratory or even the building. For further information please read the relevant fire technical notes. The standard fire extinguisher for UCL is water mist and this may not be suitable for some chemicals.

All chemicals known to be flammable will display this symbol. 

Last updated: Thursday, September 30, 2021

Explosion risk

UCL does not usually carry out production type chemistry, in either the quantities used or the length of time to produce an explosive atmosphere in the workspace. If you think the risk of explosion is possible, please read further information on the DSEAR page.