Spontaneous combustion of linseed oil
How this fire happened
This fire occurred in a Church undergoing refurbishment, after a contractor left a pile of linseed oil soaked rags in a bin overnight.
The rags had just been used to apply the linseed oil as a sealer to some flooring.
The fire was caused by an exothermic chemical reaction within the rags, which eventually led to flaming combustion, which spread to a container of white spirit stored close by.
Rags soaked with linseed oil (especially when stored in a restricted space where any heat produced cannot dissipate) are a known fire hazard.
This is because they provide a large surface area for the evaporation and oxidation of the oil.
Linseed oil evaporates very rapidly causing an exothermic reaction, which accelerates as the temperature of the rags increases.
When the accumulated heat exceeds the rate of heat dissipation, the temperature increases and may eventually become hot enough to cause the rags to spontaneously combust.
Whilst this fire was caused by linseed oil, there are other oils that can also create a similar hazard - especially when heated on radiators and other similar hot surfaces.
A number of fires have occurred in vehicle workshops when oily cloths and towels have been discarded into enclosed bins.
Some other similar incidents that East Sussex Fire & Rescue Service has attended have included: a fire in a stack of tea towels that had just been laundered and tumble dried and another incident where a householder had used a linseed oil soaked rag to seal a hardwood door sill - where the rag caught fire later that night when it was stored in a plastic box under the kitchen sink.
In both the above examples it was fortunate that a working smoke alarm was fitted that gave early warning and prevented serious damage or injury.
Three conditions which determine whether or not an oxidation reaction will cause dangerous heating are:
rate of heat generation,
air supply, and
insulation properties of the immediate surroundings.
When exposed to the atmosphere, organic substances capable of combination with oxygen will oxidize at some critical temperature with the evolution of heat.
The rate of oxidation at normal temperatures is usually so slow that the released heat is transferred to surroundings areas as rapidly as it is formed, with no increase in temperature of the material (did you know that rusting metal generates heat! - albeit very small amounts that rapidly dissipate).
However this is not the case with Linseed and some other oils - which generate heat much more rapidly than can be dissipated, with a resulting temperature increase in the material.
In order for spontaneous ignition to occur, there must be sufficient oxygen available for the reaction to proceed, but not so much draft that the heat is carried away as quickly as it is generated.
For example, a linseed oil-soaked rag may heat spontaneously in the bottom of a container, but would not do so if hung on a clothesline where air movement would remove the heat as quickly as it was formed.
Because of the many possible combinations of air supply and insulation, it is impossible to predict with certainty whether or not a material will heat spontaneously.
East Sussex Fire & Rescue Service would advise that oil soaked rags are not stored inside a building and the following methods of safe disposal are considered:
Hang the rag out to dry on a washing line first before disposing of in your rubbish bin.
Soak the rag in water and seal in a plastic bag before disposal in your rubbish bin
Storing in an air tight (preferably metal) container.
If safe - controlled burning.
Fire warning over self combusting essential oils
The number of fires caused by fabrics stained with essential oils has increased, Wiltshire Fire and Rescue Service has said.
WFRS said fires were caused when people washed oil stained fabrics on or below 40 degrees and then put them away in a warm place.