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Stain Rags and House Fires

July 8, 2011

I can’t tell you how many times I’ve fought or investigated fires where someone was staining woodwork and did not take care of the stain rags properly.  We responded to one of these last week.  We’ve been to homes under construction, homes just ready to be moved into, and homes undergoing renovation where someone did not dispose of stain rags properly and the house was destroyed.

Certain animal and vegetable oils will break down under the correct circumstances.  This breakdown causes an exothermic reaction (it releases heat).  As more heat is released, the breakdown process is speeded up and even more heat is released.  If there is adequate fuel, insulation, and ventilation, this process can break into open flaming combustion.

In the old days this was called spontaneous combustion.  We know the process is not spontaneous; rather it is a process that follows normal laws of chemistry.  Terms like ‘auto-ignition’ or ‘self-heating’ are more appropriate.

This process only works with animal and vegetable oils.  Mineral oils (like motor oil) don’t break down and build up heat the way animal and vegetable oils do.  However, if stain rags are thrown in with motor oil soaked rags, the stain rag can cause ignition and the motor oil can accelerate the fire.

Many woodworking stains are made with vegetable oils (like linseed oil).  I’m a wood worker and these stains are great products.  The user just needs to remember the hazard when applying these products.  A cotton rag used to apply stain has the perfect surface area-to-mass ratio to run this exothermic reaction clear to ignition.  One author* had 100 ml of stain (just over three ounces) in rags catch fire in five hours.  In some cases, stain rags have set for days before igniting.

Stain manufacturers are aware of this hazard.  That’s why these products have consumer warning labels on how to dispose of stain rags properly.

I cannot emphasize enough how important it is for you to read these instructions and follow them to the letter.  Many manufacturers advocate soaking the rags in water and letting them dry outside (NOT in a clothes dryer).  Manufacturers use different oils, so disposal measures will be unique to each product.  The manufacturer has performed testing on their product.  They know what it takes to avoid a fire with their product and their specific instructions must be followed to protect your home.

So please read the directions and follow them explicitly.  That will help ensure our trucks stay parked in the stations, rather than parked in front of your house.


* DeHaan, J. D. (2002).  Kirk’s fire investigation, Upper Saddle River, NJ:  Prentice Hall.


From → Fire Prevention

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