Essential Oil Flash Point

Why would I need to know about the flash point of an essential oil?  It is not something that I think about in my day to day work as an aromatherapist, although I do follow the ‘golden rule’ as much as possible of keeping all my oils in a cool, dark place. has this definition of a flash point:

Temperature at and above which a liquid gives off enough flammable vapor to form a mixture with air that can be ignited by contact with a hot surface, spark, or flame. Lower the flash point, greater the fire hazard. Common test methods of determining flash point include Pensky-Marten Closed Tester (ASTM D93-79), Setaflash Closed Tester (ASTM D3278-78), and Tag Closed Tester (ASTM D56-79). Since each test method may yield a different reading, the test method employed is usually indicated when a liquid’s flash point is given in a material safety data sheet (MSDS) or in technical documents.

The flash point should not be confused with auto-ignition point temperature at which combustion occurs spontaneously, without an external source of ignition.

As you can see for this, knowing what the flash point of an essential oil is could certainly be important when we are looking at how we store and transport them.  If you are going to be storing and transporting large amounts of essential oils it would be important to have a Material Safety Data Sheet for each oil.  Most Essential Oil Suppliers should be able to provide their clients with an MSDS for each of the oil that they carry and an MSDS might actually accompany a shipment.  Here is an example of what you can expect to see on a MSDS.  This one is available online and is from New Directions Aromatics for Sweet Orange.

Although most of us don’t work with our essential oils over an open flame, or near sparks and hot surfaces, keeping in mind that doing this could be hazardous is something all of us should keep at the back of our minds.  For instance if you are using an open flame candle diffuser care should be taken not to pour essential oil onto the flame, simple common sense really.

The auto-ignition point of an essential oil is, as mentioned above different to the flash point.  I haven’t been able to find much information as to when an essential oil might spontaneously burst into flame, but over the years I have heard of a few incidence where under heat this has happened.  One incident was about an aromatherapist who, after working with clients all day, giving essential oil massages, had her ‘dirty linen’ in the truck of her car.  The car stood outside in very hot conditions and the linen apparently burst into flame.  I have also heard of a few incidences when people using essential oils on items in a dryer had them burst into flame.  I don’t have any information on how hot the temperature and to be, or how long it took for this to happen, nor do I know how much essential oil was actually involved, but once again if we keep anything that has essential oil, or essential oil residues in a cooler environment we shouldn’t have to worry about auto-ignition.

When I was looking around at what others had to say about essential oils and their flash points, I did come across a number of soap making sites that defined the flash point of an essential oil as the temperature at which the essential oil dissipates in soap making.  However as we have seen from the above definition, this is not what a flash point is.  When considering when the essential oil might dissipate in soap making it would be better to use the boiling point of the essential oil.  The flash point of an essential oil i.e. when it can ignite when exposed to an open flame or spark, is generally a much lower temperature than the boiling point of the same essential oil.  One source I looked at suggested that most essential oils have a boiling point of over 300°F.   I don’t make soap myself so I will take their word for it.

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