The fire point is the temperature at which a liquid will produce enough flammable vapor to create sustained combustion, burning for at least five seconds, if the vapor is exposed to flame or a spark. It is an important parameter for safety testing, as the combustion of a fluid can create a fire risk if the flames jump to objects in the surrounding area or ignite other fluids. Safety testing for liquids known to be potentially flammable can include a test to determine the fire point.
A number of related terms refer to the flammability of fluid components, and it is important to be aware of the differences between them. As temperatures rise, fluids produce flammable vapors through the process of evaporation. At the flash point, exposure to a point of ignition like an open flame will produce a brief flash of flame, but the temperature is not hot enough to perpetuate the evaporation and maintain the flames. The fire point, slightly higher, provides sustained ignition. At the auto-ignition point, temperatures rise enough for the vapor to catch fire spontaneously, a considerable safety risk.
In a system where potentially flammable fluids are in use, ranging from lubricants to fuels, the fire point is an important safety consideration. Operators must consider the potential maximum temperature of the system when selecting fluids they will use it in, as they do not want to create safety hazards. If a lubricant will burst into flames when exposed to a spark at the normal operating temperature, for example, it would not be suitable.
Companies developing potentially flammable fluids can perform materials testing to learn more about their properties. This can include controlled testing to find the flash, fire, and auto-ignition points for the purpose of publishing safety information. The company will also check for toxins that could pose a threat to human health, corrosiveness, and other properties known to be potential issues.
Information about the fire point is not always available. As a general rule of thumb, it falls around 50 degrees Fahrenheit (10 degrees Celsius) above the flash point. If there are specific concerns about sustained combustion in high temperatures, a separate test should be performed to confirm the fire point and determine whether a flammable fluid is suitable for use. This can be done by a materials testing company, where a controlled environment for testing is available to obtain reliable and highly accurate results.
By Mary McMahon
Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a About Mechanics researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.