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| title | chunk | source | category | tags | date_saved | instance |
|---|---|---|---|---|---|---|
| Combustibility and flammability | 3/3 | https://en.wikipedia.org/wiki/Combustibility_and_flammability | reference | science, encyclopedia | 2026-05-05T10:52:07.365620+00:00 | kb-cron |
=== Flammability or explosive range === The lower flammability limit or lower explosive limit (LFL/LEL) represents the lowest air to fuel vapor concentration required for combustion to take place when ignited by an external source, for any chemical. Any concentration lower than this could not produce a flame or result in combustion. The upper flammability limit or upper explosive limit (UFL/UEL) represents the highest air to fuel vapor concentration at which combustion can take place when ignited by an external source. Any fuel-air mixture higher than this would be too concentrated to result in combustion. The values existing between these two limits represent the flammable or explosive range. Within this threshold, given an external ignition source, combustion of the particular fuel would likely happen.
=== Vapor pressure === The vapor pressure of a liquid is a measure of how much the vapor of the liquid tends to concentrate in the surrounding atmosphere as the liquid evaporates. Vapor pressure is a major determinant of the flash point and flame point, with higher vapor pressures leading to lower flash points and higher flammability ratings.
== Codes ==
The International Code Council (ICC) developed fire code requirements to provide adequate protection to a building and its occupants. These codes specify the combustibility rating for materials, the entrance and exit requirements, active fire protection requirements, and numerous other things. In the U.S., other agencies have also developed building codes that specify combustibility ratings. Following the requirements of these fire codes is crucial for higher occupancy buildings.
For existing buildings, fire codes focus on maintaining the occupancies as originally intended. In other words, if a portion of a building were designed as an apartment, one could not suddenly load it with flammable liquids and turn it into a gas storage facility. The fire load and smoke development in that one apartment would be so immense it would overtax the active and passive fire protection means for the building. The handling and use of flammable substances inside a building is subject to the local fire code, which is enforced by the local fire prevention officer.
== Fire service relevance == Understanding combustibility and flammability is important for fire service operations. Flammable materials, like gasoline, produce vapors that can ignite at low temperatures. This can contribute to rapid fire spread, even to remote locations. Combustible materials, like wood, require a higher temperature to ignite, but will burn longer once it reaches that temperature. Knowing what materials are present in a building is very important for firefighters. Knowing whether a material is flammable or combustible can help firefighters know what to expect as far as fire behavior and how quickly the fire may spread. Buildings with flammable liquids or gases would be at a higher risk for a quick growing fire with a lot of heat early on. Buildings storing combustibles may have a lower rate of spread, but can sustain burning longer. There are many different factors that influence how materials will burn. Moisture, surface area, and the ventilation in the area are a few factors, as well as, flash points and ignition temperatures. Armed with knowledge like the flash point and whether it is considered flammable or combustible helps firefighters predict fire behavior and use the correct suppression methods. This increases scene safety overall.
=== Fire testing ===
Various countries have tests for determining non-combustibility of materials. Most involve the heating of a specified quantity of the test specimen for a set duration. Usually, the material must not support combustion and must not lose more than a specified amount of mass. As a general rule of thumb, concrete, steel, and ceramics - in other words inorganic substances - pass these tests. Building codes list them as suitable and sometimes mandate their use in certain applications. In Canada, for instance, firewalls must be made of concrete.
== Categorization of building materials ==
Materials can be tested for the degree of flammability and combustibility in accordance with the German DIN 4102. DIN 4102, as well as its British cousin BS 476 include for testing of passive fire protection systems, as well as some of its constituent materials. The following are the categories in order of degree of combustibility and flammability:
A more recent industrial standard is the European EN 13501-1 - Fire classification of construction products and building elements—which roughly replaces A2 with A2/B, B1 with C, B2 with D/E and B3 with F. B3 or F rated materials may not be used in building unless combined with another material that reduces the flammability of those materials.
== See also == Explosive material, reactive substance that contains a great amount of potential energy that can produce an explosion Fire test, means of determining whether fire protection products meet minimum performance criteria Fire protection, any measure to prevent or limit damage from fire Flammability limit, burning within well-defined lower and upper bounds Ultrafine particle, particulate matter under 100 nm in diameter
== Notes ==
== References ==
== External links ==
Fire Performance of Ageing Cable Compounds, NFPA Treatise by Perry Marteny CAN4-S114 CAN/ULC-S114 Abstract "Combustible Dust: Agricultural Related Fires and Explosions Increasing, but Preventable" Division of Occupational Safety and Health, N.C. Department of Labor Combustible Dust: A Major Hot Work Hazard" Division of Occupational Safety and Health, N.C. Department of Labor