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Flammability is how easily something will burn or ignite, causing fire or combustion. The degree of difficulty required to cause the combustion of a substance is quantified through fire testing. Internationally, a variety of test protocols exist to quantify flammability. The ratings achieved are used in building codes, insurance requirements, fire codes and other regulations governing the use of building materials as well as the storage and handling of highly flammable substances inside and outside of structures and in surface and air transportation. For instance, changing an occupancy by altering the flammability of the contents requires the owner of a building to apply for a building permit to make sure that the overall fire protection design basis of the facility can take the change into account.
A fire test can be conducted to determine the degree of flammability. Test standards used to make this determination but are not limited to the following:
- Underwriters Laboratories UL 94 Flammability Testing
- International Electrotechnical Commission IEC 60707, 60695-11-10 and 60695-11-20
- International Organization for Standardization ISO 9772 and 9773.
- National Fire Protection Association NFPA 287 Standard Test Methods for Measurement of Flammability of Materials in Cleanrooms Using a Fire Propagation Apparatus (FPA)
- NFPA 701: Standard Methods of Fire Tests for Flame Propagation of Textiles and Films
- NFPA 850: Recommended Practice for Fire Protection for Electric Generating Plants and High Voltage Direct Current Converter Stations
Categorization of building materials 
DIN 4102 B3: Polyurethane foam (easy to ignite = lots of hydrocarbon bonds usually)
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 as well as flammability:
|Rating||Degree of flammability||Examples|
|A1||100% noncombustible (nichtbrennbar)|
|A2||~98% noncombustible (nichtbrennbar)|
|B1||Difficult to ignite (schwer entflammbar)||intumescents and some high end silicones|
|B3||Easily ignited (leichtentflammbar)|
A more recent norm 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 which reduces the flammability of those materials.
Important characteristics 
Flash point 
A material's flash point is a metric of how easy it is to ignite the vapor of the material as it evaporates into the atmosphere. A lower flash point indicates higher flammability. Materials with flash points below 100 °F (38 °C) are regulated in the United States by OSHA as potential workplace hazards.
Vapor pressure 
- The vapor pressure of a liquid, which varies with its temperature, 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, with higher vapor pressures leading to lower flash points and higher flammability.
Examples of flammable substance 
Flammable substances include, but are not limited to:
- Gasoline / a complicated mixture of hydrocarbons that includes isomers of octane, C8H18
- Ethanol / CH3CH2OH
- Isopropanol / CH3CH(OH)CH3
- Methanol / CH3OH
- Acetone / CH3COCH3
- Nitromethane / CH3NO2
Examples of nonflammable liquids 
Classification of flammability 
The US Government uses the Hazardous Materials Identification System (HMIS) standard for flammability ratings, as do many US regulatory agencies, and also the US National Fire Protection Association (NFPA).
The ratings are as follows:
|Rating||Degree of flammability||Examples|
|0||Materials that will not burn||water|
|1||Materials that must be preheated before they will ignite||lubricating oils, cooking oils|
|2||Materials that must be moderately heated or exposed to relatively high ambient temperatures before they will ignite||diesel fuel|
|3||Liquids and solids that can ignite under almost all temperature conditions||gasoline, acetone|
|4||Materials which will rapidly vaporize at atmospheric pressure and normal temperatures, or are readily dispersed in air and which burn readily||natural gas, propane, butane|
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, because the fire load and smoke development in that one apartment would be so immense as to overtax the active fire protection as well as the 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 ordinarily enforced by the local fire prevention officer.
Flammable vs. inflammable 
|Look up flammable or inflammable in Wiktionary, the free dictionary.|
Flammable and inflammable both mean capable of burning. The word "inflammable" came from Latin inflammāre = "to set fire to," where the prefix "in-" means "in" as in "indoctrinate", rather than "not" as in "invisible" and "ineligible". Nonetheless, inflammable is often erroneously thought to mean "non-flammable". This safety hazard has been avoided by the use of flammable on warning labels referring to physical combustibility. In the United States the word inflammable has been largely abandoned in common, scientific, industrial, and written language. Antonyms of flammable/inflammable are non-flammable, non-inflammable, incombustible, non-combustible, uninflammable, or simply not flammable.
See also 
- Fire test
- Fire protection
- Active fire protection
- Passive fire protection
- Flammable liquids
- Lower flammable limit
- Upper flammable limit
- "INFLAMMABLE". Common Errors in English Usage. Washington State University. Retrieved 30 June 2012.