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| title | chunk | source | category | tags | date_saved | instance |
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| Combustibility and flammability | 1/3 | https://en.wikipedia.org/wiki/Combustibility_and_flammability | reference | science, encyclopedia | 2026-05-05T10:52:07.365620+00:00 | kb-cron |
A combustible material is a material that can burn (i.e. sustain a flame) in air under certain conditions. A material is flammable if it ignites easily at room temperature. In other words, a combustible material takes more effort to ignite and a flammable material ignites almost immediately when exposed to a flame. The degree of flammability in air depends largely on how easy the material vaporizes. This is related to its composition-specific vapor pressure, which is temperature dependent. The quantity of vapor produced can be enhanced by increasing the surface area of the material, forming a mist or dust. Wood is an example. Finely divided wood dust can undergo explosive flames and produce a blast wave. A piece of paper (made from pulp) catches on fire quite easily. A heavy oak desk is much harder to ignite, even though the wood fibers are the same in all three materials. Common sense, and scientific consensus until the mid-1700s, suggests that material disappears when burned, as only the ash is left. Further scientific research has found that conservation of mass holds for chemical reactions. The burning of a solid material may appear to lose mass if the mass of combustion gases (such as carbon dioxide and water vapor) is not taken into account. The original mass of flammable material and the mass of the oxygen consumed (from the surrounding air) equals the mass of the flame products (ash, water, carbon dioxide, and other gases). Some metals gain mass when they burn to support the idea (because those chemical reactions capture oxygen atoms into solid compounds rather than gaseous water).
== Definitions == Historically, flammable, inflammable and combustible meant capable of burning. The word "inflammable" came through French from the Latin inflammāre = "to set fire to", where the Latin preposition "in-" means "in" as in "indoctrinate", rather than "not" as in "invisible" and "ineligible". The word inflammable may be erroneously thought to mean non-flammable. The erroneous usage of the word inflammable is a significant safety hazard. Therefore, since the 1950s, efforts to use flammable in place of inflammable were accepted by linguists, and it is now the accepted standard in American English and British English. Antonyms of flammable or inflammable include: non-flammable, non-inflammable, incombustible, non-combustible, not flammable, and fireproof. Flammable applies to combustible materials that ignite easily and thus are more dangerous and more highly regulated. Less easily ignited and less-vigorously burning materials are combustible. For example, in the United States flammable liquids, by definition, have a flash point below 100 °F (38 °C). Combustible liquids have a flash point above 100 °F (38 °C). Flammable solids are solids that are readily combustible, may cause, or contribute to fire through friction. Readily combustible solids are powdered, granular, or pasty substances that easily ignite by brief contact with an ignition source, such as a burning match, and spread flame rapidly. The technical definitions vary between countries so the United Nations created the Globally Harmonized System of Classification and Labeling of Chemicals, which defines the flash point temperature of flammable liquids as between 0 and 140 °F (60 °C) and combustible liquids between 140 °F (60 °C) and 200 °F (93 °C).
== Flammability == Flammability is the ease with which a combustible substance can be ignited causing fire, combustion, or an explosion. The degree of difficulty required to cause the combustion of a substance is quantified through fire testing. A variety of test protocols exist to quantify flammability. The ratings achieved are used in building codes, insurance requirements, fire codes, and other regulations that govern the use of building materials as well as the storage and handling of highly flammable substances. This includes 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 of the facility takes the change into account.
=== Classification of flammability === Globally Harmonized System of Classification and Labelling of Chemicals uses a four category system to classify flammable liquids using flash point and boiling point temperature. This system is used internationally to evaluate and sort substances in industrial applications, workplaces and products distributed to consumers.
Prior to 2012, OSHA's classification of flammable and combustible liquids in regulation CFR 1910.106, was nearly identical to the National Fire Protection Association (NFPA) Flammable and Combustible Liquids Code, NFPA 30. While no longer used for occupational regulations, NFPA 30's definitions are still commonly used in fire codes and NFPA codes and standards.
Other systems for classifications of flammable liquids exist for more specialized applications, such as NFPA 704, which uses five categories. This is intended for emergency workers to understand the hazard posed by a substance during an emergency, such as a spill. In addition to GHS, flammability classifications are incorporated into various systems designed for communicating physical and health hazards in workplaces; such as the American Coatings Association's Hazardous Materials Identification System (HMIS)
=== Examples of flammable substances === Flammable substances include, but are not limited to:
Gasoline - Petrol / a complicated mixture of hydrocarbons that includes isomers of octane, C8H18 Ethanol / CH3CH2OH Rubber Isopropyl alcohol / CH3CH(OH)CH3 Methanol / CH3OH Wood Acetone / CH3COCH3 Paper Nitromethane / CH3NO2
=== Examples of nonflammable substances === Water Carbon tetrachloride Iron Ceramic