Combustibility

Combustible materials are those which can combust, i.e. burn in air. Flammable materials are combustible materials that can be easily ignited at ambient temperatures whereas those that are harder to ignite are just considered combustible. DIN4102 A1 noncombustible rockwoolDIN4102 A2 gypsum fireproofing plaster leavened with polystyrene beadsDIN 4102 B1 (difficult to ignite/often self-extinguishing) Silicone caulking used as a component in firestopping piping penetrationDIN 4102 B2: Timber, normal combustibilityDIN 4102 B3: Polyurethane foam (easy to ignite = many hydrocarbon bonds usually) Combustible materials are those which can combust, i.e. burn in air. Flammable materials are combustible materials that can be easily ignited at ambient temperatures whereas those that are harder to ignite are just considered combustible. The degree of flammability or combustibility in air depends largely upon the volatility of the material - this is related to its composition-specific vapour pressure, which is temperature dependent. The quantity of vapour produced can be enhanced by increasing the surface area of the material forming a mist or dust. Take wood as an example. Finely divided wood dust can undergo explosive combustion and produce a blast wave. A piece of paper (made from wood) catches on fire quite easily. A heavy oak desk is much harder to ignite, even though the wood fibre is the same in all three materials. Common sense (and indeed scientific consensus until the mid-1700s) would seem to suggest that material 'disappears' when burned, as only the ash is left. In fact, there is an increase in weight because the combustible material reacts (or combines) chemically with oxygen, which also has mass. The original mass of combustible material and the mass of the oxygen required for combustion equals the mass of the combustion products (ash, water, carbon dioxide, and other gases). Antoine Lavoisier, one of the pioneers in these early insights, stated that Nothing is lost, nothing is created, everything is transformed, which would later be known as the law of conservation of mass. Lavoisier used the experimental fact that some metals gained mass when they burned to support his ideas. 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 put forward the use of '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/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 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)—where combustible liquids have a flash point above 100 °F (38 °C). Flammable solids are solids that are readily combustible, or 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 is the ease with which a combustible substance can be ignited, causing fire or combustion or even an explosion. 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: Flammability of furniture is of concern as cigarettes and candle accidents can trigger domestic fires. In 1975, California began implementing Technical Bulletin 117 (TB 117), which required that materials such as polyurethane foam used to fill furniture be able to withstand a small open flame, equivalent to a candle, for at least 12 seconds. In polyurethane foam, furniture manufacturers typically meet TB 117 with additive halogenated organic flame retardants. No other U.S. states had similar standards, but because California has such a large market, manufacturers meet TB 117 in products that they distribute across the United States. The proliferation of flame retardants, and especially halogenated organic flame retardants, in furniture across the United States is strongly linked to TB 117. When it became apparent that the risk-benefit ratio of this approach was unfavorable and industry had used falsified documentation (i.e. see David Heimbach) for the use of flame retardants, California modified TB 117 to require that fabric covering upholstered furniture meet a smolder test replacing the open flame test. Gov. Jerry Brown signed the modified TB117-2013, which became effective in 2014.