Combustibility and flammability


A combustible material is a material that can burn in air under certain conditions. A material is flammable if it ignites easily at ambient temperatures. In other words, a combustible material ignites with some effort and a flammable material catches fire immediately on exposure to flame.
The degree of flammability in air depends largely upon the volatility of the material 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. Take wood as an example. Finely divided wood dust can undergo explosive flames and produce a blast wave. A piece of paper 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 would seem to suggest that material "disappears" when burned, as only the ash is left. Further scientific research has found that conservation of mass holds for chemical reactions. Antoine Lavoisier, one of the pioneers in these early insights, stated: "Nothing is lost, nothing is created, everything is transformed." The burning of a solid material may appear to lose mass if the mass of combustion gases is not taken into account. The original mass of flammable material and the mass of the oxygen consumed equals the mass of the flame products. Lavoisier used the experimental fact that some metals gained mass when they burned to support his ideas.

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 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" 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 less-vigorously burning materials are combustible. For example, in the United States flammable liquids, by definition, have a flash point below —where combustible liquids have a flash point above. 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 and combustible liquids between and.

Flammability

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.

Classification of flammability

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.
CategoryCategory 1Category 2Category 3Category 4
Flash point<<≥ - ≤> - ≤
Boiling point≤>
Example liquidsGasoline, Diethyl etherEthanol, Isopropyl alcoholKerosene, 1-ButanolDiesel fuel, Formic acid
GHS signal word and hazard statementDanger - Extremely flammable liquid and vaporDanger - Highly flammable liquid and vaporWarning - Flammable liquid and vaporWarning - Combustible liquid

Prior to 2012, OSHA's classification of flammable and combustible liquids in regulation 1910.106, was nearly identical to the National Fire Protective Association 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 specialist applications, such as NFPA 704, which uses five categories, 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 American Coatings Association's Hazardous Materials Identification System and Lab Safety Supply's Hazardous Material Identification Guide.

Examples of flammable substances

Flammable substances include, but are not limited to:
Flammability of furniture is of concern as cigarettes and candle accidents can trigger domestic fires. In 1975, California began implementing Technical Bulletin 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 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.

Fabric flammability

Lightweight textiles with porous surfaces are the most flammable fabrics. Wool is less flammable than cotton, linen, silk, or viscose. Polyester and nylon resist ignition, and melt rather than catch fire. Acrylic is the most flammable synthetic fiber.

Testing

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:
Combustibility is a measure of how easily a substance bursts into flame, through fire or combustion. This is an important property to consider when a substance is used for construction or is being stored. It is also important in processes that produce combustible substances as a by-product. Special precautions are usually required for substances that are easily combustible. These measures may include installation of fire sprinklers or storage remote from possible sources of ignition.
Substances with low combustibility may be selected for construction where the fire risk must be reduced, such as apartment buildings, houses, or offices. If combustible resources are used there is greater chance of fire accidents and deaths. Fire resistant substances are preferred for building materials and furnishings.

Non-combustible material

A non-combustible material is a substance that does not ignite, burn, support combustion, or release flammable vapors when subject to fire or heat, in the form in which it is used and under conditions anticipated. Any solid substance complying with either of two sets of passing criteria listed in Section 8 of ASTM E 136 when the substance is tested in accordance with the procedure specified in ASTM E 136 is considered to be non-combustible.