Combustibility and flammability
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Acombustiblematerial is a material that can burn (i.e., sustain aflame) in air under certain conditions. A material isflammableif 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-specificvapour pressure,which is temperature dependent. The quantity of vapour produced can be enhanced by increasing thesurface areaof the material forming a mist or dust. Take wood as an example. Finely dividedwood dustcan undergoexplosive flamesand produce a blast wave. A piece of paper (made fromwood) 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 indeedscientific consensusuntil the mid-1700s) would seem to suggest that material "disappears" when burned, as only the ash is left. Further scientific research has found thatconservation of massholds 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 weight if the mass of combustion gases (such ascarbon dioxideandwater vapor) are not taken into account. The original mass of flammable material and the mass of the oxygen consumed (typically from the surrounding air) equals the mass of the flame products (ash, water, carbon dioxide, and other gases). Lavoisier used the experimental fact that some metals gained mass when they burned to support his ideas (because those chemical reactions capture oxygen atoms into solid compounds rather than gaseous water).
Definitions
[edit]Historically,flammable,inflammableandcombustiblemeantcapable of burning.[1]The word "inflammable" came through French from the Latininflammāre= "to set fire to", where the Latin preposition "in-"[2]means "in" as in "indoctrinate", rather than "not" as in "invisible" and "ineligible".
The word "inflammable" may be erroneously thought to mean "non-flammable".[3]The erroneous usage of the word "inflammable" is a significantsafety 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.[4][5]Antonyms of "flammable" or "inflammable" include:non-flammable,non-inflammable,incombustible,non-combustible,not flammable,andfireproof.
Flammableapplies tocombustiblematerials that ignite easily and thus are more dangerous and more highly regulated. Less easily ignited less-vigorously burning materials arecombustible.For example, in the United Statesflammable liquids,by definition, have aflash pointbelow 100 °F (38 °C)—where combustible liquids have a flash point above 100 °F (38 °C).Flammable solidsare solids that are readily combustible, or may cause or contribute to fire through friction. Readily combustible solids arepowdered,granular, or pasty substances that easily ignite by brief contact with an ignition source, such as a burning match, and spread flame rapidly.[6]The technical definitions vary between countries so theUnited Nationscreated theGlobally 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).[6]
Flammability
[edit]Flammabilityis the ease with which a combustible substance can be ignited, causingfireorcombustionor even an explosion. The degree of difficulty required to cause the combustion of a substance is quantified throughfire testing.Internationally, a variety of test protocols exist to quantify flammability. The ratings achieved are used inbuilding codes,insurancerequirements,fire codesand 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 anoccupancyby altering the flammability of the contents requires the owner of abuildingto apply for a building permit to make sure that the overallfire protectiondesign basis of the facility can take the change into account.
Classification of flammability
[edit]The US Government uses theHazardous Materials Identification System(HMIS) standard for flammability ratings, as do many US regulatory agencies, and also the USNational Fire Protection Association(NFPA).
The ratings are as follows:
Rating | Degree of flammability | Examples |
---|---|---|
0 | Materials that do not burn | water |
1 | Materials that must be preheated before they ignite | lubricating oils,cooking oils |
2 | Materials that must be moderately heated or exposed to relatively high ambient temperatures before they ignite | diesel fuel |
3 | Liquids and solids that can ignite under almost all temperature conditions | gasoline,acetone |
4 | Materials that rapidly vaporize at atmospheric pressure and normal temperatures, or readily disperse in air and burn readily | natural gas,propane,butane |
Examples of flammable substances
[edit]Flammable substances include, but are not limited to:
- Gasoline-Petrol/ a complicated mixture of hydrocarbons that includes isomers ofoctane,C8H18
- Ethanol/ CH3CH2OH
- Rubber
- Isopropyl alcohol/ CH3CH(OH)CH3
- Methanol/ CH3OH
- Wood
- Acetone/ CH3COCH3
- Paper
- Nitromethane/ CH3NO2
Examples of nonflammable substances
[edit]Furniture flammability
[edit]Flammability of furniture is of concern as cigarettes and candle accidents can trigger domestic fires. In 1975, California began implementingTechnical Bulletin 117(TB 117), which required that materials such aspolyurethanefoam used to fill furniture be able to withstand a small open flame, equivalent to a candle, for at least 12 seconds.[7]In polyurethane foam, furniture manufacturers typically meet TB 117 with additive halogenated organicflame retardants.No other U.S. states had similar standards, but because California has such a large market,manufacturersmeet 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. seeDavid Heimbach) for the use of flame retardants, California modified TB 117 to require that fabric covering upholstered furniture meet a smolder test replacing the openflame test.[8]Gov.Jerry Brownsigned the modified TB117-2013, which became effective in 2014.[9]
Fabric flammability
[edit]Lightweight textiles with porous surfaces are the most flammable fabrics.[10]Wool is less flammable than cotton, linen, silk, or viscose (rayon).[10][11]Polyester and nylon resist ignition, and melt rather than catch fire.[10][11]Acrylicis the most flammable synthetic fiber.[10]
Testing
[edit]Afire testcan be conducted to determine the degree of flammability. Test standards used to make this determination but are not limited to the following:
- Underwriters LaboratoriesUL 94 Flammability Testing
- International Electrotechnical CommissionIEC 60707, 60695-11-10 and 60695-11-20
- International Organization for StandardizationISO 9772 and 9773.
- National Fire Protection AssociationNFPA 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
Combustibility
[edit]Combustibilityis a measure of how easily a substance bursts into flame, throughfireorcombustion.This is an important property to consider when a substance is used forconstructionor is being stored. It is also important in processes that produce combustible substances as aby-product.Special precautions are usually required for substances that are easily combustible. These measures may include installation offire sprinklersor 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 resistantsubstances are preferred for building materials and furnishings.
Non-combustible material
[edit]A non-combustible material[12]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.[13]
Combustible dust
[edit]A number of industrial processes producecombustible dustas a by-product. The most common beingwood dust.Combustible dust has been defined as:a solid material composed of distinct particles or pieces, regardless of size, shape, or chemical composition, which presents a fire or deflagrationhazardwhensuspended in airor some other oxidizing medium over a range of concentrations.[14]In addition to wood, combustible dusts includemetals,especially magnesium, titanium and aluminum, as well as othercarbon-based dusts.[14]There are at least 140 known substances that produce combustible dust.[15]: 38 [16]While the particles in a combustible dusts may be of any size, normally they have a diameter of less than 420μm.[14][note 1]As of 2012[update],theUnited States Occupational Safety and Health Administrationhas yet to adopt a comprehensive set of rules on combustible dust.[17]
When suspended in air (or any oxidizing environment), the fine particles of combustible dust present a potential for explosions.Accumulated dust,even when not suspended in air, remains a fire hazard. The National Fire Protection Association (U.S.) specifically addresses the prevention of fires and dust explosions in agricultural and food products facilities in NFPA Code section 61,[18]and other industries in NFPA Code sections 651–664.[note 2]Collectorsdesigned to reduce airborne dust account for more than 40 percent of all dust explosions.[19]Other important processes aregrindingandpulverizing,transporting powders, filing silos and containers (which produces powder), and the mi xing and blending of powders.[20]
Investigation of 200 dust explosions and fires, between 1980 and 2005, indicatedapproximately 100 fatalities and 600 injuries.[15]: 105–106 In January 2003, a polyethylene powder explosion and fire at the West Pharmaceutical Services plant inKinston, North Carolinaresulted in the deaths of six workers and injuries to 38 others.[15]: 104 In February 2008 anexplosion of sugar dustrocked theImperial Sugar Company'splant atPort Wentworth, Georgia,[21]resulting in thirteen deaths.[22]
Important characteristics
[edit]Flash point
[edit]A material'sflash pointis a metric of how easy it is to ignite the vapor of the material as it evaporates into theatmosphere.It is defined as the lowest material temperature required for fuel oils in the materials to begin to give off flammable vapors in the quantity high enough to support a flash of fire when ignited by an external source.[23]A lower flash point indicates higher flammability. Materials with flash points below 100°F(38°C) are regulated in theUnited StatesbyOSHAas potential workplacehazards.
Flame point
[edit]Theflame pointof a material is a temperature value at which sustained flame can be supported on the material once ignited by an external source.[23]Once the flame point of a material is reached, it produces enough fuel vapors or oils to support continuous burning.
Flammability or explosive range
[edit]Thelower flammability limitorlower 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 particular chemical.[24]Any concentration lower than this could not produce a flame or result in combustion. Theupper flammability limitorupper explosive limit(UFL/UEL) represents the highest air to fuel vapor concentration at which combustion can take place when ignited by an external source.[24]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, give an external ignition source, combustion of the particular fuel would likely happen.
Vapor pressure
[edit]Thevapor pressureof 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.[25]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
[edit]TheInternational Code Council(ICC) developed fire code requirements to provide adequate protection to the building and occupants.[26]These codes specify the combustibility rating for materials, the entrance and exit requirements, as well as active fire protection requirements, along with numerous other things. In the U.S. other agencies have also developed building codes that specify combustibility ratings such as state and/or county governing bodies. Following the requirements of these fire codes are crucial for higher occupancy buildings.
For existing buildings, fire codes focus on maintaining theoccupanciesas originally intended. In other words, if a portion of a building were designed as anapartment,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 theactive fire protectionas well as thepassive fire protectionmeans 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.
Code definitions
[edit]For anAuthority Having Jurisdiction,combustibility is defined by the local code. In theNational Building Code of Canada,it is defined as follows:
- Combustible: A material that fails to meet acceptance criteria ofCAN/ULC-S114, Standard Method of Test for Determination of Non-combustibility in Building Materials.
- Non-combustible: means that a material meets the acceptance criteria ofCAN4-S114, "Standard Method of Test for Determination of Non-Combustibility in Building Materials".
BS476-4:1970 defines a test for combustibility in which atechnicianheats three specimens of a material in a furnace. Combustibile materials are those for which any of the three specimens either:
- Makes the temperature reading from either of two thermocouples rise by 50 degrees Celsius or more above the initial furnace temperature
- Flame continuously for 10 seconds or more inside the furnace
Otherwise, the material is classified as non-combustible.
Fire testing
[edit]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 certain amount of mass. As a general rule of thumb, concrete, steel, and ceramics - in other words inorganic substances - pass these tests, so building codes list them as suitable and sometimes even mandate their use in certain applications. InCanada,for instance,firewallsmust be made ofconcrete.
Categorization of building materials
[edit]-
DIN4102 A1 noncombustible rockwool
-
DIN 4102 B1 (difficult to ignite/often self-extinguishing)Siliconecaulking used as a component infirestoppingpipingpenetration
-
DIN 4102 B2: Timber, normal combustibility
-
DIN 4102 B3: Polyurethane foam (easy to ignite = manyhydrocarbonbonds usually)
Materials can be tested for the degree of flammability and combustibility in accordance with the GermanDIN4102. DIN 4102, as well as its British cousinBS476 include for testing ofpassive fire protectionsystems,as well as some of its constituent materials.
The following are the categories in order of degree of combustibility and flammability:
Rating | Degree of flammability | Examples |
---|---|---|
A1 | 100% noncombustible (nicht brennbar) | |
A2 | ≈98% noncombustible (nicht brennbar) | |
B1 | Difficult to ignite (schwer entflammbar) | intumescentsand some high endsilicones |
B2 | Normal combustibility | wood |
B3 | Easily ignited (leicht entflammbar) | polystyrene |
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
[edit]- Explosive material
- Fire
- Fire test
- Fire protection
- Active fire protection
- Passive fire protection
- Flammable liquids
- Flammable limit
- Power tool
- Surface area to volume ratio
- Ultrafine particle
- Underwriters Laboratories
Notes
[edit]References
[edit]- ^inflammable, a. (n.) 1. combustible a. and n. 1.Oxford English Dictionary.2nd ed. 2009. CD-rom.
- ^"flammable",The American Heritage Dictionary of the English Language,5th ed. Houghton Mifflin Harcourt Publishing Company. 2014. accessed 3/11/2015
- ^Sherk, Bill. "fireproof",500 Years of New Words.Toronto: Dundurn, 2004. 96. Print.
- ^Garner, Bryan A.,Garner's Modern American Usage.3rd ed. New York: Oxford UP, 2009. 357. Print.
- ^"inflammable".Common Errors in English Usage, The Web Site of Professor Paul Brians.Washington State University.Retrieved30 June2012.
- ^ab"A Guide toThe Globally Harmonized System of Classification and Labeling of Chemicals(GHS) ".Occupational Safety & Health Administration.U.S. Department of Labor. 2006. Archived fromthe originalon 2007-07-02.Retrieved2015-03-12.
- ^California Department of Consumer Affairs, Bureau of Home Furnishings (March 2000)."Technical Bulletin 117: Requirements, test procedure and apparatus for testing the flame retardance of resilient filling"(PDF)(Report). pp. 1–8. Archived fromthe original(PDF)on 2014-06-11.Retrieved2014-11-04.
- ^"Proposed Regulations - Notice of Proposed New Flammability Standards for Upholstered Furniture/Articles Exempt from Flammability Standards".Department of Consumer Affairs, Bureau of Electronic and Appliance Repair, Home Furnishings and Thermal Insulation. Archived fromthe originalon 2013-05-24.Retrieved2014-11-04.
- ^"Calif. law change sparks debate over use of flame retardants in furniture".PBS Newshour. January 1, 2014.Archivedfrom the original on Nov 2, 2014.RetrievedNovember 1,2014.
- ^abcd"These clothes are the most flammable".Sikker hverdag.Retrieved2023-06-20.
- ^ab"Flammable Fabrics".City of Phoenix.Retrieved2023-06-20.
- ^"NCDOI OSFM Evaluation Services: Subject of White Paper: Classification of Building Materials According to Combustibility"(PDF).NC DOI.8 September 2011. Archived fromthe original(PDF)on Dec 6, 2018.Retrieved6 December2018.
- ^"Standard Test Method for Assessing Combustibility of Materials Using a Vertical Tube Furnace at 750°C".ASTM International.Oct 10, 2022.Retrieved2023-04-10.
- ^abc"Hazard Communication Guidance for Combustible Dusts".Occupational Safety and Health Administration.Retrieved2023-04-10.
- ^abcInvestigation Report No. 2006-H-1, Combustible Dust Hazard Study(PDF),Washington, D.C.: U.S. Chemical Safety and Hazard Investigation Board, 17 November 2006,OCLC246682805,archived fromthe original(PDF)on 21 December 2016,retrieved21 August2017
- ^National Materials Advisory Board, Panel on Classification of Combustible Dusts of the Committee on Evaluation of Industrial Hazards (1980)Classification of combustible dusts in accordance with the national electrical codePublication NMAB 353-3, National Research Council (U.S.), Washington, D.C.,OCLC8391202
- ^Smith, Sandy (7 February 2012)"Only OSHA Has Not Adopted Chemical Safety Board Recommendations Stemming from Imperial Sugar Explosion"EHS Today
- ^"NFPA 61 Standard for the Prevention of Fires and Dust Explosions in Agricultural and Food Processing Facilities"
- ^Zalosh, Robertet al.(April 2005)"Dust Explosion Scenarios and Case Histories in the CCPS Guidelines for Safe Handling of Powders and Bulk Solids"39th AIChE Loss Prevention Symposium Session on Dust ExplosionsAtlanta, Georgia
- ^O'Brien, Michael (2008)"Controlling Static Hazards is Key to Preventing Combustible Cloud Explosions" Newton Gale, Inc.Archived2012-05-07 at theWayback Machine
- ^The chief executive, John C. Sheptor, said the probable cause of the explosion was sugar dust building up in storage areas, which could have been ignited by static electricity or a spark.Dewan, Shaila (9 February 2008)."Lives and a Georgia Community's Anchor Are Lost".The New York Times.Retrieved7 May2012.
- ^Chapman, Dan (13 April 2008)."Sugar refinery near Savannah determined to rebuild".The Atlanta Journal-Constitution.Archived fromthe originalon June 29, 2011.Retrieved7 May2012.
- ^abThangarasu, Vinoth; Anand, R. (2019-01-01), Azad, Kalam (ed.),"11 - Physicochemical fuel properties and tribological behavior of aegle marmelos correa biodiesel",Advances in Eco-Fuels for a Sustainable Environment,Woodhead Publishing Series in Energy, Woodhead Publishing, pp. 309–336,ISBN978-0-08-102728-8,retrieved2023-04-10
- ^abManha, William D. (2009-01-01), Musgrave, Gary Eugene; Larsen, Axel (Skip) M.; Sgobba, Tommaso (eds.),"Chapter 20 - Propellant Systems Safety",Safety Design for Space Systems,Burlington: Butterworth-Heinemann, pp. 661–694,ISBN978-0-7506-8580-1,retrieved2023-04-10
- ^"Vapor Pressure".ch302.cm.utexas.edu.Retrieved2023-04-10.
- ^"Digital Codes".codes.iccsafe.org.Retrieved2023-04-10.
External links
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- 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