User:JeffreySalisbury/Combustibility and flammability

Combustibility[edit]

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.

Combustible dust[edit]

Main article: Dust explosion

A number of industrial processes produce combustible dust as a by-product. The most common being wood 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 deflagration hazard when suspended in air or some other oxidizing medium over a range of concentrations. In addition to wood, combustible dusts include metals, especially magnesium, titanium and aluminum, as well as other carbon-based dusts. There are at least 140 known substances that produce combustible dust. While the particles in a combustible dusts may be of any size, normally they have a diameter of less than 420 μm. As of 2012, the United States Occupational Safety and Health Administration has yet to adopt a comprehensive set of rules on combustible dust.

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, and other industries in NFPA Code sections 651–664. Collectors designed to reduce airborne dust account for more than 40 percent of all dust explosions. Other important processes are grinding and pulverizing, transporting powders, filing silos and containers (which produces powder), and the mixing and blending of powders.

Investigation of 200 dust explosions and fires, between 1980 to 2005, indicated approximately 100 fatalities and 600 injuries. In January 2003, a polyethylene powder explosion and fire at the West Pharmaceutical Services plant in Kinston, North Carolina resulted in the deaths of six workers and injuries to 38 others. In February 2008 an explosion of sugar dust rocked the Imperial Sugar Company's plant at Port Wentworth, Georgia, resulting in thirteen deaths.

Important characteristics[edit]

Flash point[edit]

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. It is defined as the lowest surface temperature required for fuel oils in the materials to being to give off flammable vapors in the quantity high enough to support a flash of fire when ignited by an external source. 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.

Flame Point

The flame point of a material is a value at which sustained flame can be supported on the material. The flame point is usually close to the flash point (within a few degrees Fahrenheit) and signifies the point at which the ma

Vapor pressure[edit]

• 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.

Codes[edit]

The International Code Council (ICC) developed fire code requirements to provide adequate protection to the building and occupants. 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.

Flammability[edit]

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.

Code definitions[edit]

For an Authority Having Jurisdiction, combustibility is defined by the local code. In the National Building Code of Canada, it is defined as follows:

• Combustible: A material that fails to meet acceptance criteria of CAN/ULC-S114, Standard Method of Test for Determination of Noncombustibility in Building Materials.

This leads to the definition of noncombustible:

• Non-combustible: means that a material meets the acceptance criteria of CAN4-S114, "Standard Method of Test for Determination of Non-Combustibility in Building Materials".

BS 476-4:1970 defines a test for combustibility in which a technician heats 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]

Main article: Fire test

Various countries have tests for determining noncombustibility 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. In Canada, for instance, firewalls must be made of concrete.

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