Spontaneous Heating/Ignition of Organic Materials

SPONTANEOUS HEATING/IGNITION

OF HYDROCARBONS AND ORGANICS

DOE-HDBK-1081-94

Spontaneous Heating and Pyrophoricity

out over a larger surface area, allowing more contact with oxygen. Therefore, porous

combustible materials are more likely to ignite than tightly packed solid materials.

These principles are illustrated in Figure 2. Although coal is used as the example in Figure

2, the principles depicted apply to all materials which are known to heat spontaneously

(including pyrophoric liquids, gases, metals, and other solids).

It is important to keep potentially spontaneously heating compounds as dry as possible. High

ambient temperatures compound moisture problems. As the ambient temperature rises, the

rate of spontaneous heat generation will also rise. High ambient temperatures also reduce the

rate of heat removal, bringing the hydrocarbon closer to its ignition temperature.

With these facts in mind, the following housekeeping steps will help minimize the threat of

spontaneous heating and ignition of hydrocarbon or organic compounds:

Keep potentially spontaneously heating materials in a cool environment. The heat

transfer resulting from a cooler atmosphere or circulating air will lower the

temperature of the materials.

Know all of the chemicals and their potential self-heating hazards and their ignition

temperatures. Consult the chemical manufacturer's MSDSs.

Reduce the amount of fibrous materials used with combustible liquid hydrocarbons.

Fibers allow liquid hydrocarbons to increase in specific areas, thereby increasing the

likelihood of self-heating.

Keep combustible materials away from existing spontaneous heating hazards. Many

fires have been started as the result of a self-heating material coming in contact with a

combustible with a low ignition temperature. This practice is also important from a

fire loss minimization aspect.

Keep appropriate fire extinguishing equipment near potential areas of ignition. Type

A extinguishing agents are appropriate for most nonhazardous, combustible materials

(rags, wood, textiles), whereas a Type B agent is necessary in the presence of

quantities of combustible liquids. Extinguishing agents for metal fires are discussed in

a later section.

Spontaneous Heating/Ignition of Organic Materials

Spontaneous combustion may occur in piles of moist organic material where heat is

generated in the early stages by the respiration of bacteria, molds, and microorganisms. A

high moisture content is required for vigorous activity, and heating is generally controlled by

maintaining the moisture content below a predetermined level. This type of heating can only

Pyrophoricity

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