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Don't get burned - Know the limits of flammable and combustible fluids

Schmidt, M.

The words 'flammable' and 'combustible' have very specific meaning within the context of fire prevention and suppression. The Flammable and Combustible Liquids Code of the National Fire Protection Assn. (NFPA; Washington, D.C.; nfpa.org) makes the distinction between a flammable and a combustible liquids based on the liquid's boiling point and flashpoint. The division between flammable and combustible is at a flashpoint of 100 deg F. That temperature represents the upper limit of ambient temperatures one might expect to encounter in all but the hottest climates. Liquids with a flashpoint below 100 deg F are flammable; they are called Class I flammable liquids. Liquids with a flashpoint above 100 deg F are combustible. Liquids with a flashpoint between 100 deg F and 140 deg F are Class II combustible liquids. Liquids with flashpoints above 140 deg F are defined as a Class III combustible liquids. Class I flammable liquids are further divided into three sub-classifications. Class I flammable liquids with flashpoints between 73 deg F (room temperature) and 100 deg F are Class IC flammable liquids. If the flashpoint of a liquid is less than room temperature, then the NFPA looks at boiling point. If its flashpoint is less than room temperature and its boiling point is higher than 100 deg F, then liquid is defined as a Class IB flammable liquid. If its flashpoint is less than room temperature and its boiling point is less than 100 deg F then a liquid is defined as a Class IA flammable liquid - the most dangerous of all the flammable and combustible liquids. Storage, handling. and use of these chemicals require the greatest restrictions. Class II combustible liquids is not sub-divided. Class III combustible liquids are divided into two sub-classifications (Class IIIA with flashpoints between 140 deg F and 200 deg F, and Class IIIB with flashpoints above 200 deg F). To the paper is adapted a table 'Ignitability Properties of an Assortment of Liquids' as well as a table 'Aqueous Mixtures of Flammable Liquids'.