Occupational Health

Similarly, a mixture will not be categorized as a flammable liquid if it is composed of at least 99% of components with flashpoints above 100ºF (38ºC). Many mixtures will contain more than 1% of a flammable liquid and the mixture will have a flashpoint above 100ºF.

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Many of these are elements (e.g. , lithium, powdered aluminum, magnesium) or organometallic compounds . Moisture in the air often increases the probability of spontaneous ignition of pyrophoric materials. A mixture will not be categorized as a combustible liquid so long as less than 1% of the total volume of components have flashpoints between 100º and 200ºF. For example, if Chemical A has a flashpoint of 180ºF and represents 0.5% of the mixture and all other chemicals have flashpoints above 200ºF, then the mixture is not considered a combustible liquid.

However, the characterization of the severity of the hazard is usually based upon fairly extensive laboratory testing. Examples of organic peroxides are benzoyl peroxide and allyl hydroperoxide.

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  • Following is a brief description of the HCS identified health hazards.
  • Agents having an oral LD50 greater than 500 mg/kg are not classified as toxic.
  • This does not mean that they do not represent a health hazard (e.g. , the chemical could present a chronic hazard, such as cancer or hepatotoxicity), but only that they are not classified as toxic under the HCS.
  • Examples of toxic chemicals are chloroform (with an LD50 of 140 mg/kg), acrylonitrile (with a 24-hour dermal LD50 between 200 anxiety disorder and 2000 mg/kg), and ammonia (with an inhalation one-hour LC50 in rats between 200 ppm and 2000 ppm).

Where data indicating the flashpoint of a chemical are not available, you may choose to test the chemical to determine the flashpoint. The ability of a chemical to either burn or support burning is a potentially disastrous physical hazard. The two primary measures of the ease with which a liquid will burn are the flashpoint and autoignition temperature. The flashpoint is the lowest temperature at which a liquid will emit sufficient vapors to form an ignitable mixture with air. In contrast, autoignition is the characteristic of a material in which it will spontaneously burn without the aid of an ignition source, such as a spark or flame.

Many agents will burn when ignited whereas there are only a few that will spontaneously erupt into flames. While no single measure of flammability is sufficient for all purposes, the most commonly found measure in the literature is the flashpoint. For this reason, HCS uses flashpoint in classifying the fire hazard of a chemical. In the remainder of this section, an overview is presented of the HCS designated hazards and their definitions. In addition, a brief discussion is presented to further explain the specific hazard as well as procedures that can be used to analyze the data.

While there are classes of chemicals that in themselves may be reactive, there are also stable chemicals which are not reactive but when combined may interact, resulting in an explosive reaction. Good sources for information about chemical interactions are Bretherick , Sax , and the U.S. Mixing incompatible materials may result in the formation of unstable/reactive materials; therefore, the literature search should document incompatible materials. In addition to discrete chemicals, it should be realized that certain dusts might be combustible and explosive, such as that produced by bakeries, sawmills, and in grain handling.

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