“Application of a Pilot Control Banding Tool for Risk Level Assessment and Control of Nanoparticle Exposures” (Paik et al., 2008)

   “‘Stoffenmanager,’ a Web-Based Control Banding Tool Using an Exposure Process Model” (Marquart et al., 2008)

   “History and Evolution of Control Banding: A Review” (Zalk and Nelson, 2008)

   “Control Banding: Issues and Opportunities.” A Report of the ACGIH Exposure Control Banding Task Force (ACGIH, 2008a)

   “Evaluation of the Control Banding Method—Comparison with Measurement-Based Comprehensive Risk Assessment” (Hashimoto et al., 2007)

   Guidance for Conducting Control Banding Analyses (American Industrial Hygiene Association, 2008)

4.D FLAMMABLE, REACTIVE, AND EXPLOSIVE HAZARDS

In addition to the hazards due to the toxic effects of chemicals, hazards due to flammability, explosivity, and reactivity need to be considered in risk assessment. These hazards are described in detail in the following sections. Further information can be found in Bretherick’s Handbook of Reactive Chemical Hazards (Urben, 2007), an extensive compendium that is the basis for lists of incompatible chemicals included in other reference works. The handbook describes computational protocols that consider thermodynamic and kinetic parameters of a system to arrive at quantitative measures such as the reaction hazard index. Reactive hazards arise when the release of energy from a chemical reaction occurs in quantities or at rates too great for the energy to be absorbed by the immediate environment of the reacting system, and material damage results. An additional resource is the Hazardous Chemical Handbook (Carson and Mumford, 2002). The book is geared toward an industrial audience and contains basic descriptions of chemical hazards along with technical guidance.

Box 4.2 is a quick guide for assisting in the assessment of the physical, flammable, explosive, and reactive hazards in the laboratory.

4.D.1 Flammable Hazards

4.D.1.1 Flammable Substances

Flammable substances, those that readily catch fire and burn in air, may be solid, liquid, or gaseous. The most common fire hazard in the laboratory is a flammable liquid or the vapor produced from such a liquid. An additional hazard is that a compound can enflame so rapidly that it produces an explosion. Proper use of substances that cause fire requires knowledge of their tendencies to vaporize, ignite, or burn under the variety of conditions in the laboratory.

For a fire to occur, three conditions must exist simultaneously: an atmosphere containing oxygen, usually air; a fuel, such as a concentration of flammable gas or vapor that is within the flammable limits of the substance; and a source of ignition (see Figure 4.3). Prevention of the coexistence of flammable vapors and an ignition source is the optimal way to deal with the hazard. When the vapors of a flammable liquid cannot always be controlled, strict control of ignition sources is the principal approach to reduce the risk of flammability. The rates at which different liquids produce flammable vapors depend on their vapor pressures, which increase with increasing temperature. The degree of fire hazard of a substance depends also on its ability to form combustible or explosive mixtures with air and on the ease of ignition of these mixtures. Also important are the relative density and solubility of a liquid with respect to water and of a gas with respect to air. These characteristics can be evaluated and compared in terms of the following specific properties.

4.D.1.2 Flammability Characteristics

4.D.1.2.1 Flash Point

The flash point is the lowest temperature at which a liquid has a sufficient vapor pressure to form an ignitable mixture with air near the surface of the liquid. Note that many common organic liquids have a flash point below room temperature: for example, acetone (–18 °C), benzene (–11.1 °C), diethyl ether (–45 °C), and methyl alcohol (11.1 °C). The degree of hazard associated with a flammable liquid also depends on other properties, such as its ignition point and boiling point. Commercially obtained chemicals are clearly labeled as to flammability and flash point. Consider the example of acetone given in section 4.C.1.3.1. At ambient pressure and temperature, an acetone spill produces a concentration as high as 23.7% acetone in air. Although it is not particularly toxic, with a flash point of -18 °C and upper and lower flammable limits of 2.6% and 12.8% acetone in air, respectively (see Table 4.4), clearly an acetone spill produces an extreme fire hazard. Thus the major hazard given for acetone in the LCSS is flammability.

4.D.1.2.2 Ignition Temperature

The ignition temperature (autoignition temperature) of a substance, whether solid, liquid, or gaseous, is the minimum temperature required to initiate or cause self-sustained combustion independent of the heat source. The lower the ignition temperature, the greater the potential for a fire started by typical laboratory



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement