Volatile liquid spills

Source models describe tlie release rate of material from tlie process equipment into tlie external enviromiient, and tlie rate of release of spilled vapors and volatile liquids into the atmosphere. 

Where complete containment is impractical, exhaust ventilation (preferably to a scrubber) can limit or eliminate exposure to toxic materials. The exhaust ventilation rate (velocity or volumetric rate) may be calculable for volatile liquids from spill size and vapor pressure (U.S. Environmental Protection Agency, Risk Management Program Guidance for Offsite Consequence Analysis, Appendix D, Equation D-l, 1999), but tests to determine concentrations in air usually would be needed for dusty processes and fugitive releases of gases. 

Clear, colorless to pale yellow-brown, watery, volatile liquid with a sweet, irritating or pungent odor resembling peach pits, onions, or garlic. Evaporates quickly when spilled. Turns dark on exposure to air. Odor threshold concentrations of 1.6 and 8.8 ppmv were reported by Stalker (1973) and Nagata and Takeuchi (1990), respectively. 

The primary parameters affecting entrainment and evaporation are solar radiation, ambient temperature, storage or process temperature and pressure, liquid spill surface area, wind speed and the properties of the spilled material (such as vapor pressure, surface tension, and viscosity). Suppressing volatility by reducing containment temperature and constraining pool size or exposed surface area via a dike or berm are effective postmitigation approaches and are discussed in Chapters 3 and 5. 

McDonald TJ, Brooks JM, and Kennicut MC. 1984. Release of volatile liquid hydrocarbons from spilled petroleum. Bull Contam Toxicol 32(5) 621-628. 

Another term associated with vapor is volatility. It is the tendency of a solid or a liquid to pass into the vapor state easily. This usually occurs with liquids that have low boiling points. A volatile liquid or solid will produce significant amounts of vapor at normal temperatures, creating an additional flammability hazard. The vapor produced by a volatile liquid is affected by wind, vapor pressure, temperature, and surface area. Temperature always causes an increase in vapor pressure and vapor content in an incident. The more vapor pressure in a container, the greater the chance of container failure. The more vapor content, the farther the vapor may travel away from a spill. 

A collecting sump can be designed with a small area exposed to the atmosphere. This reduces the rate of mass transfer (i.e., the rate of formation of vapor). It also provides an opportunity to apply a cover and vent the sump to an absorption device. Figure 16.4 shows some of the design practices that contribute to mitigation of the results of a spill of a volatile liquid. 

Exhibit 15-11 shows how natural terrain is used to direa spills from spheres of highly volatile liquid to flow to a. single sump. This is done by installing a diversion dike between the spheres to reduce the risk... 

Solvent spills. Untrained workers fi-equently attempt to clean up spills involving volatile liquids by using absorbent material, such as paper towels, or by mixing the spilled liquid with an inert solid like diatomaceous earth or sand. These methods do not control the vapors produced by the spilled liquid. Thus, the hazard of the spill becomes portable because the toxic, flammable, or explosive vapors fi om the liquid will continue to be generated wherever the wastes are carried to or disposed of. Use spill control methods designed for control of vapors, discussed below. 

Equation 3-12 is used to estimate the vaporization rate of volatile from an open vessel or from a spill of liquid. 

A. Compound Volatility. One is sometimes required or requested to evaluate the potential irritancy of a liquid that has a boiling point between room temperature and the body temperature of the test animal. As a result, the liquid portion of the material will evaporate off before the end of the testing period. There is no real way around the problem one can only make clear in the report on the test that the traditional test requirements were not met, though an evaluation of potential irritant hazard was probably achieved (for the liquid phase would also have evaporated from a human that it was spilled on). 

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