(78s) EVALUATION OF EQUILBRIUM TOXICITY HAZARDS USING “INFINITE POINTS”

For evaluation of the inhalation toxicity hazards to which a worker could be exposed, it is necessary to know (1) the concentration of the gas or vapor in the surrounding atmosphere and (2) the concentration that would be hazardous. Where there is liquid in an unventilated enclosed space, the maximum concentration would be determined from the vapor pressure of the liquid at the temperature within the enclosure. For many chemicals, the relationship between temperature and vapor pressure is not known over a wide range. If the boiling point is known, or if the vapor pressure at a given temperature is known, an approximate relationship between vapor pressure and temperature can be obtained through the use of an ?infinite point?.

This paper presents ?infinite points? for a variety of compounds (as developed by previous investigators) and the equations that can be used to estimate the vapor pressure (and, thereby, the concentration) at any temperature. If the relationship between atmospheric concentration and toxic concentration can thus be evaluated, the required ?protection factor? for respiratory equipment can then be determined. Similarly, if the approximate vapor-pressure/temperature relationship is known for a material, the flash point can be estimated.