Some Chemicals Requiring Special Consideration when Deciding Whether to Sample the Particle, Vapor, or Both Phases of an Atmosphere

Publisher Website
Google Scholar
Abstract
When preparing to measure the concentration of a contaminant in air, a decision must be made whether to sample the particle phase, the vapor phase, or both. The choice to sample only the particle phase or only the vapor phase seems obvious for many contaminants due to their extremely high or low vapor pressures. This work identifies some chemicals that are likely to occur in both the vapor and particle phases in some atmospheres and identifies others for which readily available information may be inadequate or misleading. The saturated vapor concentration (SVC) of numerous chemical substances was calculated from vapor pressure information given in the Documentation of the Threshold Limit Values and Biological Exposure Indices published by the American Conference of Governmental Industrial Hygienists (ACGIH). The results were used to calculate the ratio of SVC to the threshold limit value (TLV) for each substance. Forty-one substances that had a TLV listed only in mg/m3 were found to have a SVC greater than their TLV. In situations where a material's SVC is greater than its total air concentration, a significant fraction can be expected to exist in the vapor phase. Forty-six substances were identified that had TLVs listed in both ppm and mg/m3 and had SVCs which were one to one hundred times higher than their TLVs. These substances would normally be expected to be present in the vapor phase. In atmospheres where the vapor of any of these substances coexists with particles that may adsorb or solubilize the vapor, a significant fraction of these materials may exist in the particle phase. These 87 substances are examples of chemicals whose airborne concentrations might be underestimated if an industrial hygienist samples only the vapor phase or only the particle phase of an atmosphere. A listing of additional substances whose SVC could not be determined with the information available in the TLV documentation is also included. It is recommended that ACGIH include additional information about saturated vapor concentrations and their importance in the TLV publications.

This publication has 2 references indexed in Scilit: