DEVELOPMENT OF A MODEL TO PREDICT AIR CONTAMINANT CONCENTRATIONS FOLLOWING INDOOR SPILLS OF VOLATILE LIQUIDS

A personal computer spreadsheet model which predicts air contaminant c oncentrations following indoor spills of volatile liquids has been dev eloped. Three mass transfer models are compared for predicting evapora tive flux in the model, the flat plate mass transfer theory, Penetrati on Theory, and Mackay and Matsugu models. Two methods of predicting sp ill temperature during evaporation are presented, the isothermal metho d, which assumes spill temperature remains at ambient throughout evapo ration, and the spill temperature method, which predicts spill tempera ture using equations developed from a heat balance over the spill pool . Dispersion is approximated in the model as a well-mixed room with sh ort-circuiting. Model equations are programmed into a Lotus 1,2,3 spre adsheet. Calculations of room concentration, spill pool surface temper ature, and spill area are made at consecutive 20-s intervals following the spill. Model predictions are compared with concentration measurem ents made after two test spills in a laboratory. The model gives a goo d first estimate of room concentration, performing best when the spill is assumed to be isothermal and the Penetration Theory or Mackay and Matsugu methods are used to predict evaporation rate. (C) 1997 British Occupational Hygiene Society. Published by Elsevier Science Ltd.