Comparison of Three Air Transport Models for Safety Applications under Diffusive Conditions Using Full-Scale Experimental Data: EPIcode, ALOHA, and SCIPUFF

Abstract

This paper compares three current state-of-the-practice models, ALOHA, EPICode, and SCIPUFF for use in safety evaluations using data from a unique full-scale field experiment under low-wind speed conditions. The experiment included the release and transport of three gases: ammonia (buoyant), ethylene (neutral buoyant), and propylene (dense) in low-wind speed (diffusion) conditions, less than 2 m/s. In total there were 30 releases ranging from 6 to 30 min in duration. The diagnostics included nine meteorology stations on 100-m centers and 36 photo ionization detectors in a radial pattern. Diffusive conditions are difficult to model, and all of the models had difficulty replicating the field measurements. However, the work does show that these models, if used correctly, are conservative (overpredict concentrations) and can be used for safety and emergency planning.