Mathematical Model for Determining Rate of Kill of Microbial Aerosols by Vapor-Phase Disinfectants

摘要

A method for screening chemical vapors for decontaminating microbial aerosols was developed by applying Raoult's law. The method included a simple small-scale aerosol chamber system that was conveniently and rapidly operated by one person. The vegetative bacterium Serratia marcescens (SM) was used for the test aerosols. The maximum decay rate of an SM aerosol in a disinfectant vapor at a given relative humidity (RH) was determined by determining the decay rate of an SM aerosol in the equilibrium vapor over a binary solution of disinfectant and water. Ternary solutions of disinfectant, water, and a nonvolatile nonelectrolyte were used to obtain any selected concentration of disinfectant vapor and water vapor. Relationships between the SM aerosol decay rate and the independent variable (equilibrium vapor) were reduced to equations by regression analysis and/or described graphically. It was possible to predict the SM aerosol decay rate over the whole vapor composition range from limited experimental data simply because the relationship between the SM aerosol decay rate and the equilibrium vapor is first order when vapor composition is expressed thermodynamically; i.e., in mole fractions. Vapors tested included formic acid, propionic acid, lactic acid, glycolic acid, levulinic acid, ethylene glycol, propylene glycol, and methyl sulfoxide. The modeling experiment was done with formic acid vapor.