A reaction chamber was developed to determine the respiratory activity of microorganisms immobilized on various support materials for waste gas treatment. The volumetric respiration rate was identified as a suitable parameter for estimating the degradative activity of waste gas treatment plants. A laboratory trickle-bed reactor was filled with either granular clay, polyamide beads, or sintered styrofoam. n-Butanol was used as model solvent to determine the efficiency of its elimination from the gas phase. This crucial parameter was correlated with the volumetric degradation rate, determined from the overall material balance under steady-state operating conditions. The volumetric respiration rate of n-butanol was determined with the reaction chamber, and exceeded the volumetric degradation rate of n-butanol determined from the reactor 16- to 26-fold, depending on the support material. The respiration rate was correlated to the degradation rate by the stoichiometry of n-butanol oxidation and a correlation factor of 2.6-4.3. The volumetric respiration rate appeared to be a suitable parameter to determine the degradative activity of the trickle-bed reactor used. The volumetric respiration rate can be ultimately applied to estimate the efficiency of elimination of an organic pollutant and to calculate the dimensions of a reactor required to eliminate a given organic load from waste gas.