Direct calorimetry is used for investigating combustion energy of fuels, thermic properties of materials and metabolic processes. Its results, however, may be influenced by the dynamic properties of the equipment, if they are not much faster than those of the subject. When performing direct calorimetry at living beings, the dynamic properties of the system chamber-interior-subject must be taken into account. A simple model is known to correct for the dilution of metabolic gases in the chamber. Heat, however, is not simply diluted; it is stored in the chamber’s interior and the subject’s body too. A two-compartment-model was shown to correct heat storage effects in a furnished human calorimetric chamber. A method was established to estimate proper model parameter from alcohol combustion as calibration experiments. Heat storage resulted in 7.8 +/- 1.1% of all heat measured after extinguishing the flame. The ’wake period’ lasted more than 3 h. Using the two-compartment-model this was overcorrected to -1.6 + 1.9% with the ’wake period’ being less than 15 min. Humans or animals in the chamber would change the model parameter dramatically due to their large heat capacity. The corresponding parameters could not be derived from only a few calibration experiments; more work needs to be done in the future.