The events at the Fukushima Dai-ichi nuclear power plant in March 2011 clearly showed the importance of the problem related to the possibility of generating and spreading gaseous hydrogen in the containment building. Equally clearly, the problems arising from the total loss of electricity supply of the nuclear power unit could also be observed. A commonly observed trend associated with the above-mentioned problems is the use of Passive Autocatalytic Recombiners (PAR) to remove hydrogen from the nuclear reactor containment. This type of device does not require external energy supply, and the reduction of the amount of hydrogen occurs as a result of its controlled oxidation on the surfaces of PAR devices' cartridges covered with a catalytic layer. In the case of water nuclear reactors, particularly intense hydrogen generation may occur in the event of insufficient cooling of the reactor core. Limiting the cooling capacity may be the result of e.g. stopping the forced circulation of the coolant or its leakage from the primary circuit. The removal of this gas in PAR devices takes place in an exothermic oxidation reaction. Analysis of the impact of the operation of the hydrogen removal system in the form of PAR by using an in-house code based on a lumped parameter model has been carried out. Main results are time trends of thermodynamic parameters (temperature, pressure) inside compartments of the pressurized water reactor containment. The analysis was carried out for the cases of hydrogen release into the containment as a result of pressure relief valves activation, as well as as a result of a loss-of-coolant accident. The thermodynamic effects of passive hydrogen recombination seem to be more significant in the first of the considered scenarios. However, a reliable assessment of the impact of such a system on the course of changes in thermodynamic parameters also requires consideration of other factors that have been identified in the work.