Among all the confinement equipments found in nuclear plants, several have been the subject of research works at the "Institut de Protection et de Sûreté Nucléaire" (IPSN) in order to characterize their behaviour when they are submitted to stresses (temperature, clogging by combustion aerosols, presence of incandescent particles) resulting from fire. HEPA (High Efficiency Particulate Air) filters require special attention because they are the last confinement barrier of radioactive substances before they are released into the environment. The proposed paper presents the results specific to the behaviour of HEPA filters in terms of clogging by combustion aerosols and mechanical strength related to effects coupled with temperature and clogging. First, it highlights the need to use experiments for access to realistic data about industrial filter clogging because the theoretical models currently available appear to be limited; fires of solvents used in reprocessing facilities illustrate the influence of the filtration velocity upon the clogging curves. The communication gives subsequently the pressure drop from which an HEPA filter loses efficiency for a given temperature; several types of filters used in French nuclear facilities have been tested.