This part of ISO 7240 specifies requirements, test methods and performance criteria for point-type resettable multisensor fire detectors for use in fire detection systems installed in buildings, incorporating in one mechanical enclosure at least one smoke sensor and at least one other sensor which responds to heat, and inwhich the signal(s) of the smoke sensor(s) is (are) combined with the signal(s) of the heat sensor(s).The performance of single components within a multisensor fire detector covered by this standard may not be sufficient for conformity to other standards for the single sensor. Certain types of detectors may contain radioactive materials. The national requirements for radiationprotection differ from country to country and they are not therefore specified in this standard. However, such detectors are expected to conform to the national requirements and be in line with the recommendations of the Nuclear Energy Agency (NEA) of the Organisation for Economic Co-operation and Development (OECD)1) .