Now detectors that sensing on two and more fire physical factors have appeared and get popular application. These detectors are different concerning usual combined fire detectors and they use more difficult algorithm of information processing. The considered classification of multicriterial fire detectors has allowed to dedicate two features accounting various ways of their technical implementation. The first feature is probably number of used types of monitored physical environment parameters. Now four main channels of detection are actively used in such detectors: heat, smoke, flame and gas. However, this list doesn’t limit possible detected factors of ignition. Now there are known, for example, devices which use acoustic effects, conducting fire, change video image within scene of specter and others. The second feature is way of technical implementation of detection channel. They can be joined by one constructively completed unit or be multiblock structure, with wire communication lines between cooperated components and with fire control panel. Construction complication and the introduction additional connections negatively influence on detector’s reliability. Thus, during evaluating of efficiency it is necessary additionally to consider important indicator - reliability, which can be characterized by degree of readiness of multicriterial fire detector to perform its main function of fire detection at any moment of time. In this article the opportunity of introduction of complex indicator “technical readiness” of multicriterial fire detector is considered. This indicator is probability of performance by multicriterial fire detector the main preset task (objective function), that consists in insured fire detection. The mathematical expression for technical efficiency of multicriterial fire detector is received. Its numeric analysis for determination of dependences character of “technical efficiency” from number of detection channels at different values of detection channels characteristics and parameters their reliability is carried out. The opportunity of construction detector’s optimization by usage of introduced parameter is shown in this article. The offered parameter of technical efficiency may be used in well-founded cases for designing and application of multicriterial fire detector and also for modular complexes and fire alarm systems.