The fire detector provides reliable early warning of a fire condition, responding to a fixed smoke concentration threshold or rate of temperature rise, or a fixed temperature threshold detected in protected premises. It combines the advantages of a VIT30 type and a VIT20 type and is an attractive option due to lower supply and installation costs. The temperature class (A1R, A2R) and the sensitivity to smoke (low, medium or high) are programmable by the VIT01 fire control panel and comply with the European standard EN54-5 and EN54-7. The principle of operation of its thermal part is based on the alteration of the ohmic resistance in the thermistors as a consequence of the change in ambient temperature. The principle of operation of the optical chamber is based on the dispersion of infrared rays from the smoke particles, trapped in the optical chamber.