Abstract
Aim: The purpose of this article is to help designers of fire detectors with the selection of a carbon monoxide (CO) sensor for a multi-sensor fire detector. Academic work on detectors provides an abundance of material about sensors suitable for CO analysis. Each sensor has its advantages and disadvantages. Therefore, choosing a suitable sensor is quite difficult. The authors, based on their extensive experience in the development and production of devices for gas analysis and fire detectors, propose most adequate solutions.
Introduction: Current devices for discovering a fire, work on the principle of detecting smoke, often incorporating a temperature sensor. However, these have many disadvantages. They do not function in a discerning way in relation to smoke (aerosols, water vapour, cooking vapour and dust are all identified as smoke). A CO fire detector is free of these shortcomings, since it is selective and reacts to CO. For this reason many perspective European norms and international standards emerged, which recommend CO analysis for detection of fires. Obviously, high concentrations of CO can occur in areas where people smoke, where heating appliances utilising solid and gaseous fuels are used, in garages and in underground car parks. Multi-Sensor Detectors with two methods of detecting fire, CO and smoke, compensate shortcomings of each method. It can be confidently stated that through a simultaneous response from both detection methods, a fire will be dealt with at an early stage of development and resources will not be sidetracked by dust, water vapour, aerosols or high concentration of CO. For detection of CO, existing standards recommend the use of electrochemical sensors.
Methodology: The article describes the technical parameters of the most appropriate electrochemical sensors for monitoring of CO. These are electrolytic, based on acidic electrolyte and metal oxide semiconductors, namely Nap-508 (505) and TGS2442. The principles of operation and recommended circuit connection are suitably described in the article. The sensors are specially designed for use with gas fire detectors and were tested in accordance with requirements for fire detectors. It is noted that metal-oxide sensors have the most acceptable performance characteristics, across the broadest temperature range, long period of validity and absence of aggressive substances in composite elements. Among its disadvantages is a relatively high power consumption ~ 15 mW.
Conclusions: Examined prospects for the development and production of metal oxide semiconductor sensors. It is indicated that the use of micro and nanotechnology in the manufacture of sensors will solve the problem of reducing energy consumption to a level sufficient for the production of self-contained smoke detectors powered by batteries. At present, Figaro has developed a sensor TGS8410 with an average power consumption of 0.087 mW.
Keywords: fire, detector, multisensory, gas, sensor, concentration, electrochemical, electrolytic, oxidic
Type of article: review article