Abstract
Aim: The aim of the study is to demonstrate the possibility of increasing the sensitivity, resistance to electromagnetic interference and response speed of point smoke detectors on the basis of using laser processing and fibre optics technology.
Project and methods: In order to achieve the above goal an optical point smoke detector was designed and produced. The detector uses a laser radiation source and fibre-optic communication line with a radiation receiver.
Results: The combined laser-based fire alarm device which includes two smoke detection methods (controlling the intensity of radiation scattered by smoke particles and passed through the smoke without scattering) and carbon monoxide detector are produced. The tests of the fire detector to determine its basic functional parameters and the performance of detecting the test fire sources in accordance with standard SТB 16.03-2009. The minimum threshold quantity of optical smoke density detected in the control channel of the intensity of scattered radiation is 0.05 dB/m. The minimum threshold quantity of optical smoke density detected in the control channel of the intensity of radiation passing through the smoke without scattering is about 0.9 dB/m for controlled optical length 25 mm. The minimum concentration of carbon monoxide detection by the CO gas detector is 40 ppm. The testing results of combined laser-based fire alarm device on the detection efficiency of the standardised fire source bear record to its hypersensitivity for different types of smoke and a higher speed of detection of fires in comparison with single-channel point smoke detector. The tests of the combined laser fire detector to determine the efficiency of the fire detection model point to its increased sensitivity to different types of smoke and fire detection speed in comparison with a conventional single-channel point smoke detector. Using fibre optics for recording radiation getting through smoke without dissipation showed us the possibility of developing a point smoke detector on the linear principle of smoke detection with signal processing at a distance from the controlled zone in a well-screened box, for instance, inside a fire alarm control panel. Obviously, the signaling device will be highly resistant to electromagnetic interference due to the reliable screening of the sensitive elements of the electronic signal processing system and the lack of wiring connected to the fire alarm control panel.
Conclusions: The advanced functional characteristics of the fire alarm device are provided thanks to the application of a laser source with a high intensity and a low divergence of radiation. The unique properties of laser radiation in the sensor’s structure made it possible to apply a number of design and technical solutions which provided a substantial increase in the sensitivity and fire detection rate of the sensor compared to the currently used traditional LED smoke detectors.
Keywords: dual fire sensor, point smoke detector, linear smoke detector, laser source, optical fibre, sensitivity
Type of article: review article