Abstract
Aim: There is a need of fire detection solutions which are sensitive to deceptive signals. They can lead to false fire alarms. One of such signals is the activation of detectors in case of wooden dusts accumulated in the protected area which is regarded by the detector as smoke with large particles. This paper describes selected experimental results on various detectors and different wooden dusts. The aim of this project is to select a detector that is highly resistant to dust particles.
Introduction: During designing fire detection systems there is always a problem in a proper selection of fire detectors operating in environments where there are various sources of false alarms. Initially, the influence of cellulose dusts as could be observed during the production of newspapers at the printing house was studied. Then the influence of other dusts was analyzed. During the measurement of smoke particles of different sizes the influence of particles on the detection cannot be explicitly determined. Due to this fact, tested dust was divided taking into consideration the size of the particles where the diameter was 100 μm, 200 μm and 500 μm. It made it possible to test the influence on the operation of the detectors of not only wooden-based materials but also of the size of dust particles.
Methodology: During the tests the methodology of measuring the influence of dust on the activation time of detectors was prepared. The pressure of the compressed air was set at 1,5 bars together with the opening time of the valve of the compressed air container in order for the dust to be emitted evenly in the test chamber. If the valve opening time was too short, the dust remained in the container. If it was too long – the dust was blown all over the chamber. The optimum time was set as 3 s. Tested detectors were located by the ceiling of the chamber in the following manner: transmitter-receiver, transmitter-prismatic mirror on opposite walls. Measurement results were registered using a computer system.
Conclusions: As a result of the conducted tests, which included the behaviour of fire detectors smoke, the best design solution was determined that best coped with duste present in protected areas. It is OSID smoke detection system. It is a result of how the signal was processed by the detector. The size of dust particles and, to a smaller degree, type of dust with respect to the tested species of wood influenced the operation of the smoke detector.
Keywords: fire detection systems, smoke detectors, false alarms, wooden dust
Type of article: original scientific article