Electrostatic Fire Detection

Experimental work was carried out to determine the feasibility of detecting flames by means of an insulated wire grid placed over the entire surveillance area thus eliminating expensive individual detectors. By maintaining the umbrella grid at an electric potential, charged particles and ions are "extracted" from the flames. As they move toward the grid, they are deposited on the interposing surfaces and their accumulation is detected in the form of an electric current. To eliminate the effect of ambient ions which also act as an electric charge deposited on the same surfaces, as well as large charge accumulations due to the flames, the polarity of the grid potential is switched periodically. It is believed that the system would find applications in one-story residential homes with the grid mounted in the attic or roof. It would be energized only at nighttime because some of the appliances used during the day in a home may trigger the alarm.