Smoke detector for detecting fire to reduce fire hazard in building, has electrometer for measuring electric quantity representing movement speed of electric charges between first and second electrodes to set off alarm

摘要

The detector has a first electrode (12) raised to electric potential with respect to a second electrode (13) to allow electric charges in a drift chamber (30) to move from the first electrode to the second electrode, where an electric field created between the electrodes is 100 times lower than electric field created between the first electrode and a third electrode (11). An electrometer measures electric quantity representing the movement speed of electric charges between the first and second electrodes to set off an alarm when the electric quantity is subjected to abnormal variation. The first and the second electrodes have cylinder form, and the third electrode is arranged parallel to an axis of the cylinder. An independent claim is also included for a smoke detection method.