Patent ID: 7532117
Filing Date: 2009-05-12
Classification: G08B

Abstract:
1. A hazard alarm for detecting a hazardous condition for an area, comprising: a detector which measures a hazard parameter; trigger logic which triggers an alarm state when the measured parameter reaches a predetermined alarm threshold, the alarm state being maintained until a reset is successfully performed, the predetermined alarm threshold indicative of a hazardous condition in the area and used for triggering the alarm state from a non-alarm state; and reset logic which, upon a reset command, resets the alarm state to the non-alarm state if the measured parameter does not exceed a predetermined reset threshold, and which inhibits resetting of the alarm state to the non-alarm state if the measured parameter exceeds the predetermined reset threshold, the predetermined reset threshold being sufficiently different from the predetermined alarm threshold so as to be indicative of a continuing hazardous condition in the area, the hazardous condition indicative of a hazard in a first part of the area and the continuing hazardous condition indicative of the hazard in a second part of the area, the alarm threshold and reset threshold being sufficiently different to prevent reset of the alarm state when the hazard continues to pertain in the second part even after the hazard in the first part ceases.