Microprocessor-based combination smoke and carbon monoxide detector having intelligent hush feature

A microcontroller-based hazardous condition detector having an intelligent hush feature is presented. The microcontroller controls the operational mode of the detector by monitoring a single user-actuated switch, the inputs from a smoke chamber and a carbon monoxide detector circuit, and the current operating mode of the detector. When in a normal or no-alarm mode, actuation of the switch will cause the microcontroller to place the detector in a test mode of operation. If the detector is in a carbon monoxide alarm mode, actuation of the switch will act to reset the accumulator function of the microprocessor for the carbon monoxide alarm sensing. If the detector is in a smoke alarm mode, actuation of the switch may place the detector in a hush mode if the level of smoke is sufficiently low, or will have no effect if the level of smoke is too high. Once in the hush mode, actuation of the switch will place the detector into the smoke alarm mode. The microcontroller will also place the detector in the smoke alarm mode if the level of smoke increases beyond a certain limit, and after the expiration of a hush mode time limit. To coordinate this operation, the sensitivity of the detector is not changed in any mode of operation, and the microcontroller monitors both an alarm and a hush threshold.