Alarm hushing and pre-alarm hushing states may refer to a user-instructed deactivation of an alarm or a pre-alarm. For example, in one embodiment, a user can press a button (not shown) to silence an alarm or pre-alarm. In another embodiment, a user can perform a hush gesture in the presence of the hazard detection system. A hush gesture can be a user initiated action in which he or she performs a gesture (e.g., a wave motion) in the vicinity of system 300 with the intent to turn off or silence a blaring alarm. One or more ultrasonic sensors, a PIR sensor, or a combination thereof can be used to detect this gesture. The gesture hush feature and systems and methods for detecting and processing the gesture hush feature are discussed in more detail in United States Publication No. 2015/0029019.
Post-alarming states may refer to states that multi-criteria state machines 310 can transition to after having been in one of alarming states 330 or one of pre-alarming states 340. In one post-alarming state, hazard detection system 300 can provide an “all clear” message to indicate that the alarm or pre-alarm condition is no longer present. This can be especially useful, for example, for CO because humans cannot detect CO. Another post-alarming state can be a holding state, which can serve as a system debounce state. This state can prevent hazard detection system 300 from immediately transitioning back to a pre-alarming state 340 after having just transitioned from an alarming state 330.