FIG. 3 shows an illustrative block diagram showing various components of hazard detection system 300 working together to provide multi-criteria alarming and pre-alarming functionalities according to various embodiments. As shown, system 300 can include sensor data 302, hush detection events 304, transition conditions 306, threshold adjustment parameter 307, multi-criteria state machines 310, clock 312, other states 320, alarming states 330, pre-alarming states 340, alarm 350, display 352, and speaker 354. Also shown are several communication links 370, each of which may have unidirectional or bidirectional data and/or signal communications capabilities. Multi-criteria state machines 310 can control alarming states 330, pre-alarming states 340, and all other state machine states 320 based on sensor data 302, hush detection events 304, transition conditions 306, clock 312, and other criteria, and alarming and pre-alarming states 330 and 340 can control the output of alarm 350, display 352, and speaker 354. Alarming states 330 can include multiple alarming states (e.g., one for each hazard, such as smoke alarming state 331, CO alarming state 332, and heat alarming state 333) and pre-alarming states 340 can include multiple pre-alarming states (e.g., one or more for each hazard, such as smoke pre-alarming state 341 and CO pre-alarming state 342. Other states can include, for example, idling states, monitoring states, alarm hushing states, pre-alarm hushing states, post-alarm states, holding states, and alarm monitoring states.
