A variety of active units that sense environmental variables and take various actions are described. In one embodiment, an active unit includes at least one sensor to detect a change in an environmental variable and generate a sensor signal and an action module configured to influence the environmental. The active unit may also include a communication module and a processor module configured to accept the sensor signal and determine if the environmental variable exceeds a threshold and to instruct the action module not to take action to influence the environmental variable, and instruct the communication module to transmit a signal to other active units that the environmental variable has exceeded the threshold.