1. An apparatus for monitoring an environment comprising: a housing; at least one photon sensing element responsive to incident photons having a wavelength in a single predetermined range which are indicative of an external environmental condition forming at least one output signal indicative thereof; wherein the at least one sensing element is mounted at one of in or on the housing such that photons originating within the environment external to the housing are incident thereon; at least a second sensor, carried by the housing that senses a different environmental parameter and forms at least a second output signal indicative thereof; a controller that receives the signals and, in response at least to those signals, produces an output signal indicative thereof.