A mixed-voltage inputoutput buffer includes an output buffer circuit. More specifically, in the in-use condition, the blade fixing element preferably projects through or otherwise engages the blade to prevent the blade from rotating in either direction. Dynamic measurement of ozone concentration with time whilst ultraviolet irradiation is pulsed enables each gas concentration to be calculated without requiring input gases to be scrubbed. In some implementations, the host application is a media player. If the validation agent is compromised, the second processor causes the first processor to communicatively decouple from a network.