1/1 Gas Sensing Probe Alhead 4 (Ex) Device discontinued Product code: PW-060-A Gas Sensing Probe Alhead 4 is a gas detector designed for the measurement of hazardous gas concentration in potentially explosive atmospheres. It is intended to work in high temperatures and hard-to-reach (inaccessible) places. See full description Product description Gas Sensing Probe Alhead 4 is a gas detector designed for the measurement of hazardous gas concentration in potentially explosive atmospheres. It is intended to work in high temperatures and hard-to-reach (inaccessible) places.