Combustible gas concentration detectors; Electric, electronic, or electrochemical oxygen monitors and sensors for environmental use; Electrical and electronic burglar alarms; Fire alarm and emergency evacuation devices, namely, fire alarm control panels, smoke detectors, heat detectors, alarm pull stations, audible and visible notification appliances, strobes, sirens, bells, horns, and speakers; Gas alarms; Gas detectors for detecting the presence of gas; Gas testing instruments; Radiation se...