Scientific apparatus for signaling, controlling and testing hazardous gases in the air; technical apparatus for monitoring and checking for toxic gases in the air; gas sensors for measuring gas concentration; electronic oxygen monitors for environmental use; self-rescue apparatus, namely, respiratory gas containers; gas meters; gas detectors for detecting the presence of gas; gas chromatography apparatus; metal detectors; altimeters; barometers; gasometers; oxygen regulators; dosimeters; inte...