The WatchGas SST4 Micro gas detector can monitor 4 types of hazards simultaneously. Oxygen deficiency or enrichment, combustible (explosive) gases, carbon monoxide and hydrogen sulfide. In short: O2/LEL/CO/H2S These are the most common hazards in the field of gas detection in industry. The SST4 Micro is a compact, rugged four-gas detector with NFC, induction charging, 1 week operating time and a large, easy-to-read display designed for reliable performance even in extreme conditions.