Detailed Product Description Description:. Alarm mode: give an alarm warning while alarm density reaches: coal gas: 1000 ~ 5000 ppm, LGP: 1000 ~ 5000 ppm, natural gas: 1000 ppm ~ 5000 ppm. Working mode: independent & compatible mode: work solely at party, room etc.. Siren: > 90 db. Strict method with good qualitySpecification:. Operating voltage: AC 220 V, or AC 110 V, DC 12 ~ 20 V. Working ...