Choose us to explain, the range of combustible gas alarm why is 0 ~ 100%, the lower explosion limit each kind of combustible gas is different, for easy reading, the combustible gas alarm display data is designed into 100 parts, the air volume ratio into the lower explosion limit unit, alarm point setting reading most of combustible gas alarm is between 0 ~ 10 0%L E L, its incremental 1%LEL is a unit change in value, because the percentage standard are the use of LEL to develop the dangerous degree index, alarm limit is generally 10% or 25% LEL, in many instruments setting are set to 25%LEL. But no matter when, once a reading of over 25% LEL means that there may be the risk of burning or abnormal condition, the 25% is the national standard "the petroleum chemical industry flammable gas and toxic gas detection alarm design specification" as the national standard, the alarm number of values for GB50493-2009 regulations, city gas is 20%, the set point more scientific as for the 15%, 30%, 17%, these are not scientific, the absolute security environment must be 0%LEL.