Introduction Congratulations on your purchase of the Extech EZ40 Combustible Gas Leak Detector. The EZ40 detects the presence of combustible gas and nuisance vapors (Natural Gas, Methane, Ethane, Propane, Butane, Acetone, Alcohol, Ammonia, Steam, Gasoline, Jet Fuel, Hydrogen Sulfide, Smoke, Industrial Solvents, Lacquer Thinner, Naphtha) in concentrations as low as 10% LEL for Methane and alerts the user with audible and visual alarms.