The production of carbon monoxide in the underground garage mainly comes from the car engine. When the engine is running at idle speed, due to insufficient gasoline combustion, it will produce exhaust gas containing a large amount of carbon monoxide. The underground parking lot is a closed environment. Vehicles enter and exit frequently, and the exhaust gas is not easy to be discharged. It is easy to accumulate a large amount of carbon monoxide gas, which causes the parking lot to be filled with choking smell and damages people's health.