Review on 4 Gas Monitor Detector With Alarm - Handheld Professional Multi Gas Meter For O2, H2S, EX, And Co, Featuring Color Display And 2500MAh Battery, In Orange by Ryan Carter

This meter responds within seconds to small and large changes in the 4 measured gases. You can easily test the O2 meter by just breathing on it which will set off the default alarm for low oxygen levels (the photo I attached is of the alarm going off from this particular test - it is both an audible and visual alarm).I also tested the explosive gas by putting it by my propane grill and it detected the explosive propane. However, the default threshold for the alarm might need to be set a bit lower because even though I smelled propane and it detected a 10% LEL concentration, the alarm did not sound. This is something that can be configured though.The CO alarm was tripped within seconds of placing the meter near my running car exhaust. The car exhaust and even your breath can produce measurable H2S levels. So I assume that is working as intended as well.The only downside is that this detector does not have a great battery life and will start warning you of low battery after 12 to 14 hours. But you need it to run for long periods of time, you can just leave it plugged in to run continuously. Overall I am very happy with how it performs and would recommend it!