Methane is a colorless gas, mainly methane and carbon dioxide, and a small amount of hydrogen, carbon monoxide, nitrogen, hydrogen sulfide and other toxic gases, in addition, is not conducive to breathe, but because colorless often unnoticed, the biogas pool for a time because of natural hypoxia and asphyxia!
Second a companion to the marsh, with nitrogen oxides and hydrogen sulfide, both of which can cause poisoning and respiratory tract irritation.
First, biogas asphyxia. Because methane is a product of anaerobic glycolysis. So there's no oxygen in the gas. The main component is methane, unable to support the human breath. So this is the main cause of asphyxia,
