Methane gas is not considered dangerous to humans by inhalation. Exposure to methane gas in air with low oxygen levels may cause dizziness, headaches and a feeling of fatigue with no lethal effects.
Methane is a very common greenhouse gas emitted by wetlands and livestock. It is also released into the atmosphere by human activities and natural gas sources. It may be dangerous in heavy concentrations and confined spaces, as it may be explosive if it comes into contact with an open flame.
No long-term health effects are known to be the result of prolonged exposure to methane gas, and it is quickly removed from the body through a variety of bodily functions.