By itself, methane is not toxic. It is extremely flammable and will cause an explosion; it will also kill you by asphyxiation if it leaks into an enclosed space and deprives you of oxygen. But methane only becomes poisonous when it forms part of another gas and is subject to certain circumstances. The bad news is that this happens quite often.

How Are People Exposed to Methane Gas?
Exposure to pure methane is by breathing, drinking, eating and touching, and many of us will have experienced all four.

1. Inhalation
   We may have breathed the gas when it has entered a building or home by issuing from a crack in the foundation or via a sewer trap. Or we may have unwittingly inhaled methane when we passed close by a septic tank, sewer, manhole or farm waste pit.
2. Ingestion
   It is possible but doubtful that you have drunk a glass of water contaminated with methane. Methane created naturally underground can certainly make its way through the soil and into a water reservoir or lake, but even if this happens, the gas tends to evaporate quickly. Similarly, a young child may eat dirt that has traces of methane. But the levels of exposure are low and there are no known effects on the body.
3. Touch
   As for touching, methane gas has trouble passing through the skin, so you are unlikely to absorb it. But if methane does enter your system, by whatever means, your body will remove it swiftly through your breath, blood and urine. And medical research on the issue shows that even after years of exposure to methane, our reproductive and internal organs remain unaffected.

So after all this, you might feel entitled to breathe a sigh of relief and move on. But I wouldn’t dismiss methane detection so easily if I were you. Methane is not a safe gas and you dare not ignore it. Why else do we place fans under buildings to remove methane emissions that we have discovered are seeping from the ground? The reason is not just the flammability of the gas but its properties as an asphyxiant: methane displaces oxygen, and in an area without ventilation will cause suffocation.

Identifying Methane Exposure by Symptoms
Is it possible, then, for us to identify methane gas before we succumb? Perhaps. Impending suffocation may give rise to symptoms such as headaches and dizziness as the amount of oxygen in our bodies depletes. This was a problem among some of the students at the New London School before the methane ignited and caused terrible destruction and death (see Historical Events Where Methane Gas Has Killed). But it is just as likely that we will feel nothing until our brain registers a deficiency of oxygen and causes us to gasp for air. By then, however, it is usually too late for us to do anything other than collapse.

Carbon Monoxide is a Byproduct of Methane
This problem of ventilation is critical when natural gas (which is 97% methane) is burned in our homes, offices and businesses. When natural gas is burning in our boilers, heating radiators and water, and for some reason has an insufficient air supply, carbon monoxide is produced.

Carbon monoxide is colorless, non-irritating, odorless, tasteless and deadly. At 200 ppm (parts per million), you develop a frontal headache after just one to two hours of exposure. At 1600ppm (just 0.16%), you are dizzy, have a headache and feel nauseous within twenty minutes; you are dead in under two hours. At 12800ppm, you are lifeless in less than three minutes.

40,000 people each year in the United States require medical attention after inhaling carbon monoxide fumes, and many of them suffer permanent damage to their heart muscles. 500 people a year die as a direct result of carbon monoxide exposure.

Confusion About Symptoms
The symptoms are easily confused with other conditions such as chronic fatigue syndrome, depression, flu, and migraines. Other more advanced symptoms you may experience include confusion, convulsions and unconsciousness. At the clinical level, you may have tachycardia (rapid heartbeat) and hypertension (high blood pressure).

Carbon monoxide also affects the central nervous system, causing hallucinations and a heightened emotional state. This can give rise to sightings of “ghosts” and apparent supernatural occurrences.

The gas behind all this is methane, which in the form of natural gas is piped into some 67 million homes across America. We shouldn’t be scared of it – but we should certainly be wary.