Natural gas is a highly flammable compound that can have some less than desirable effects when inhaled. Natural gas is not poisonous in small amounts, but danger increases as the amount of gas rises. The real danger comes from the possibility of gas igniting, which can happen with even the smallest amount of gas and the tiniest of sparks.
In small concentrations, breathing natural gas is not dangerous. Natural gas contains a high percentage of methane, which is the same substance released by a number of natural process, such as the decay of garbage and compost.
The most noticeable effect of breathing the small concentrations of natural gas associated with a new or slowly leaking appliance is the overwhelming, nauseating smell of rotten eggs. This smell is the chemical mercaptan that is added to the naturally unscented gas to make it easier to detect leaks.
When there is a major or ongoing leak, a high concentration of natural gas can begin to build up. This is particularly dangerous in enclosed areas and inside the home, as breathing this high concentration can have some adverse, but temporary, medical effects.
An individual can begin to feel dizzy, a sensation that can be accompanied by headaches and fatigue. There is no oxygen contained in natural gas, so many of the effects of breathing the gas come not directly from the chemical contained in it but instead from the lack of oxygen the brain and body receive.
Getting out of the area and into the fresh air is the most important way to treat any effects that have developed from breathing natural gas. Typically the headaches and dizziness will begin slowly, giving enough time to get out into the open air. Once the gas is replaced by oxygen, the effects will generally fade.
Prolonged exposure to natural gas can result in a loss of consciousness, which can end up being deadly if the person is not moved to an area with fresh air and oxygen.
Mercaptan is added to the natural gas in order to give it its distinctive smell as a warning of the presence of a leak. Individuals who have an impaired sense of smell can often miss this warning sign and begin to develop the effects of natural gas poisoning without knowing why. As these effects can be caused by a number of different illnesses or conditions, the possibility of a natural gas leak can easily be overlooked. In homes that use natural gas, detectors can be installed to give an audible warning when there is gas in the home.
Elderly individuals often have an impaired sense of smell, and are at particular danger of this. They can also be more susceptible to the effects caused by breathing natural gas, and may lose consciousness faster than a younger individual.