Sewer gas is the common name for hydrogen sulfide gas, which is commonly produced by the breakdown of sewage wastes. Hydrogen sulfide is most often identified by its distinct, rotten-egg-like odor.
At high levels of exposure, hydrogen sulfide can be dangerous, but the rotten-egg odor is detectable at levels far below those which can cause danger. Thus, the smell of hydrogen sulfide gas in your yard should be addressed as soon as it is detected.
People can be exposed to sewer gas in a variety of ways. Cracked floor drains, a leaking or blocked plumbing roof vent, cracks in foundations or other problems can lead to a gas odor.
With septic systems, leaking sewer gas could indicate that pipes in the septic drain field have been damaged, the septic tank is overfull, or the entire system is backed up. Since all parts of the septic system handle wastes that can produce hydrogen sulfide, it can be difficult to track the source of the gas by smell alone.
Have a septic system maintenance professional examine the septic system immediately to determine the source of the leaking sewer gas. As noted, the smell of sewer gas is detectable at safe levels, but it can be difficult to tell if a dangerous level has built up in your yard as a result of the damaged septic system.
Keep people and animals away from the lawn for as long as the smell persists and until its source can be determined and repaired.
Health Effects of Sewer Gas
At low concentrations, sewer gas can cause eye irritation, sore throat and cough, shortness of breath and fluid in the lungs. Long-term, low-level exposure can cause fatigue, loss of appetite, headaches, irritability, poor memory and dizziness.
Hydrogen sulfide can be fatal at high enough levels of exposure, but it would be quite rare for a home to produce enough sewer gas to achieve that toxicity.