Sewer gas, something you can't feel or see, has a distinctive odor that alerts your sense of smell. The odor of sewer gas, much like the foul stench of rotting eggs or decaying grass, can make you nauseous. Whenever you walk into a room or confined area, your nose will quickly detect the odor of sulfur dioxide in the presence of sewer gas. Unchecked leakage of sewer gas can impair your health, and a concentrated buildup of gas has the potential to explode.
Check for sewer gas odor near floor drains. When floor drains dry out from infrequent use, the odor of sewer gas may become noticeable.
Inspect your vent pipe. A vent pipe, also called a waste pipe, permits the gasses that rise up from a septic system or sewer line to escape into the air outside the house. Check for odor near cracks or loose joints along the section of pipe that goes through the attic and up through the roof. Climb up on the roof and check for any foreign matter that may have clogged the opening of the pipe.
Examine all unused or rarely used sinks, tubs, toilets and shower stalls. Sniff around to determine if either of these units has a dry trap allowing the infiltration of sewer gas.