What can be mistaken for gas smell in a house?

A wide variety of everyday household substances, biological waste, and mechanical anomalies can easily be mistaken for the pungent rotten egg smell of a natural gas leak. Common biological culprits include rotting organic food waste trapped inside a kitchen garbage disposal or sink drain, spoiled potatoes or onions hidden in pantry bins, and sulfurous sewer gases rising from an unprimed, dry plumbing P-trap or sewer vent stack. On the mechanical and electrical side, overheating plastic wire insulation, a failing refrigerator compressor relay, or a burning appliance motor winding can emit sharp, chemical odors that closely mimic mercaptan. Furthermore, sulfur-bearing well water, dead rodents trapped inside wall voids or ductwork, and certain cleaning agents can produce distinct sulfurous scents. You can verify whether an odor is gas by using a professional gas detector.