Rotten-egg odor

Sulfur-like odor that may relate to fuel gas odorant, drains, water chemistry or decomposing material.

First distinction

Note where the odor is strongest, whether it appears with rain, wind, heating, plumbing or ventilation, and whether closing a door changes it.

Do not mask the pattern

Fragrance can make the pathway harder to identify. Record timing before cleaning or moving stored material.

Next useful step

Treat this as a safety signal. Stop normal investigation and follow the applicable emergency or professional guidance.