A floor drain usually has a water seal that keeps sewer gases from entering the room. A trap primer supplies a small amount of water to that trap so it can retain its seal when the drain is rarely used.
Look at when the odor returns
If the odor fades after water enters the drain but comes back during long periods of disuse, a dry trap may be involved. If it returns immediately or appears at several fixtures, report that pattern. There may be a different issue with drainage or venting.
Ask how the trap gets replenished
A plumber can determine whether the drain has a primer, how it receives water, and whether the device is working. For a commercial space, share any floor plan or fixture schedule that identifies the drain and nearby water connections.
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