by Quick answer: Sprinkle baking soda over the mattress, leave it several hours (longer for strong odors), then vacuum it up. Air the bed out with open windows and, if possible, sunlight. A new mattress's chemical smell fades in days; a persistent musty smell can signal mold.
By the MattressNut editorial team · Updated June 2026
Mattress Smell — The Short Answer
Two different smells need two approaches. A new mattress smells from off-gassing — harmless and gone in a few days with airflow. An old mattress that smells musty or sour usually has trapped moisture, and that can mean mold or mildew. Baking soda, air, and sunlight handle most odors; mold needs more attention.
What to Do
| Step / Factor | Detail |
|---|---|
| Deodorize with baking soda | Sprinkle a generous layer, leave 4+ hours (overnight for strong odors), then vacuum thoroughly. It absorbs odor rather than masking it. |
| Air it out | Open windows, run a fan, or move the mattress near sunlight. Fresh air and UV both cut odor and surface moisture. |
| New vs. musty | New chemical smell = off-gassing, fades in days. Musty or sour smell = trapped moisture, check for mold. |
| Spot-treat stains | For odor from spills or sweat, an enzyme cleaner breaks down the source. Blot, don't rub, and dry fully. |
Practical Tips
Always dry the mattress completely — leftover moisture is what creates musty smells in the first place. For protein-based odors like sweat or urine, enzyme cleaners outperform baking soda alone. If you see black or green spotting along with a persistent musty smell, that's likely mold, and a moldy mattress is generally not worth saving.
Our Recommendation
Surface odors clear up easily, but a deep musty smell or visible mold in an aging mattress is a health reason to replace it. If yours is old, sagging, or moldy, a fresh mattress is the cleaner fix. The Saatva Classic includes free white-glove delivery and old-mattress removal, so the smelly one is taken away at delivery.
See the Saatva Classic and its 365-night trial
The Bottom Line
Baking soda, fresh air, and sunlight remove most mattress odors. Tell new off-gassing (temporary) from musty mold smell (a replacement signal), and always dry the mattress fully.
Bottom line: Deodorize with baking soda and air it out; a persistent musty smell may mean mold and time for a new mattress.
Related: our full Saatva mattress review.