Direct answer
To get rid of persistent musty smells in closets or bedrooms, remove the moisture source, thoroughly dry and ventilate the space, deep-clean porous and hard surfaces, launder all textiles, and keep humidity in the 40–50% range. Use a dehumidifier, odor adsorbers (activated charcoal/zeolite), and replace odor-holding materials if needed. If mold covers more than about 10 square feet or moisture keeps returning, call a professional.
Targets:
- Indoor relative humidity (RH): 40–50% (never above 60%)
- Wood moisture content: ≤12–16% (pin-type moisture meter)
- Closet door undercut: ~3/4" for airflow (or use a louvered door)
Why it happens
A musty odor is usually microbial growth (mildew/mold) fueled by moisture and stale air. Common culprits include high humidity, minor leaks (roof, window, plumbing), condensation on exterior walls, overstuffed closets that trap air, damp textiles, and carpet padding that’s absorbed moisture.
Step-by-step plan
1) Inspect and measure (30–60 minutes)
- Open the closet and bedroom, use a bright flashlight to check baseboards, corners, behind furniture, shelves, and around windows.
- Use a hygrometer to check RH and a pin-type moisture meter on baseboards and drywall near suspect areas.
- Look under rugs and inside closet boxes. Damp cardboard and old leather shoes are frequent odor sources.
2) Ventilate and dry (1–3 days)
- Open doors and windows (weather permitting). Run a box fan blowing out of a window to exhaust humid air.
- Set a 35–50 pint Energy Star dehumidifier to 45% RH in the room; empty/attach a drain hose.
- Create airflow in closets: keep doors open or install a temporary doorstop to leave a 2–3 inch gap.
3) Remove and launder textiles (same day)
- Empty the closet. Wash clothing, linens, curtains, and soft goods. Use hot water if the fabric allows.
- Add 1 cup white vinegar or 1/2 cup baking soda to the wash to neutralize odors. Dry completely—sun-drying helps.
- Replace cardboard boxes with sealed plastic bins and elevate them off the floor.
4) HEPA vacuum and clean hard surfaces (2–4 hours)
- With an N95 mask, HEPA-vacuum shelves, walls, baseboards, and floors using a soft brush attachment.
- Wipe all surfaces with one of the following (do not mix chemicals):
- White vinegar: 1:1 with water for walls and shelves.
- Borax: 1/2 cup per gallon warm water for porous wood and drywall paint films.
- EPA-registered antimicrobial (e.g., botanical cleaners) per label.
- For bathroom-adjacent closets with glazed tile, a diluted bleach solution can be used on nonporous tile only. Avoid bleach on drywall and unfinished wood.
- Let everything dry thoroughly with fans running.
5) Address sources and seal (variable)
- Seal gaps where humid air or pests enter: caulk small trim gaps; low-expansion foam around pipe/wire penetrations.
- If you find prior water stains but no active moisture, seal odors with a shellac-based primer (e.g., BIN) on cleaned, dry surfaces; then repaint with quality interior paint.
- If carpet or pad smells musty after drying, consider replacing the pad or the carpet. For subfloor odors, apply an odor-blocking primer before reinstalling flooring.
6) Long-term prevention
- Maintain RH at 40–50% with a dehumidifier or by improving whole-home ventilation.
- Improve closet airflow: undercut the door about 3/4 inch, swap to a louvered door, or add a passive transfer grille.
- Keep closets loosely packed; leave a few inches between items and walls.
- Place odor adsorbers: bowls or sachets of activated charcoal or zeolite; replace monthly.
- Change HVAC filters regularly (MERV 8–11) and verify a supply register serves the room.
Tools and materials
- Diagnostic: hygrometer ($10–$20), pin-type moisture meter ($30–$60), flashlight, inspection mirror
- Drying/airflow: box fan or air mover, 35–50 pint dehumidifier ($150–$300)
- Cleaning: HEPA vacuum (purchase or rent $30–$50/day), microfiber cloths, soft brush, buckets
- Solutions: white vinegar, borax, EPA-registered antimicrobial cleaner, baking soda
- Odor adsorbers: activated charcoal or zeolite ($10–$25)
- Repairs: paintable caulk, low-expansion spray foam, shellac-based primer ($20–$50/quart), interior paint
- Storage upgrades: plastic bins with gasket lids, cedar blocks (optional scent and pest deterrent)
- PPE: N95 respirator, nitrile gloves, safety glasses
Safety considerations
- Wear an N95, gloves, and eye protection while HEPA vacuuming and cleaning.
- Never mix bleach with vinegar or ammonia. Ventilate during cleaning and drying.
- If visible mold exceeds ~10 sq ft, or if you have health sensitivities, stop and call a mold remediation professional.
- Avoid consumer ozone generators; they can be hazardous and often mask rather than resolve odors.
Tips for best results
- Pull furniture 2–3 inches off exterior walls to reduce condensation and allow airflow.
- Use a continuous, low-speed bath fan or a smart dehumidifier in humid seasons.
- Label laundry routines: don’t park damp gym clothes or towels in closets.
- For leather goods, wipe with a vinegar-damp cloth, dry fully, then condition.
- If you must keep cardboard, place it on wire shelving, not on carpet.
Common mistakes to avoid
- Masking odors with fragrance sprays instead of fixing moisture.
- Closing the cleaned area before it’s dry—odor returns.
- Using bleach on porous materials like drywall or raw wood.
- Overpacking closets, which traps humid air and reintroduces mustiness.
- Reinstalling unwashed or damp items back into a freshly cleaned closet.
When to call a professional
- Recurring musty odor with RH under 50% (indicates a hidden leak or building envelope issue).
- Visible mold patches >10 sq ft, or mold inside wall/ceiling cavities.
- Persistent moisture readings above 16% in wood or repeated wet drywall.
- Suspected roof, window, or plumbing leaks; or crawlspace/basement humidity problems affecting upper rooms.
With a moisture-first approach, thorough cleaning, and better airflow, most musty closets and bedrooms can be restored within a weekend—and stay fresh for the long haul.