How do I cure a “musty” odor?

We bought a 12 year old motorhome 4 years ago... The PO didn't heat it during winter storage and it had a little musty smell. I kept the heat on for months and it is gone.

First thing I did was look for any possible entry points of water or condensation and then eliminate them (only thing I found was a leaking porthole frame that needed tightening).

I installed a 4" solar Day/Night powered vent on the foredeck (about 18" back from the main hatch) and set it on "Extract" and it pulls out air from the cabin at cabin ceiling height.
https://www.hodgesmarine.com/macn20...MIgs2ZsfKS9QIVNhXUAR0BUwIBEAQYASABEgKsYPD_BwE

Then I have a automatic running a dehumidifier set a 50% relative humidity with the drain hose emptying into the galley sink. I also placed a small 120v computer fan on the cabin table to move the air around.

I leave head door and all closet doors open for air circulation.

No musty smells, boat is dry, linens and bedding smell fresh.

ocgrant said:

Find the source is the first attempt. Water in bilge, shower sump, sewer lines old? Otherwise all the rest is just masking

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Yup, you need to find the source of the problem.....and moisture is the problem. I know if it was my boat I would be digging into every nook and cranny to find the source of that moisture. And if I were a betting man I'd put my money on the compartments under the saloon.

I had a God awful smell last summer after buying the boat...numerous attempts to mollify using air fresheners, deodorizers, you name it...turns out it was one of those oil absorbing pads that was way back in the bilge and smelled ghastly.

After you find the cause of the odors fix that, then rent an ozone generator and run that. After that do what others have suggested that works.

Sometimes that smell is embedded in the foam cushions in the cabin. Take one of the cushions outside and smell it. If you get that odor from the foam, you can try taking the covers off and cleaning them. Leave the foam itself outside in the sun for a day and see if that helps.

A steam cleaning machine will kill the spores in the foam and fabric. Amazon has them around 100 bux or so.

Some suggestions for the root cause, the AC bases that hold water and do not drain right are one of the first causes, the shower sump sometimes dries out and odor filters back. As mentioned any standing water in the bilge might cause cabin odors, but the fire wall should stop that. Also as mentioned clean the carpet really well. But the AC base/drains are usually the biggest culprit.

One thing I do at the start of every season in put a little bleach in the AC drains and let sit over night then flush with fresh water or cleaner that smells nice. I also pour bleach in the shower and let stand as well. This keeps the lines clean and free. You can use other cleaners like oxiclean and the like (special mix of poopy powder etc.) I use bleach as I am ok with that and it works. I then use a febreze product in the AC return vents and have zero issues all season long. Another thing that helps in season is leaving the AC on full time, not a dehumidifier or that setting on the AC, but the AC at a reasonable temperature, low/mid 70's.

Febreze all the soft upholstery and baking soda in any enclosure. Also, as stated find any source of offensive smell and remediate.