I once covered a banjo case that smelled with baking soda. After some sitting around, I vacuumed it out and the smell was largely gone.

I can't vouch for this stuff personally, but my mother thought it was pretty good.

Hmmm, it's the mandolin itself that smells bad? Be VERY careful not to spray any deodorants on the finish, it could screw it up. Stick to baking soda, possibly a little bit of Windex (try just a little first!) on the finished areas. Maybe a little baking soda inside too.

If it came to you in a case, the case should be deodorized also.

Good luck.

I got rid of smell by having the banjo sitting a couple of hours in a small room with an ozone generator. Need to be cautious with these devices though and follow the instructions.
Exposure to sun and wind outside will also help but might be bad for the finish. So avoid direct sunlight and noon heat. 

I would stay away from any deodorizer - they are not made for this purpose and can harm the lacquer.

I also think sunshine (not direct) and fresh air will help get rid of the smell of smoke.

I second the recommendation for an Ozone Generator. If you or someone you know has a CPAP, many have a cleaner that is an OG. I have since found car dealers have larger units to remove odors from used car. I have used mine for many different deodorizer tasks. If you can box up whatever you want deodorizer, then run the OG hose into the box.. doesn't even need to be sealed well. In fact, If it is not well sealed it creates a flow-thru effect.
I'll try to add a link here, if you wish to just buy one. Small portable/travel versions aren't that expensive. No luck in finding a share. Just Google: portable cpap cleaner

I purchased a banjo that had been played by a heavy smoker and had a very strong smell to it.

First thing I did was store the banjo out of the case on a stand so it got a lot of fresh air. The smell went away slowly over time and, after a year, it is completely gone.

The case was unsalvageable, though, as the smoke had really gotten into the fabric. Ended up just getting rid of it.

fresh air is the best for the instrument.
for the case scatter baking soda and coffee grounds around inside it. rub them in, ,close it , flip it and rub in the lid.
put it in the back seat of the car for 2 weeks flipping it every day.
vacuum out,, smell be gone.

My friends that own hotels all have ozone generators. If you approach them nice the people at the Holiday Inn might let's borrow one or at least use it there at the facility.

Anyone using an ozone generator ought to be aware of the safety rules.

Here is a good explanation:  https://www.epa.gov/indoor-air-quality-iaq/ozone-generators-are-sold-air-cleaners#harmful-ozone

The first step for the mandolin might be a good cleaning of the exterior, by a non-wax product for instruments such as Virtuoso Cleaner.  Then a week or two out in the open -- not in the case.  

See what the situation is then, before deciding on more severe measures.

As for the case, also give it a week or two open, and recheck.   Then decide what to do next.

Here's a Google search result for "get cigarette smoke smell out of instrument case."

I used baking soda, lots of sunshine, and white vinegar/water to eventually get rid of the musty smell in a banjo and its "The Gibson" case I acquired from an estate reseller going on eight years ago.

Early on when I thought the smell was gone, it wasn't. Kept coming back. I did several rounds baking soda and sunshine. But it was the dilute vinegar that finally got rid of it for good. Vinegar kills mold. 

Plus, I keep some coffee maker water filters -- packets of activated charcoal --  in the case, including one sitting on the banjo's flange. I think this is doing something.

One possible problem. Don't know if this is related or not: The lacquer finish on the back of the resonator has developed some dull spots. I can polish them up briefly, but they come back. I fear I may not have sufficiently neutralized the vineger in the case interior. I'm going to spray the interior with a baking soda solution and set that out to dry in the sun some more, now that warmer weather is here. I'll probably spray a light coat of lacquer on the resonator and hope that holds a gloss.

Consider this a warning in case you try vinegar for the smell in your case.

quote:

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Originally posted by Owen

I can't vouch for this stuff personally, but my mother thought it was pretty good.

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I ditto this. We have it here in New Zealand and I have used to deodorize both a vehicle from a previous owner that once had dogs and old banjo cases.

Let used coffee grounds dry en put it in the resonator for a few hours. Works like a charm.