Any tips for getting a smell out from a sofa?

[Melyn]

So I've been given a sofa by a friend, it looks okay, no stains, looks like it hasn't really been sat on however there is a "wet dog" smell that Febreze will not shift.... Where the smell is coming from is the seat part of the sofa which cannot be removed so I can't put it in the washing machine.... Any tips on things I can try? Thanks

Bicarbonate of soda apparently eliminates smell. Perhaps brush it in?
Don't wash the covers you might not get them back on.

I can't remove the covers anyway as they're attached to the sofa.. I did look into bicarb but wondered how well it works..

Yes bi carb should work. Sprinkle on, leave ideally over night then Hoover.

Maybe the smell is because the previous owners tried to hand wash in situ before giving it to you as the covers aren't removable, hence the smell is damp not doggie?
Try the bicarb.

Not sure, they do have dogs around occasionally. If bicarb doesn't work what can I try then? Thank you

Next, I would try vinegar. I use it with smelly laundry.

You can hire upholstery cleaners for a wet clean. It's the only thing that got the smell out of ours (nothing nasty just someone else's house smell!) didn't take long to do and came up really fresh. Frebreeze didn't cut it

Thanks all,
Going to try bicarb a couple of times, then white vinegar then if all else fails I'll get an upholstery cleaner to come out. Thank you for the suggestions!