Mystery Interior Odor Solved
I've had the same mystery odor in my 2009 Flying Cloud (purchased new in 2010) as others on the forum and I've never seen a solution listed. I tried ozone machines and a variety of other treatments and nothing worked. Our solution was to light candles and open the windows while we camped.
Well, I've figured it out - at least for my Airstream. We replaced our rock hard, OEM mattress last month with a great new foam mattress and, amazingly, the odor has disappeared. My guess is that a percentage of the cheap 100% polyurethane beds that are used in the trailers continue to emit gassing that results in the strange smell.
My advice for those still dealing with this mystery? Spend the $700 for a custom-cut, comfortable new RV mattress from MattressInsider.com. You'll sleep much better and your camper odors will disappear.