My husband just bought a used horse trailer (2016) that was only used a handful of times. The LQ and rear tack still smell new, but the horse part smells like an old musty boat!

we left the windows and door open for a few days when we had freezing weather, and then closed it up for the few days of rain we had. We just opened it this morning and it still smells just as bad. 

how can we get rid of that smell? It's equiflex flooring and all of the side mats seem 100% sealed.......

Go to an RV supply place and pick up a product called " Dri-Z- Air" and set 2-3 of the containers in there. That stuff really works!

I use the big tub of damp rid inside the horse area, the tack and I keep one in the bathroom in the LQ. I also keep 1 in my tackroom/feedroom in the barn. They work!