Smell/odor in trailer

Thanks for the opinions advanced! I appreciate very much!

Here is some additional info esp in regard to the comments/questions presnted so far:

The trailer has never been smoked in

I completely flush and keep both grey and black tanks clean. Mostly use the blue liquid for the black tank.

According to Crossroads, my trailer doesn't have the vent values, but the grey tanks are vented through the roof and out under the refrigerator vent. (BTW, that was the first thing, I checked)

No dead animals (that smell would be really bad)

I keep thinking the glue and/or material has chemicals still residing.
Its really frustrating to not be able to figure this out


I will try both the Charcoal and perhaps the ammonia in a tray. The air freshener idea should help, but I would think that would only mask the odor; not eliminate it.

Perhaps an air purifier would help, but wouldn't that require ele to be present all the time?

Thanks again and keep the thoughts coming.