Was the previous owner a smoker of tobacco or other? If so, the odor most likely penetrated deep into the walls. Smell the walls and see if that is location of odor. What kind of odor is it? Please describe best you can.

If the smell is similar to rotten eggs, that can be a sign of a natural gas leak. Another common odour is a "dirty sock smell", which can be from mold and mildew build up on an A/C coil.

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I really really wish I could pin point it to cigarettes but it is definitely not a smoke smell. More of a sickingly sweet smell. We thought it might have been a dead animal but after checking under the trailer we found it wasn't. it is definitely in 1 room and the smell is overwhelming at times. We do not believe it is anything in the vents because the smell isn't in the rest of the trailer. Next week we plan on cleaning the walls and seeing if that helps. It's just so annoying and definitely disgusting.

Thanks for your responses.

Well, it might not be from tobacco, could be from someone smoking "pot". One day recently we smelled something in our backyard and our daughter visiting told us it was the neighbor smoking "pot". It had a sweet smell to it.

That's a thought. I am really hoping the wall cleaning will do the