I had the same problem. My filter was not the rating it promised. My fan would pull to hard. It got rid of some smell but when it got bad last grow I had a good idea.
Ozone generator. I nuked it. I got the uv model used for 50 bucks on ebay. I took the lid off and stuck it in my exhaust. SO on bad days I just turn the ozone on. But only when I am not in the room! It can mess you up bad right off the bat. Lol, just common sense. Weird dreams tho. . .
Make sure you get the uv models not the corona discharge model that makes nitric acid as a byproduct which will kill plants.
Cheap easy, or you could get another filter so then you have 2. Get a thick packed bed model. Some are more packed if you read the specs.