Listen man, spend the money on a nice carbon scrubber. It is totally worth it. I have a nutty neighbor and twice the cops have come to the door asking about him in the past 2 weeks. If I had a home made jobber I would be sitting in jail instead of waiting for my harvest to dry. I did build a DIY filter for my dry box but they do not smell nearly as bad as they did while flowering or vegging. I started in a guest room and it stunk up the whole house. When I harvested it stunk up the whole house and my yard, I decided to open my tent so the scrubber would clean out the air in the room and it worked, no more smell. This is 1 area you shouldn't skimp.