Threw this together to lessen or get rid of off smells produced by some fermentation. This has probably been done before but hopefully this will help people out there. I live in an apartment in a city and dealing with strong odors isnt really an option for me or my neighbors. lol
Anyway, i started with an 8oz wide mouth squeeze bottle and cut down the top end. It just so happen that the bottles i used were a perfect fit and the airlock cap slipped into the bottle cap perfectly. After that i just popped a few holes in the bottom of the bottle. Lastly you fill the bottle with activated carbon (i went with fine carbon but larger pieces should work) and used a piece of tshirt to keep carbon from getting into the airlock.
All together this setup costs less that $10. Im sure you could do it cheaper depending on what you use. Regardless its a hell of a lot cheaper than a hydroponic style filter and works just as well for the application.