I developed this design after living downwind of a refinery and in the apartment above a smoker for a year. It's simple and it works. The idea is to address two types of air pollutants: particulate matter (like dust, dander, ash from smoke, etc.) and VOCs (gasses, not particles). Particles can be removed with a mechanical filter, just like you can remove a fish from a fish tank with a net or lint from the exhaust on your drier with a lint trap. Gasses cannot be trapped with filters like this though. Gasses must be chemically, not physically removed. Carbon is great for this purpose because it will "adsorb," or stick to, lots of different kinds of gasses that you shouldn't be breathing.
An ideal system removes all particles and all toxic gasses from your air. This system doesn't do that, but it will help, and it's waaay more affordable than an industrial air cleaner.
First, we want to get the particulate matter out of the air with a physical filter. Then, we want to run the remaining gasses over carbon so some of the toxic gasses will be adsorbed out. Here's the easiest way I've found. I drew it during a morning college class to try to stay awake.
