In the wake of the Japanese nuclear plant melt-down situation, I called a safe room manufacturer for a hand cranked air filter. It was over $2,000. Too much. I did learn that you need both particulate (HEPA) and gas (carbon) filters. I have jury-rigged an NBC air filtration system. Here it is:
Go to a hydroponics store or find one online. Yes, the one’s that people go to in order to grow marijuana. You will need an inline fan. I used a continentalfan.com AXC150B-C fan. It is a little more expensive but German engineering costs more. (Quieter too). You will need a carbon filter. I used a Can-33 activated carbon filter (made in Canada) You will need a 6 inch Greenhouse HEPA filter. It can be washed and reused but only put it back in your system if it is completely dry. You will need a can flange 6″.
Total cost about $450.
The HEPA filter is attached to the air intake of the fan. The Carbon filter is attached to the air exhaust of the fan.
This is a recirculating system, not an overpressure system. At 300 CFM, it will clear the air of a 10’x10’x10′ room in 3 minutes and 20 seconds.
It stands completed at 30″ high and 16″ wide at it’s widest point. It uses 130 watts of current. – SF in Hawaii
JWR Replies: A HEPA filter system with air pushed by an electric fan is best suited to someone that has a fairly capable alternative energy system. Anyone without a large power source that can be relied upon for weeks should substitute a hand-cranked fan. And even those that do have a large alternative energy system should always have a “Plan B”: An electric filtered ventilation system should have a hand-cranked or pedal-cranked backup. There are too many potential points of failure to entrust our lives to continuity of electric power.