Experiments on a $50 DIY air purifier (2020)

When the Caldor fire (now 210 thousand acres, 328 mi^2!) was smoking up Placerville, the downtown Home Depot had, at the main entrance, a big stack of 20x24x1-inch #9 furnace filters, box fans, and rolls of tape, with one all constructed sitting on top, running, black with trapped smoke. Kudos to HD for not jacking up prices. It is best to make them with a four inch thick filter, which HD does not stock, and higher than a #9, likewise…

Sadly the state of California bans simple box fans + filters from being sold. For example if you try to buy a "Lasko Air Flex Steel Portable Home Office 3 Speed Air Purifier Machine Box Room Fan with Manual Ergonomic Control Knob and 6 Foot Cord, White" from Amazon you will be greeted with this when you try to order: """This product does not meet California air cleaner regulation requirements, and cannot be shipped to California""" This is essentially like…

A warning: my father read about DIY air filter just like this one, and made a couple of them at home. The fans are not designed to run continuously, and one failed and caught on fire. The living room burnt down but luckily the fire was put out before it took down the whole house. Damage costed orders of magnitude more than the extra few hundred $ from buying a commercial air purifier.