You can learn more about filter rating systems from LAist here. All you need is a box fan, good air filters and some duct tape, and you're in business. NPR has previously posted a design and guide ...

You can learn more about filter rating systems at member station LAist. An air quality map shows a large part of the Los Angeles metro area with "unhealthy" air, due to large wildfires fueled by ...

“And it comes out of the top, so it filters in and out.” Each system consists of a box fan, four furnace filters, duct tape, and cardboard, costing roughly $60 to make. The Environmental ...