SCOTT DETROW, HOST:

It’s almost summer, and if recent years are a guideline, that means heightened threats of wildfires. Billowing smoke from wildfires can cause dangerous air quality levels. Air filters in homes can help manage smoke, but what if you don’t have one? NPR’s Alejandra Borunda set out to see if it is possible to make your own air filters.

ALEJANDRA BORUNDA, BYLINE: The short answer is yes. You can build a DIY air filter in less than 30 minutes with stuff that you probably already have in your house.

ELLIOTT GALL: My name is Elliott Gall, and I am an associate professor in the department of mechanical and materials engineering at Portland State University.

BORUNDA: He’s the designer of this air filter called The Cocoon. Graduate student Brett Stinson explains.

BRETT STINSON: It’s pretty simple. It’s just a fabric filter. This is cotton batting and a box fan.

BORUNDA: Basically, just a tube of fabric attached to a box fan. Gall says it’s an old technology called a baghouse filter.

GALL: And it essentially is a piece of fabric that you force air through that filters out particulate matter.

BORUNDA: To me, it looks like a blobby, puffy, 8-foot-long sausage. But it works almost as well as air filters you can buy. Here in the lab up in Portland, we load up a sealed bedroom-sized area with smoke and start The Cocoon running. Within about 10 or 15 minutes, the air is pretty much clear. And my partner and I set out to build a Cocoon for ourselves.

This is Ali (ph) and Alex’s (ph) attempt to make a box fan filter.

Gall sent me a PDF with instructions. First, we track down a standard box fan, like the ones they sell in just about every hardware store. Then you need a big piece of fabric that’s 72″ wide.

Here’s the measuring tape.

That’s important because that size will fit neatly on the fan.

(SOUNDBITE OF MEASURING TAPE PULLING AND RETRACTING)

BORUNDA: Gall used cotton batting like the stuff inside of quilts.

But we don’t have that, obviously. I’m not a quilter. What we do have – and they say is OK – is sheets. Cotton or linen work best, they say.

We found an old, full-sized flat sheet in the back of a cabinet. That was perfect. Bigger ones could work, too, but you’d have to cut them down. So then we took the sheet, and we folded it in half lengthwise, like a giant hot dog bun. And then I attached the two long sides together very carefully with duct tape.

(SOUNDBITE OF DUCT TAPE PULLING)

BORUNDA: You end up with this big, long tube. And then you take some rubber bands or hair ties or whatever and twist them around one end of the tube – like you’re putting it in a little ponytail.

(SOUNDBITE OF RUBBER BAND SNAPPING)

ALEX: That works.

BORUNDA: And now we’re on to the last step. We slip the open end of the fabric tube around the edge of the box fan and duct tape it in place.

(SOUNDBITE OF DUCT TAPE PULLING)

BORUNDA: But make sure you don’t make this mistake.

I covered up the controls. So that’s a little bit silly. That was my mistake. Don’t do that.

Then we turn it on.

(SOUNDBITE OF FAN WHIRRING)

BORUNDA: Ooh. And we have inflated a giant blue tube.

It poofs up and looks exactly like one of those slinky tubes little kids crawl through. Gall says it works best if you can run it in rooms that aren’t too big, like overnight in a bedroom, for example. For NPR News, I’m Alejandra Borunda. Transcript provided by NPR, Copyright NPR.

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