Sealing Off a Room With Tape and a Purifier: Does It Really Work?

An essay floating around the internet suggested something intriguing: that you might be able to improvise a "bioshelter" — a room full of clean air — using stuff people already own. The idea is that if you push filtered air into a room, the air leaks out through the cracks instead of leaking in, so germs and smoke stay outside. Jeff Kaufman, a tinkerer who writes on the blog LessWrong, was skeptical, so he tried a stripped-down version himself using a HEPA purifier (a fan with a filter that catches tiny particles).

His first test was the best case. He taped a trash bag over the purifier's top and measured how hard it pushed: 83 pascals, a respectable number. Then came reality. He taped plastic sheeting over a doorway. It billowed nicely, but he could feel air escaping through countless tiny gaps, and every trip in or out meant resealing everything with tape. So he cut a hole in his wall, mounted the purifier sideways — it promptly fell apart, and he had to hold it together with baling wire — and taped the edges. The result: 12 pascals, roughly a seventh of the bag test. He admits his measuring tool is only rated for accuracy at 5 pascals, so he's ordered better equipment to check.

There's a bigger unknown, too. Nobody actually knows how much pressure you need to keep contaminants out. It depends on wind speed, and on whether the leaks in your walls lead straight outside or wander through the building's insides. He also notes the test is a rough one, not a scientific study.

So should you build one? Not yet. But the experiment hints at where cheap home protection could go: if pressure sensors end up in phones, anyone could check how leaky their safe room really is.