Wearing high-grade filter masks can help protect against the novel coronavirus. But after a few hours, these tight-fitting devices can also make it really hard to breathe. N95 respirators, for example, are famously good at blocking viral particles—but they can also reduce the amount of available oxygen by up to 20 percent. Now some Stanford University researchers are addressing this problem with a portable device that pumps pure O2 directly to the wearer.
