The filter mask was uncomfortable, cutting into her face.

"One big problem with a conventional filter mask is that it sits very heavy on your nose," he said.

See that filter masks are distributed to the populace.

They stared upward, their faces hidden by filter masks.

Breathing the air with the aid of nothing more than a filter mask.

So there was still too much CO2 for humans to tolerate without filter masks.

Montenegro felt for a locker near the door and retrieved two filter masks.

He peeled back a filter mask to reveal grayish-pink skin underneath.

The militia moved inexorably into the clouds, breathing through their filter masks.

Beam down a set of standard filter masks, one for each of us.