Does anyone know if a gas mask would filter out Ebola?
If the filter is a P-100 rated filter, it should. full face protection helps keep you from getting the virus in contact with facial openings (nasal, oral, eyes) as well.
A properly fitted N95 mask would work, because it is designed for particles smaller than Ebola viruses. Distance from an infected person is even more important.
N95’s are pretty common, and block 95% of particles that are 0.3 microns in size or larger. That is 300 nanometers, and the Ebola virus is about 80nm in diameter and 800-1000nm in length. So if the N95 is properly fitted, it should block all of the virus.
notes: ear-loop surgical masks are not designed to protect the wearer, but to protect someone else from being infected by the wearer. So an N95 has a bowl shape to cover the nose and mouth.
In addition to protecting the nose and mouth, lab glasses keep the virus out of the eyes. From there, the biggest concern is physical contamination, of mostly the hands.