Even if you are, a gas mask is total overkill.
A simpler solution is simply not to touch the saliva, mucus, feces, blood, or various other bodily
fluids of an infected person and then touch yourself. Even then, a common N95 particulate mask will stop Ebola particulate from penetrating it. Of course, I reserve the right to point and laugh at anyone walking around the streets of North America or Europe wearing a mask because of a localized Ebola outbreak in Africa.
Despite the fact that it is a particularly nasty virus with a high mortality rate - which has more to due with the places that usually experience outbreaks, not the virus itself; ebola is survivable if caught early and treated with fluids even without the experimental treatments - Ebola is ironically preventable by measures no more sophisticated than those needed to avoid a common cold. Actually, the common cold (Rhinovirus) is more infectious than Ebola because it is capable of airborne transmission while Ebola is not.
Ebola poses a greater risk to the health care professionals in countries with advanced medical care than the general populace (another reason why I support travel restrictions; it's one thing for medical staff to sign up to treat Ebola in its source countries; it's quite another to expect them to treat travelers who fraudulently travel into their countries, potentially exposing some members of the general public and hospitals themselves to an infection source in the process).