You have to understand the different mechanisms in place. Cloth mask is a woven fabric meant to trap particles of a specific size. Carbon absorption is used to trap organic particles which include smells. Hence you won't smell anything. It doesn't mean it specifically filters out by size.Not an expert, but I've heard on radio story ....one girl was telling that masks are useless as you can even smell that somebody farts... and they explained that this is because fart's particles are much smaller than Covid virus.. and in military gas mask you cannot smell anything
Here's the more relevant quote to point out that it may not be so useful for virus:Here we go
Given a global shortage of N95 respirator masks, Ottawa police will don their force-issued gas masks as protection should a call dictate officers could be exposed to the novel coronavirus, according to the deputy chief.ottawacitizen.com
Gas masks offer police protection from particulates and aerosols and are typically worn during mass demonstrations or riots.
Good for dealing with tear gas, probably not so much for virus.