hi there kumanosuke
for your info, i wouldn't recommend wearing a (or this) gas mask for paint ball purposes.

although i have never played paint ball before, from what i understand - the purpose of the (paintball) mask is designed to provide protection
in the event if you are shot in the face. in addition to that, the mask has 'open vents' for ease of breathing when you are running around.

this gas mask (like any other gas mask) is designed for breathing protection. i have used this one before and:-
1) the there is fair bit of breathing resistance when you are breathing (you might end up fainting or gasping for air when running around )
2) the separate eye piece lens results in limited forward and side vision;
3) its quite 'heavy' with the filter attached (that creates the breathing resistance as noted in (1));
4) i recall they do come in sizes so a proper fitting one is recommended or your face is going to hurt!
5) there isn't a 'frame' designed around the mask, so it kinds of fit to your face and if something hits you when you are wearing it, its going to hurt.
6) think the lens may not be of strong quality plastic type of things that can withstand a direct hit from a paintball..
7) maintenance wise, its just the filter cos after opening it, there is a shelf life based on how and what you use it for. the mask itself is made
from latex(?) so all it needs is a good wiping. i think the lens, the straps and the inner nose piece can be removed too for cleaning purposes.

again, i am not an expert on the mask itself, just sharing what i recall of it. as a novelty item, sure - get the gasmask... it makes a good party
story as they say...

hope above helps... cheers! ct