Problem with filters is "what kind of filter is on the mask?" Masks issued to troops for training have simple mechanical (dust) filters effective to remove tear gas particles.
War filters are effective against chemical agents and have a finite life when opened.
My case is that the military discards (declares surplus) things that are broken and worn out, as well as some things that are new, never been opened, and are simply excess stock. I am not willing to take the chance with a surplus mask.
My team, sponsored and funded by the federal government, utilizes fresh off the shelf commercial equipment rather than military equipment.
Why take a chance with your life or safety.