Will the Belgian Gas Mask cause lung problems like the Russian Soviet GP-5?

Question

and will it protect agenst smoke bombs, tear gas, and other minor chemicals?

Answer 1

Again you fail to mention if the gas mask in question is second-hand?

All filters have a shelf-life, if they have had the rubber seal removed and fitted to the Gas-mask there is no telling how good they are or if they have been subject to contamination.

Unless you can obtain a new mask complete with unused filter you cannot be sure they will perform satisfactorily.