Gas mask filters

my company (xxxxxxxxx) planning to purchase a gas mask filters. as we are chemical factory, regarding this we need filters which will work against: cyanide acid, ammonia and nitrous gases.
generally, we would like to purchase combined filter, which is valid for all this gas. but other possibility is also considered.
please, give us information what a possibility do you have regarding our demand (first time we need a technique character of a filter and price list).
would be nice if you help