These brand new U.S. Safety half mask supplied air respirators are ideal for use in almost any environment where continuous use of a respirator mask is desirable. Of course, you should consult your resident expert for your specific requirements! By using a positive air flow from an outside source you increase the safety margin and eliminate the cost of expensive replacement cartridges, which sometimes must be replaced daily (Read $$$ - for you bean counters!) in atmospheres with a high quantity of airborne particulate matter. These masks are factory new in the box. There are no filters to deteriorate. So, they are as good the day they were made.