The valve

Not sure what you mean by "breathing" mask.. but the different types of O2 masks are:

* Non re-breather (same as partial re-breather) -- has a reservoir bag as well as flaps over the holes on the side of the mask -- allows for close to 100% O2 delivery

* Simple face mask -- no reservoir it's just a mask that goes over the mouth and nose -- allows for approx 40-50% O2 delivery

* Venturi mask - has either a dial indicating O2 concentration or colored attachable vents that snap on allowing for specific O2 concentration.

Thx for reply :)

Btw, I refer the non breathing n breathing mask frm this:

http://www.ehow.com/facts_6084936_rebreather-vs_-non_rebreather-mask.html

I juz unsure the difference of the valve frm them n wanna know how do they look like into the mask system