An aerosol medication delivery apparatus (910) for use with a pMDI canister having medication and a propellant contained therein under pressure, wherein the pMDI canister has a discharge orifice from which the medication and propellant can be discharged forming an aerosol, the apparatus comprising: a chamber housing (924) having an input end (946) and an output end (948) and defining an interior space (939), wherein the input end receives the medication discharged from the discharge orifice of the pMDI canister into the interior space and wherein the medication can be withdrawn from the interior space by inhalation by a patient from the output end a mouthpiece (955) operatively attached to the output end and a valve (960) located near the output end comprising a valve seat (964) having a sealing surface (966) and a valve member (962) comprising an inner portion and an outer portion (965), the inner portion (963) having a central open area (961) and a sealing portion (967) at the perimeter of the central open area that mates with the sealing surface when the valve is closed, wherein the inner portion allows medication to be withdrawn through the central open area but prevents backflow into the chamber housing and the outer portion located in a peripheral opening defined between the chamber housing and the mouthpiece, the outer portion operative to prevent air flow through the peripheral opening upon patient inhalation but which permits air flow through the peripheral opening upon exhalation into the mouthpiece.
