An inhaler comprising: (a) an air inlet port; (b) an entry passage extending from the air inlet port to a contact chamber inlet port; (c) a contact chamber having (i) first and second opposed ends (44, 16), (ii) a sidewall extending between the first and second opposed ends (44, 16) that in cross section is curved, and (iii) a contact chamber outlet port positioned on the sidewall intermediate the inlet port and the second opposed end, the second opposed end having an opening in air flow communication with a dosage chamber, the contact chamber inlet port provided in the sidewall and facing a portion of the sidewall opposed to the contact chamber inlet port, wherein the inlet port is oriented so that the air entering the contact chamber instead of being directed towards the dosage chamber, is directed by the contact chamber inlet port to a portion of the sidewall of the contact chamber, the contact chamber having a cross sectional area that is greater than the cross sectional area of the entry passage; and, (d) an inhaler air outlet port positioned downstream of the contact chamber wherein: either the second opposed end does not have any wall portions, and so the second opposed end of the contact chamber comprises an open end, or alternatively the second opposed end has a wall portion having an opening which is at least the size of an opening into the dosage chamber. (a) an air inlet port; (b) an entry passage extending from the air inlet port to a contact chamber inlet port; (c) a contact chamber having (i) first and second opposed ends (44, 16), (ii) a sidewall extending between the first and second opposed ends (44, 16) that in cross section is curved, and (iii) a contact chamber outlet port positioned on the sidewall intermediate the inlet port and the second opposed end, the second opposed end having an opening in air flow communication with a dosage chamber, the contact chamber inlet port provided in the sidewall and facing a portion of the sidewall opposed to the contact chamber inlet port, wherein the inlet port is oriented so that the air entering the contact chamber instead of being directed towards the dosage chamber, is directed by the contact chamber inlet port to a portion of the sidewall of the contact chamber, the contact chamber having a cross sectional area that is greater than the cross sectional area of the entry passage; and, (i) first and second opposed ends (44, 16), (ii) a sidewall extending between the first and second opposed ends (44, 16) that in cross section is curved, and (iii) a contact chamber outlet port positioned on the sidewall intermediate the inlet port and the second opposed end, (d) an inhaler air outlet port positioned downstream of the contact chamber wherein: either the second opposed end does not have any wall portions, and so the second opposed end of the contact chamber comprises an open end, or alternatively the second opposed end has a wall portion having an opening which is at least the size of an opening into the dosage chamber. either the second opposed end does not have any wall portions, and so the second opposed end of the contact chamber comprises an open end, or alternatively the second opposed end has a wall portion having an opening which is at least the size of an opening into the dosage chamber.