A deagglomerator for a breath-actuated dry powder inhaler comprising: an airflow adaptor (500)； an inner wall (512) defining a swirl chamber (514)； a dry powder supply port (522) in the first end (518) of the swirl chamber； at least one inlet port (524,525) in the inner wall of the swirl chamber adjacent to the first end of the swirl chamber providing fluid communication between a region exterior to the deagglomerator and the first end of the swirl chamber； an outlet port providing fluid communication between the second end (520) and the airflow adaptor (501)； and wherein the airflow adaptor comprises at least one swirl chamber by-pass port (502,503,504,505) for allowing air to flow from a proximal end of the airflow adaptor to a distal end of the airflow adaptor independently of the swirl-chamber when a breath-induced low pressure is applied to the distal end of the airflow adaptor.
