Abstract: Apparatus and methods for delivery of air-borne materials from pulsatile delivery devices by passing the emissions from such devices and air in a coaxial manner through a suitable mixing chamber. Preferred apparatus include a chamber defining an axis of air flow, a plurality of pulsatile delivery devices, an actuator in communication with the devices for selective actuation thereof, and a device for introducing air at a first end of the chamber and for flowing that air substantially along the axis. The pulsatile delivery devices are positioned at the first end of the chamber such that actuation of the devices emits an air-borne substance substantially along the axis of air flow.

Abstract: A virtual impactor having improved efficiency and low wall losses in which a core of clean air is inserted into the aerosol flow while aerosol flow is maintained adjacent inner wall surfaces of the focusing portion of the impactor. The flow rate of the core and the length of the throat of the impactor's collection probe, as well as the dimensional relationships of other components of the impactor adjacent the separation region of the impactor, are selected to optimize separation efficiency.

Abstract: A parallel flow diffusion battery for determining the mass distribution of an aerosol has a plurality of diffusion cells mounted in parallel to an aerosol stream, each diffusion cell including a stack of mesh wire screens of different density.