Implementations described and claimed herein provide systems and methods for sampling particles from air. In one implementation, an inlet opening is defined in a proximal end of a cassette top, and the inlet opening has an inlet diameter. An internal surface extends along an airflow curve from the inlet opening to an internal cavity. A sampling substrate is formed by at least one grid attached to a filter. The sampling substrate is disposed in the internal cavity at an internal distance from the inlet opening. The inlet opening and the airflow curve of the internal surface generate an airflow of the air to the sampling substrate. The sampling substrate collects a set of the particles from the air, and the inlet diameter, the airflow, and the internal distance dictate a cutoff diameter of the set of particles collected from the air by the sampling substrate.