To ensure better deposit of drugs in nasal cavity other than lung, nasal products such as nasal sprays generate particles with aerodynamic diameters mostly between 20-200μm. However, nasal sprays generate some (often <5%) particles <10μm, these tiny particles can penetrate the lower respiratory tract or lung. It is therefore important to quantify this fine particle dose (FPD) generated by nasal sprays. Cascade impactors (multi-stage cascade impactor, ACI) are used to capture 0-10μm particles. The combination of cascade impactor with nasal spray expansion chamber is used to measure fine particle doses of drugs in nasal sprays and nasal aerosols.