Tapered element oscillating microbalance
A tapered element oscillating microbalance (TEOM) is an instrument used for real-time detection of aerosol particles by measuring their mass concentration. It makes use of a small vibrating glass tube whose oscillation frequency changes when aerosol particles are deposited on it increasing its inertia.
Source: Wikipedia — Tapered element oscillating microbalance (CC BY-SA 4.0)