Application of the BAW device as a gas sensor is achieved by placing a gas specific sensing film on the surface of the device. When the sensing film gets exposed to the target gas, mechanical perturbations in the sensing film will cause a corresponding change in the resonant frequency of the acoustic wave device.

Mechanical examples:

1. Mass loading as a concentration of gas adsorbs (sticks onto) onto the surface of the sensing film will result in a decrease in resonant frequency.
2. Changes in a sensing film as a concentration of gas diffuses into the bulk of the sensing film can result in elastic stiffening or softening. Elastic stiffening will result in an increase in the resonant frequency, while elastic softening will result in a decrease in resonant frequency.
3. Pressure exerted on a diaphragm that makes up the construction of the TSM device resulting in a shift in resonant frequency.
4. Stress or strain coupled into the resonator by the packaging resulting in an increase or decrease in oscillation frequency.