The air-to-cloth ratio is the volumetric flow rate of air (m<sup>3</sup>/minute; SI m<sup>3</sup>/second) flowing through a dust collector's inlet duct divided by the total cloth area (m<sup>2</sup>) in the filters. The result is expressed in units of velocity.
The air-to-cloth ratio is typically between 1.5 and 3.5 metres per minute, mainly depending on the concentration of dust loading.