Filtration Velocity: Air-To-Cloth Ratio

The terms filtration velocity and air-to-cloth (A/C) ratio can be used interchangeably. The formula
used to express filtration velocity is:

The air-to-cloth ratio (also called the gas-to-cloth ratio) is defined as the ratio of gas filtered
in cubic feet per minute (cfm) to the area of filtering media in square feet. Typical units used to
express the A/C ratio are:

These A/C ratio units reduce to velocity units. The units for filtration velocity are ft/min or
cm/sec.
The term gross air-to-cloth ratio refers to the total amount of cloth area used to filter the
entire flue gas stream. The term net air-to-cloth ratio is used to describe the net amount of
cloth available for filtering when one baghouse compartment is taken off-line for maintenance
or bag cleaning. The term net, net air-to-cloth ratio describes the amount of cloth available
when 2 compartments are taken off-line.