Air-to-cloth ratio

Also known as the air-to-media ratio, the air-to-cloth ratio indicates the amount of air that passes through a square foot of filter media.


Actual cubic feet of gas per minute: It refers to the amount of gas that flows per minute at a given temperature, pressure, moisture level, and composition, and is measured in terms of its true cubic feet per minute.

Blast Gate

A Blast Gate is a device utilized in the dust collection field that controls the movement of air and dust in a dust collection system.

Brake Horsepower

Brake horsepower (BHP) refers to the amount of power that the motor or fan generates in order to move air and collect dust from a particular area.


A dust collector blower is a mechanical device that creates a flow of air to transport dust and other particulate matter from one location to another.


A blockage of material that occurs at an opening, such as a hopper outlet or between bags.


CFM is an abbreviation for cubic feet per minute, and it refers to the amount of air that a dust collector can move in one minute.

Capture Velocity

The lowest air velocity needed to capture and contain dust particles produced by a source and transfer them into the collector.

Can Velocity

The faster the air rises through the system, the higher the can velocity. Air rises through the system more quickly the higher the can velocity.

Cold Spot

An area on an insulated baghouse where a constant metallic circuit passes through the insulation, resulting in an area without insulation.

Dust Collector

A cleaning device used to filter heavy dust particles from the air flowing through exhaust systems before discharging. It usually collects within a range of 0.003 grains per cubic foot.

Dust Loading

Dust quantity in the gas stream. Usually measured as grains of dust per cubic foot of air.

Diaphragm Valve

A valve operated via compressed air used to pulse bags.

Ductwork Drop

Used to describe the branch of the duct that descends from the primary line to the dust collection port.


Short for Environmental Protection Agency, the federal regulatory body that oversees the enforcement of health and safety standards in the US.

Entry Loss

It is the reduction of pressure resulting from the air flowing into a duct or hood.

Exhaust Volume

The quantity of air released by the fume hood. Also refers to the air quantity required to maintain a desired face velocity. Expressed in cubic feet per minute (CFM).

Filter Media

The material on the air filter that’s responsible for screening out airborne particulates. It is made of dense and fibrous materials that can have a non-stick coating that helps in releasing dust during the cleaning process.


Short for “Feet per Minute,” it is the imperial measurement used to determine the air velocity and the particles contained within. Different particle types require specific velocities for safe conveyance of airborne particles.


A fabric made by interlocking fibers without spinning, weaving, or knitting.

Filter Media

A permeable membrane in the filtration process used to separate particles in the fluid stream.


Small solid particles that form due to the condensation of solid material vapors.


Refers to the amount of processed gas going through the fabric filter dust collector divided by the cloth area filter itself. Gas flow is measured in CFM, while the cloth is per square feet.


A form of matter that uniformly occupies the given space at normal temperatures and pressure.


The process of using high pressure to press the filter medium at high temperatures. It is used to fuse the surface fiber to the filter medium’s body.


The weight used in air pollution control, equal to 1/7000 lb.

Gravity, Specific

Refers to the mass ratio of a substance’s unit volume comparable to the mass volume of a standard substance at a standard temperature.


Made from ultra-fine glass fibers, this filter media type that can capture at least 99.97% of particles with a working diameter equal or greater than 0.3 microns.


Refers to the static pressure of a dust collector that’s higher than average.

Hydrophobic Fibers

A type of fiber that won’t easily absorb water or other liquids.

Hydrophilic Fibers

A fiber variant that takes in water with relative ease.


The openings found between woven or felted filter bag fibers.

Inch of Water

The computation of the unit of pressure equal to the pressure released by a column of water that’s an inch high at a standard temperature.


Part of the ASHRAE rating, the Minimum Efficiency Reporting Values measure the filter’s particle capture capacity between 0.3 and 10 microns. The higher a filter ranks, the more efficient it is in capturing particles.

Micron (µm)

An abbreviation for the term “micrometer” or a millionth of a meter.


Similar to MERV, the Most Penetrating Particle Size measures the filter’s filtration efficiency for particles ranging from 0.12 to 0.2 microns.


A pressure-checking instrument.

Minimum Design Duct Velocity

The minimum air velocity needed to move the particulates in the air stream, measured in fpm.


Small material droplets caused by a change in temperature and pressure.


Short for National Electrical Manufacturers Association, the organization responsible for establishing technical standards for electrical equipment, like cords, plugs, starters, and others.


Short for National Fire Protection Association, this a US-based non-profit organization that publishes building and fire safety codes.


The Occupational Safety and Health Administration sets and enforces standards that guarantee safe and healthy working conditions in US-based facilities.


Polytetrafluoroethylene is a synthetic material that has a low friction coefficiency, leading to other materials not sticking to it.


A pressure equalizing chamber.

Pressure Drop

Refers to the pressure differential across the cloth, baghouse, or the entire system.

Pulse Cycle

The time interval between rows of bags pulsing within the same rows.

Pulse Interval

The time difference between pulsing a row of bags to the next row.

Pulse Jet

A generic term for pulsing collectors.


The redepositing of dust on the filter surface after pulsing, usually caused by turbulence within the hopper or dirty air plenum.

Reverse-Air Baghouse

A machine that uses reverse flow flushing for removing dust from the bags.

Shaker Baghouse

A machine that cleans the bags through constant and vigorous shaking.

Slot Velocity

The linear flow rate of contaminated air through the filter cloth, measured in feet per minute (fpm).

Variable Air Volume (VAV)

A type of fume hood exhaust system that maintains velocity through blower motor speed adjustment or balancing dampers based on changes in the position of the sash.


Measured in feet per minute or FPM, it refers to the speed of air.

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