Clearing the Air: A Comprehensive Guide to Air Filtration Terminology

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Clearing the Air: A Comprehensive Guide to Air Filtration Terminology

You’ve probably encountered a variety of technical terms and jargon in the air filtration industry that can be overwhelming to decipher. That’s where our comprehensive guide to air filtration terminology comes in. Our index page provides clear and concise definitions of the most important air filtration terms you need to know. By familiarising yourself with these key concepts, you’ll be better equipped to make informed decisions about which air filtration system is right for your needs.

Air Filtration Terminology



Acronym for Air Handling Unit.

Activated Carbon Filter


Activated carbon filters are air filters that use activated carbon to remove pollutants and odours from the air.

Air Conditioning


Air conditioning is the process of regulating and maintaining the temperature, humidity, and air quality of an indoor space.

Air Filter

An air filter is a device that removes particles, contaminants, and pollutants from the air.

Air Handling Capacity

Air handling capacity refers to the amount of air that an air handling unit can circulate or move through a space in a given time, typically measured in Meters Cubed Per Hour (m3hr) or sometimes referred to as CMH.

Air Pressure

The air resistance created by a filter, measured in Pascals (Pa).

Air Purifier

An air purifier is a device that uses various technologies, such as HEPA filters and activated carbon filters to remove particles, contaminants, and pollutants from the air in a space.

Air Quality


Air quality refers to the degree to which the air in a space is free from pollutants, contaminants, and other substances that may be harmful to human health and the environment

Airborne Particles

Airborne particles are tiny particles that float in the air and can include dust, pollen, mould spores, bacteria, viruses, and other pollutants.


Allergens are substances, such as pollen, dust mites, pet dander, or certain foods, that can trigger an allergic reaction in some people by causing the immune system to overreact to otherwise harmless substances.


Asbestos is a group of naturally occurring minerals that were widely used in construction and manufacturing due to their heat-resistant and insulating properties, but can cause serious health problems if the fibres are inhaled.

Auto Emissions

Auto emissions are the gases and particles that are released from vehicles, such as cars, trucks, and buses, as a result of the combustion of fuel, and can contribute to air pollution and negative health effects.

Bag Filter

A bag filter is a type of air filtration system that uses a bag-shaped filter medium to capture particles, contaminants, and pollutants as they pass through the filter.


A biodegradable material is one that can be broken down naturally by microorganisms, such as bacteria or fungi, into simpler compounds and eventually decomposed back into the environment without causing harm.

Carbon Granules

Carbon granules are small particles of activated carbon that are used to adsorb or remove impurities, pollutants, and odours from the air.

Carbon Panel Filter

A carbon panel filter contains activated carbon to adsorb or remove impurities, pollutants, and odours from the air.

Clean Rooms

A clean room is a highly controlled and sterile environment that is used in medical and manufacturing settings to prevent contamination and maintain the quality of products by controlling the levels of airborne particles, humidity, temperature, and air pressure.

Compact Cassette Filter

A compact cassette filter is another name for a rigid bag filter.


A contaminant is a substance, particle, or agent that is present in a material or environment and can cause harm, pollution, or impurity.


Dander is tiny flakes of skin, hair, or feathers from animals, such as cats, dogs, or birds, that can cause allergic reactions in some people.

Dry Glass Panel Filter

A dry glass panel filter uses a fibreglass filter medium to capture particles, contaminants, and pollutants from the air as they pass through the filter, without the need for a wetting agent.

Dust Holding Capacity

Dust holding capacity is the maximum amount of dust or particles that an air filter can hold before needing to be replaced or cleaned.


EN779 is a European standard that specifies the testing and classification of air filters based on their efficiency and ability to capture particles of different sizes, and is commonly used in HVAC and air filtration applications.

Energy Efficiency

Energy efficiency refers to the use of technology and practices that reduce the amount of energy required to provide a certain level of service or output, resulting in less waste and lower energy costs.


The environment refers to natural and physical surroundings, including air, water and land.

Extractor Fan

An extractor fan is a ventilation device that is used to remove unwanted odours, moisture, heat, and pollutants from a room or enclosed space by extracting the air and expelling it outside.


A filter is a device or material that is designed to remove or trap particles, contaminants, or impurities as they pass through.

Filters Direct

Filters Direct is a leading UK supplier of HVAC filters, such as pleated panel filters, bag filters, HEPAs and wire frame fan coil filters.

Filter Grade

Filter grade refers to the level of efficiency or performance of an air filter in capturing and removing particles or contaminants of a certain size, as determined by industry standards.

Filter Media

Filter media refers to the material or substance that is used in an air filter to trap or remove particles, contaminants, or impurities from the air.

Final Pressure Drop

Final pressure drop refers to the maximum amount of resistance or pressure that an air filter can withstand before needing to be replaced or cleaned. It is determined by measuring the pressure difference between the clean and dirty air side of the filter.

Fume Extraction System

A fume extraction system is a device or system that captures and removes potentially harmful fumes, gases, or vapours from an industrial or laboratory environment to protect workers and maintain a safe working environment.

Glass Fibre Media

Glass fibre media is a type of filter media made from woven or non-woven glass fibres.

Grease Filter

Grease filters are commonly used in commercial kitchens and ventilation systems to trap grease and smoke particles produced during cooking. This prevents them from building up in ductwork or causing fire hazards.


HVAC stands for Heating, Ventilation, and Air Conditioning. It refers to the system used to control the temperature, humidity, and air quality of indoor spaces.

HEPA Filter

A HEPA filter, or High-Efficiency Particulate Air filter, is a type of air filter designed to capture and trap small particles and pollutants with a high level of efficiency, typically up to 99.97%.


HRV stands for Heat Recovery Ventilation. This is an energy-efficient ventilation system that recovers heat from outgoing stale air and transfers it to incoming fresh air.

Humidity Resistance

Humidity resistance refers to the ability of a material to withstand exposure to high levels of moisture or humidity without losing its performance or structural integrity.

Initial Pressure Drop

Initial Pressure Drop is the amount of resistance it takes for air to pass through a brand new filter.

ISO 16890

ISO 16890 is a standard for air filter testing and classification. Is it based on the particle size distribution of airborne particles in ambient air.

Maximum Working Temperature

Maximum working temperature refers to the highest temperature that an air filter can withstand without degrading or malfunctioning.

Moisture Resistance

Moisture resistance refers to a filters ability to withstand a damp environment without degrading or malfunctioning.

Multi Wedge HEPA

Multi-wedge HEPA refers to a type of HEPA filter with a design that increases the filter’s surface area and holding capacity, allowing for efficient air filtration.


MERV stands for Minimum Efficiency Reporting Value, which is an American rating system. It is used to measure the effectiveness of air filters in capturing and removing airborne particles of different sizes.

Metal Case HEPA Filter

A metal cased HEPA filter is a high-efficiency particulate air filter that has a sturdy metal casing surrounding the filter media to protect it from damage and provide structural support.

Metal Case Pleated Panel Filter

A metal case pleated panel filter is designed to remove dust and other airborne contaminants from HVAC systems. It has a rigid metal frame which provides support and durability.


A micron is a unit of measurement equal to one-millionth of a meter. It is commonly used to measure particle sizes in air filtration.


Microscopic refers to objects or organisms that are too small to be seen with the naked eye and require magnification to be visible.


MVHR stands for Mechanical Ventilation with Heat Recovery. This is an energy-efficient ventilation system that uses heat from outgoing stale air to warm incoming fresh air.

Natural Fibre

A natural fibre is a type of fibre that is obtained from plants or animals, such as cotton, wool, silk.

Oiled Glass Panel Filter

An oiled glass panel filter is made of glass fibre media and treated with oil. This increases its efficiency in capturing contaminants.

Paper Pleats

Paper pleats are a type of filter media made from pleated paper sheets that are commonly used in air filtration.


Particles are small pieces of matter that can vary in size, shape, and composition.

Pleated Panel Filter

Pleated panel filters are made from a sheet of filter media that has been folded into pleats. This increases the surface area available for trapping airborne particles.


Pollen is a fine powdery substance produced by plants that is transported by the wind or by insects.


Pollutants are substances, particles, or gases that are released into the environment. These can cause harm to living organisms or damage the natural environment.


Pollution refers to the presence or introduction of harmful substances or contaminants into the natural environment. This can have detrimental effects on human health, wildlife, and the ecosystem.


Polyester is a synthetic polymer made from a type of plastic.


PIV stands for Positive Input Ventilation. This is a ventilation system that supplies fresh air into a building while simultaneously pushing out stale air.


PVC stands for polyvinyl chloride, which is a synthetic plastic polymer.

Replacement Filter

Replacement filters replace the existing filters after they have become clogged or reached the end of their life.

Rigid Bag Filter

Rigid bag filters are a type of air filter that use a bag-shaped media supported by a rigid metal frame. They are commonly used in commercial and industrial HVAC systems for their high dust-holding capacity and low resistance to airflow.

Synthetic Fibre

Synthetic fibres are man-made fibres that are produced by combining different chemicals and materials.

Synthetic Media Roll

A synthetic media roll is a long sheet of material made from synthetic fibres. It is used to capture and remove airborne particles and pollutants.

Thermal Stability

Thermal stability refers to the ability of withstanding high temperatures without degrading or losing its filtering efficiency.


Velocity refers to the speed at which air moves through a given space.


Ventilation refers to the process of bringing fresh air into an indoor space and removing stale or polluted air.


VOCs (volatile organic compounds) are chemicals that can be emitted as gases from certain solids or liquids. They can have negative effects on air quality and human health.

Washable Pleated Panel Filter

A washable pleated panel filter can be cleaned and reused multiple times to capture and remove airborne contaminants.

Wood Case HEPA Filter

A wood cased HEPA filter is a high-efficiency particulate filter that has a wooden frame casing surrounding the filter media. It protects the filter from damage and provides structural support.

Wire Frame Fan Coil Filter

A wire frame fan coil filter is typically used in HVAC systems. They consist of a wire frame and a filter media, which captures particles and contaminants from the air.

Wire Frame Filter

A wire frame filter uses a wire mesh to support the filter media and maintain its shape.

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