Air Purifiers and Air Cleaners – Glossary of Terms

Air Cleaners glossary

Throughout these pages, you may come across phrases that you are unfamiliar with so we have put together this handy air purifier and air cleaner glossary of terms. If you have any questions or would like to speak to one of the air cleaner team, please call 044 (0)1706 238000 or email:

Fine liquid or solid particles suspended in air. For example Fog or Smoke. They can be microscopic and less than 1 micron in size. They can chemical or biological and composed of many parts.

Air Change Rate
The number of times per hour the room air volume will pass through the air cleaner or air purifier. A typical air change rate for a well selected HEPA system would be about 5 Air Changes per hour. ACR can be calculated by dividing the Air Volume Flow Rate M3/hr of the air cleaning unit by the volume of the room in M3.

Air Cleaner
The Camfil air cleaner typically uses HEPA class filtration to remove ultra-fine airborne particles from the air in a room that may be bacteria or virus and cause infection or chemically toxic when inhaled. It would be used in industrial applications. Camfil 2000 and 6000 models are of this type.

Air Image
Computer presentation software that enables real time display of particle counter results demonstrating air cleaning performance of Camfil air purifiers.

Air Purifier
The Camfil air purifier uses typically uses HEPA class filtration to remove ultra-fine airborne particles from the air in a room but also has molecular filtration to remove odours and selected noxious gases and fully clean the air. It would be used in office, light industrial and residential applications. Camfil City M 300 and 800 Models are of this type.

Air Volume Flow Rate
The Air Volume Flow Rate for an Air Cleaner is usually given in Metres3/Hour although Cubic Feet per minute CFM is sometimes used for older unit measurements or units manufactured in the USA.

Airborne contaminant that can induce an extreme reaction in a person who has an allergy to that substance. Typical Allergens are pollen, animal hair, skin particles and bed-mites and can be inhaled or just have skin contact. Anti-Histamines are the usual medication.

Air Quality Index
An index published usually on a daily basis to advise on how much airborne pollution is being monitored and what effect this will have on public health. Commonly experienced outdoor problem pollutants are PM2.5 fine combustion particulates, Nitrogen oxides (NOx), Ozone and Sulphur oxides (SOx).
Others that may be experienced are Volatile Organic Compounds VOC’s. Carbon monoxide. The Clean Air Act and WHO guidelines give information on concentration limits for each pollutant.

American Society of Heating, Refrigeration and Air Conditioning Engineers who produce comprehensive guidance on air cleaning plant.

A respiratory complaint that can be serious in young and older people and is the result of allergens sometimes airborne causing irritation and swelling in the respiratory system. In extreme cases it can lead to increased chance of mortality.

Single-celled organisms that quickly multiply through cell division. Harmful bacteria called pathogens can cause disease, others can be beneficial to humans, animals and plants.

CityCheck IAQ Kit and Report – Camfil
An easy-to-use inexpensive Kit that has sensors to measure and quickly produce a fully detailed report on 39 different indoor sourced airborne contaminants. These are Aldehydes and Volatile Organic Compounds frequently given off from new paints, carpets and furnishings.

Chartered Institute of Building Service Engineers(CIBSE)
UK Body that produces Guidance on Air Quality and Indoor Air Quality issues

Concentration (Airborne Particles)
Measured in number of particles per cubic Metre of air. For smaller particles of 0.3 to 0.5 micron diameter concentration may vary from less than 1 million per M3 to 1000 million (1billion) in parts of the underground system in central London. A thousand times variation is surprising when the particles are invisible to the unaided human eye.

Droplet nuclei
Airborne particles of about 1 to 4 microns that are the residue after evaporation of expelled droplets. They can carry airborne infection that can be transmitted if they land on eyes or are inhaled by a non-infected person or animal.

Electrostatic Precipitator
An air cleaning device that uses an electrical charge to attract airborne dust out of the airstream onto plates. High maintenance, energy and running costs, safety issues and unwanted ozone are reasons why this type of air cleaning device is best avoided.

Energy Efficiency
Minimum use of energy to produce the required clean air is very important. Camfil Air purifiers and air cleaners are outstanding in this regard. Typically they use less energy than some light bulbs and they can save energy by supplementing or even replacing some existing ventilation systems.

The Environmental Protection Agency is responsible in the USA for the regulation and prevention of polluting hazardous wastes, toxic chemicals in both air and water.

Flexible System Solutions
These Camfil Air purifiers and cleaners can be used in conjunction with control systems to minimise energy use as part of a overall building IAQ and energy efficiency strategy.

Particulate Air Filter
An air cleaning device that permits air to pass through but stops airborne particles.

Molecular Filter
An air cleaning device that permits air to pass through but stops molecular contaminants and certain contaminant gases.

HEPA Filter
High Efficiency Particulate Air filter. HEPA filters are made from pleated paper, usually fibreglass. In Europe HEPA filter classification is given by EN1822:2009 the test standard used by filter manufacturers. E10 to U17. The filter is tested to Most Penetrating MPPS

Is a biological substance produced as part of an allergic reaction that can cause swelling of body parts and restricted airways. It causes irritation, eye watering and running nose. Hay fever is a common manifestation of histamine in action.

Indoor Sourced Air Pollution
People are a main source of larger bio-particles and gas odours. There are also aerosols and VOC’s off-gassing from many materials and products used by people in buildings. A City Check test kit can be used to determine a wide range of indoor sourced molecular contaminants.

Indoor Air Quality (IAQ)
The IAQ inside a building can be tested and determined by comparison of key values such as temperature, humidity and airborne contaminants and gases with levels in standards and guidelines from International bodies such as ISO and the World Health Organisation.

Mechanical Air Filtration
The most effective method of air filtration used by Camfil that involves physical removal of the airborne particles from the cleaned airstream. Other methods such as ultra violet light radiation do not remove particles and these can cause subsequent dust deposits with the problems that entails.

A micron is one thousandth of a millimetre and is used to measure the size of dust. Particles below 10 microns in diameter cannot  be seen unaided by the human eye. A human hair is about 50 microns in diameter.

Most Penetrating Particle Size MPPS
The particle size that penetrates a filter medium at minimum particle stopping efficiency.

Negative Ions
Charged molecules that are found in certain environments and are sometimes attributed to a feeling of stimulation when inhaled. However they are also produced by Ozone and this can be unhealthy.

Ozone is a form of oxygen often produced by ultra violet light radiation and is highly unstable and reactive. It can be unhealthy when inhaled and so sources that produce Ozone are best avoided.

The production of gases from the chemical aging of a material over time. Commonly measured contaminants are Aldehydes and VOC’s. See VOC’s Below.

Particle Counter
Instrument used to count numbers of airborne particles in and give a concentration. Some instruments are capable of measuring a range of particle sizes and thereby give a distribution profile at a given time.

An organism that has the ability to cause infection and disease that can in the extreme cases be fatal.

PM 2.5
In air cleaning using filtration PM2.5 can be regarded as airborne Particulate Matter 2.5 microns and below in size. In city areas with traffic it mainly comprises fine combustion particulate that is extremely damaging to health when inhaled.

Sick Building Syndrome
A condition frequently attributed to buildings and is due to build up of indoor sourced air pollutants and poor ventilation. Air purifiers can be used to tackle these problems economically at point of need.

A reproductive form of microorganism that remains dormant until it finds the right environmental conditions of warmth, moisture and a food source to activate.

Ultra Violet light (UVC)
Ultra Violet light can be used to sterilise deposited bio-particles on surfaces and biofilms but cannot remove airborne particles from a moving airstream.
The energy required to irradiate and sterilize particles in a moving building ventilation airstream makes this technology currently uneconomic and therefore ineffective to use for this purpose.

An infectious organism that exists as a microscopic particle until it finds a host cell

Volatile Organic Compounds (VOCs)
These are volatile compounds that offgass from many materials and products used in homes and at work. Cleaning fluids, paints, floor and wall covering products give off VOC’s. They can trigger irritations to eyes, headaches and reactions. Sensitive people can become even more sensitized with exposure.

World Health Organisation
Worldwide Health Body that gives a true international view on health issues that is usually less biased than some national bodies.

Useful references include:



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