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Glossary of Terms

Like any other specialist industry, ventilation has has its own unique set of terminology, definitions, and abbreviations. This essential glossary to ventilation compiles the most common terms you are likely to hear and will definitely need to know if you are looking to understand ventilation in more detail.

A - B - C - D - E -F - G - H -I - J -K -L -M - N -O -P -Q -R -S -T -U -V -W -X -Y -Z


Airflow Rates: Measurement of a flow of air through a ventilation unit or duct.
Air Changes per Hour (ACH): Air changes in relation to the volume of a room.
Axial Fan: The design of fan impeller or blades used to move air.
Acoustics: Noise.
Air leakage: The rate at which air leaks form a building.
Air Permeability: The measurement of air leakage (ie (>) 5m³/(h.m²) at 50 Pa).
Approved Document: Building regulation document - Approved Document F relates to Ventilation.



Balanced System: Supply and Extract airflows match.
Building Regulations: A minimum standard for design, construction and alteration of buildings.
Boost: High speed fan mode.
Background Ventilation: A small ventilation opening designed to provide controllable whole building ventilation.
Background Ventilator:Trickle vent



Condensation: The point at which air releases moisture.
Centrifugal Fan:Type of impeller designed to cope with high pressures.
A way of checking an installation and measuring airflows of a system.
Combustion appliances: Appliances that utilise combustion fuels such as gas or oil
CO2: Carbon Dioxide - colourless odorless gas.


Damp: An indication/problem with a building fabric.
Dew Point: The point at which water is released by air.
Dwelling: A residence or place to live.
DVCG: Domestic Ventilation Compliance Guide - Guidance on the installation of ventilation systems.
Dust mites: Microscopic mites found in household dust.


Extractor Fan: A unit designed to expel moist stale air from a room.
Equivalent area: The aerodynamic measurement of an opening.
EST: Energy Saving Trust
ERP: Energy Related Products - European energy efficiency ratings.


Fire stopping: A way of utilising products to prevent the spread of fire.
Filter: Used in some units to filter particle matter from the air.
Free area: Calculation of an open area of a ventilator or grill.
FAI: Fresh: Air intake - much like a trickle vent.


Grill: A vent used to aid air to or from a dwelling or room.



Humidity: Amount of moisture in the air.






Litres per Second: A measurement of air movement.
Live: The positive side of an electrical circuit.
Line: The positive side of an electrical circuit.
Live switch: A live line that can be turned on or off from a control or switch.



MVHR: Mechanical Ventilation with Heat Recovery - An energy efficient ventilation unit designed to recover wasted energy.
Mechanical Extract Ventilation - A continuous running ventilation system.
Mould: A type of fungus that thrives in damp areas.



Noise Rating or NR: A measurement of noise.
NRVU: Non Residential Ventilation Unit.




Passive Stack: A type of ventilation that has no mechanical assistance and relies on atmospheric conditions.
Positive Input Ventilation: A ventilation system that pushes air into a property to reduce humidity and contaminants.
Purge Ventilation: Facility to change air within a room at a rapid rate (i.e. open a window).




Resistance: Friction caused by ancillaries and components used in ventilation.
Radon: A harmful gas formed underground in rock.
RVU: Residential Ventilation Unit.



SAP: Standard Assessment Procedure, a software that regulates building efficiency.
SFP: Specific Fan Power, measured in watts per litre moved per second. 
System: Type of ventilation unit.
Switch Live: A live line that is controlled by a switch or sensor.




Trickle Vents: Background ventilators - normally fitted in windows.
Trickle: A low extract rate - normally known as whole dwelling ventilation rate.



Unit: A ventilation component consisting of electronic and a fan.



Ventilation: Replacement of moist stale air with fresh air.
Volt Free: A cable or contact with no voltage.
VOC: Volatile Organic compounds - colourless and odorless gas released from various household products.
Velocity: Speed of air through a duct or ventilation unit.



Whole dwelling Ventilation: The continual ventilation rate within a dwelling.
Whole dwelling extract Ventilation: A higher extraction rate of air to remove humid stale air.
Wireless: Radio controlled operation of boost or fan speed.




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