Intervention
Mechanical ventilation
Part of: Ventilation
Also: mechanical ventilation system, forced ventilation, balanced ventilation, mechanical extract ventilation, heat recovery ventilation
Supplying or extracting air with a fan rather than relying on wind and temperature difference. Because the flow is driven, it can be sized, filtered, balanced and measured — and it stops when the fan stops or when an occupant switches it off.
What it is
The difference from natural ventilation is not the amount of air but the control over it. A fan delivers a flow that does not depend on the weather or on whether anyone opens a window, and a designed system can therefore be given a rate per person or per room and hold it.
Three further things become possible once air is driven. It can be filtered on the way in, which matters when outdoor air is the problem. It can be balanced, so that supply and extract match and the building is neither pressurised nor depressurised — a depressurised house draws in soil gas, which is how a ventilation change can raise radon. And heat can be recovered from the air leaving, which is what makes high air exchange affordable in a cold climate.
What it cannot survive is neglect: an unmaintained, unbalanced or silenced system ventilates on paper only.
What the studies report
| Linked to | Effect | Population | Study design | Source | Checked |
|---|---|---|---|---|---|
| Carbon dioxide (CO₂) | difference 491 | — · classroom | ventilation intervention study in classrooms: mechanical ventilation set to a carbon dioxide threshold in twelve classrooms and the measured concentrations compared with the baseline week | F-1651 A ventilation intervention study in classrooms to improve in… (2013) | machine |
| Carbon dioxide (CO₂) | mean 841 | — · classroom | ventilation intervention study in classrooms: mechanical ventilation set to a carbon dioxide threshold in twelve classrooms and the measured concentrations compared with the baseline week | F-1652 A ventilation intervention study in classrooms to improve in… (2013) | machine |
| Carbon dioxide (CO₂) | difference 70 | — · hospital treatment room | controlled burning tests of moxa wool in a hospital treatment room in Taiwan: emissions of CO2, CO, formaldehyde, TVOC, PM2.5 and PM10 measured without control, with local exhaust ventilation and with an air cleaner | F-0306 Lu et al. Controlling Indoor Air Pollution from Moxibustion (2016) | machine |
| Carbon monoxide (CO) | difference 91 | — · hospital treatment room | controlled burning tests of moxa wool in a hospital treatment room in Taiwan: emissions of CO2, CO, formaldehyde, TVOC, PM2.5 and PM10 measured without control, with local exhaust ventilation and with an air cleaner | F-0307 Lu et al. Controlling Indoor Air Pollution from Moxibustion (2016) | machine |
| Formaldehyde (CH₂O) | difference 79 | — · hospital treatment room | controlled burning tests of moxa wool in a hospital treatment room in Taiwan: emissions of CO2, CO, formaldehyde, TVOC, PM2.5 and PM10 measured without control, with local exhaust ventilation and with an air cleaner | F-0308 Lu et al. Controlling Indoor Air Pollution from Moxibustion (2016) | machine |
| Total volatile organic compounds (TVOC) | difference 41 | — · hospital treatment room | controlled burning tests of moxa wool in a hospital treatment room in Taiwan: emissions of CO2, CO, formaldehyde, TVOC, PM2.5 and PM10 measured without control, with local exhaust ventilation and with an air cleaner | F-0309 Lu et al. Controlling Indoor Air Pollution from Moxibustion (2016) | machine |
| Carbon dioxide (CO₂) | the authors state that the difference cannot be confirmed statistically because only 9 spaces were mechanically ventilated | school pupils and kindergarten children · classroom and kindergarten playroom | measurements of CO2, air temperature and relative humidity during occupancy in 311 classrooms and playrooms of schools and kindergartens throughout Slovenia before energy-efficiency renovation and before the COVID-19 pandemic (302 naturally and 9 mechanically ventilated spaces), with a comparison of measured averages against a COVID-19 airborne transmission model | F-0406 Measurements of air quality in kindergartens and schools in … (2022) | machine |
| Mould | prevalence 18 | households in energy-efficient dwellings · dwelling | survey and sampling of 149 energy-efficient dwellings in Switzerland (44 recent, 105 retrofitted; natural or mechanical ventilation): occupant questionnaire on visible mould, surface samples cultured for actively growing fungi, bedroom settled dust | F-0544 Fungal Contaminants in Energy Efficient Dwellings Impact of … (2020) | machine |
| Radon | difference 83 | unoccupied test flat · apartment | 22 ventilation experiments over one year in an unoccupied flat in a former uranium mining region in Germany: a decentralised ventilation system with different modes and fan performance levels, indoor radon monitored in living room, bedroom, kitchen, corridor and bathroom with meteorological parameters | F-0627 Decentralised ventilation efficiency for indoor radon reduct… (2022) | machine |
| Carbon dioxide (CO₂) | mean 811 | — | chamber and room study of the combined use of air conditioners, air purifiers and a fresh air system: indoor carbon dioxide, particles and thermal parameters measured under single and joint operating conditions | F-1026 Jia et al. Synergistic Impact on Indoor Air Quality: The Combined Use o… | machine |
| Carbon dioxide (CO₂) | other 790 | preschool children · kindergarten classroom | measurement and modelling study in a kindergarten in Korea: carbon dioxide and PM2.5 logged in two classrooms through the daily programme, with mechanical ventilation and window opening recorded and the required airflow calculated | F-1032 Lee et al. Strategies for Effective Management of Indoor Air Quality in… (2023) | machine |
Each row is one Finding — a sentence as printed in one study, recorded with its page in the Coridum Knowledge Base. Follow the Finding number for the exact wording and the citation. Checked says who verified the row: machine means every automatic check passed and the surrounding text was read; person means someone read the sentence in the document. Rows are re-checked by a person over time. The studies are curated in the Coridum Knowledge Base; the reading of them together is a Claim, shown separately.
Cite this page
Coridum Research. Mechanical ventilation. Coridum Knowledge G-0126, 16 September 2026. https://coridum.com/k/G-0126/