Intervention
Ventilation
Also: natural ventilation, mechanical ventilation, fresh air supply
Replacing indoor air with outdoor air, by opening windows (natural ventilation) or by fans and ducts (mechanical ventilation). It is the single most effective measure against the pollutants people and buildings emit, and carbon dioxide is its indicator.
Why it matters indoors
Every indoor source raises concentrations in proportion to how slowly air is replaced. Ventilation dilutes and removes what is emitted — CO₂, moisture, volatile compounds, odours, infectious aerosols — at the cost of energy and, near busy roads or on high-pollution days, of bringing outdoor particles in. The rate is expressed as air changes per hour or litres per second per person; standards such as ASHRAE 62.1 and EN 16798-1 set minimum rates per occupant.
Natural versus mechanical
Natural ventilation depends on window opening, wind and temperature difference, and is effective in bursts (cross-ventilation at breaks) but uncontrolled. Mechanical ventilation delivers a set rate continuously and can filter incoming air and recover heat, but must be commissioned and maintained — a mechanical system delivering half its design rate is the commonest finding in school and office audits.
What the studies report
12 of 20 Findings — those with the strongest study design.
| Linked to | Effect | Population | Study design | Source | Checked |
|---|---|---|---|---|---|
| Carbon dioxide (CO₂) | maximum level recorded as measure other; the value after is printed as a range and sits in extra | university students and staff (outbreak contacts) · university classroom | outbreak investigation with a contact cohort: 27 tuberculosis cases and 1665 contacts in underventilated university buildings in Taiwan, indoor CO2 measured before and after ventilation engineering, incidence of TB among contacts analysed with adjustment for contact investigation and latent TB infection treatment | F-0443 Effect of ventilation improvement during a tuberculosis outb… (2020) | machine |
| Carbon dioxide (CO₂) | other 97 (50–99.9) | university students and staff (outbreak contacts) · university classroom | outbreak investigation with a contact cohort: 27 tuberculosis cases and 1665 contacts in underventilated university buildings in Taiwan, indoor CO2 measured before and after ventilation engineering, incidence of TB among contacts analysed with adjustment for contact investigation and latent TB infection treatment | F-0444 Effect of ventilation improvement during a tuberculosis outb… (2020) | machine |
| Carbon dioxide (CO₂) | median 82 | geriatric inpatients and staff · hospital patient room | randomized, sham-controlled, crossover, open-label trial (February to May 2021): CO2 monitors placed in twelve double-bed patient rooms across two geriatric wards of a Belgian hospital, staff instructed to open windows, increase air exchange and reduce crowding to keep CO2 at or below 800 ppm; primary outcome time per day above 800 ppm | F-0475 Laurent Monitors to improve indoor air carbon dioxide concentrations… (2022) | machine |
| Carbon dioxide (CO₂) | median 78 | geriatric inpatients and staff · hospital patient room | randomized, sham-controlled, crossover, open-label trial (February to May 2021): CO2 monitors placed in twelve double-bed patient rooms across two geriatric wards of a Belgian hospital, staff instructed to open windows, increase air exchange and reduce crowding to keep CO2 at or below 800 ppm; primary outcome time per day above 800 ppm | F-0476 Laurent Monitors to improve indoor air carbon dioxide concentrations… (2022) | machine |
| Lung cancer | OR 1.18 (1.07–1.30) | adults of Jiangsu Province · home | population-based case-control study in Jiangsu Province, China, from 2003 to 2010: 2871 lung cancer cases and 8019 controls interviewed in person about the sources of indoor air pollution in their homes, with adjusted odds ratios from unconditional logistic regression and an integrated weighted risk score | F-1317 Fang et al. The Association Between Indoor Air Pollution and Lung Cancer… (2025) | machine |
| — | mean 6.51 | — · room | field experiment in rooms with natural ventilation: ventilation rates measured by tracer gas decay under cross ventilation and single-sided ventilation at several window opening ratios, with and without the air conditioner running, and the infection risk assessed with the Wells-Riley equation | F-1439 Park Natural ventilation strategy and related issues to prevent c… (2021) | machine |
| — | mean 11.20 | — · room | field experiment in rooms with natural ventilation: ventilation rates measured by tracer gas decay under cross ventilation and single-sided ventilation at several window opening ratios, with and without the air conditioner running, and the infection risk assessed with the Wells-Riley equation | F-1440 Park Natural ventilation strategy and related issues to prevent c… (2021) | machine |
| Polychlorinated biphenyls (PCBs) | one building; the study also reports encapsulation of the accessible caulk at 22 %, from 282 to 220 ng/m3, which was only marginally significant | — · school | intervention study in a school building with polychlorinated biphenyls in the caulk: indoor air concentrations measured before and after improved ventilation, encapsulation of accessible caulk, encapsulation behind convectors and construction of false walls, normalised and compared with the Wilcoxon rank sum test | F-1448 Mitigation of building-related polychlorinated biphenyls in … (2012) | machine |
| Chronic obstructive pulmonary disease (COPD) | OR 0.28 (0.11–0.73) | — · kitchen | cohort study of a fuel and ventilation intervention: households replacing biomass with biogas and improving kitchen ventilation followed for lung function decline and for chronic obstructive pulmonary disease | F-1717 Lung Function and Incidence of Chronic Obstructive Pulmonary… (2014) | machine |
| Carbon dioxide (CO₂) | no test statistic printed in the sentence | home-office workers · home office | measurement study in 21 home offices in Trondheim (Norway) during the COVID-19 pandemic: CO2, formaldehyde, TVOC, temperature and relative humidity logged with calibrated low-cost sensors for at least one week in winter (11 homes also in summer), predictors analysed with generalized estimating equations | F-0448 Alonso Assessing the indoor air quality and their predictor variabl… (2022) | machine |
| Carbon dioxide (CO₂) | difference 30 | kindergarten children · kindergarten classroom | experimental monitoring of CO2, indoor air temperature and relative humidity in Slovenian kindergarten classrooms of different architectural typologies over 125 days before and during the COVID-19 pandemic | F-0466 Lovec et al. Practical Impact of the COVID-19 Pandemic on Indoor Air Qual… (2021) | machine |
| Carbon monoxide (CO) | a null result stated without a number; the chimneys were self-built rather than installed to a design | — · home | cross-sectional study of determinants of indoor exposures in the department of Puno, Peru: households selected from a census of urban and rural communities by cooking fuel and chimney, with 24-hour indoor PM and carbon monoxide and with exhaled carbon monoxide and exhaled carboxyhaemoglobin measured in the cooks | F-0987 A cross-sectional study of determinants of indoor environmen… (2014) | 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.
Identifiers
- MeSH
- D014691
In the literature
- Exploring the impact of window design and ventilation strategies on air quality and thermal comfort in arid educational buildings (2025). Sci Rep. doi:10.1038/s41598-025-01362-y CKB 1150
- Ferdyn-Grygierek et al. Ventilation Methods for Improving the Indoor Air Quality and Energy Efficiency of Multi-Family Buildings in Central Europe. doi:10.3390/en17092232 CKB 0891
- Estimation of infiltration and ventilation rates in an office room with 145mm-diameter… (2023). doi:10.20944/preprints202304.0499.v1 CKB 0348
Studies in the Coridum Knowledge Base in which this term is used. The definition follows standard usage in WHO, ISO and textbook sources; it is not quoted from these papers.
CKB = document number in the Coridum Knowledge Base, our curated library of peer-reviewed studies. Follow the DOI for the original paper.
Cite this page
Coridum Research. Ventilation. Coridum Knowledge G-0067, 16 September 2026. https://coridum.com/k/G-0067/