Question & Answer

Does the use of air conditioning spread COVID-19?

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Claims have been circulated on social media that using air conditioning may lead to the spread of COVID-19.
Heating, ventilation and air conditioning (HVAC) systems are used in indoor spaces to provide comfortable environmental conditions of temperature and humidity (moisture in the air).
There are various types of HVAC systems. Ventilation systems provide clean air by exchanging indoor and outdoor air and filtering. Air conditioning systems provide varying temperatures and take excess moisture from the air.
Air conditioning systems can be part of an integrated HVAC or stand-alone system. Stand-alone air conditioning systems generally recirculate air without exchanging or mixing it with outdoor air.
The various types of HVAC systems mean that it is difficult to generalise the results of studies that have taken place to date on the transmission of previous coronaviruses (e.g. SARS) through these systems.
There is not enough high-quality evidence to support the claim that COVID-19 is spread through air conditioning systems.
In spaces and buildings such as homes, schools and offices, the World Health Organization (WHO) recommends increased ventilation through natural (e.g. opening windows) or mechanical (e.g. HVAC systems that introduce outdoor air) means, preferably without systems that recirculate the air.
Air conditioning and industrial ventilation systems in public spaces and buildings should be inspected, maintained, and cleaned regularly to ensure systems are working properly
The European Centre for Disease Prevention and Control states that well-maintained HVAC systems can help to decrease the spread of COVID-19.

Things to Remember

Beware of claims that are based on a single study. Ask if other studies examine the same question and, ideally, if there a careful summary of all the relevant studies.
Beware of claims that are based on before and after comparisons, and when people don’t say what a treatment was compared to. Remember: Ask what the treatment was compared to and whether it was a fair comparison.
Whenever possible, use up-to-date careful summaries (systematic reviews) of fair comparisons to inform decisions.

Reviewers

Lead Researcher: Dr. Claire Beecher, HRB-Trials Methodology Research Network & Evidence Synthesis Ireland, University of Galway
Reviewed by: Prof. Declan Devane, School of Nursing and Midwifery, HRB-Trials Methodology Research Network, Evidence Synthesis Ireland & Cochrane Ireland, University of Galway.
Topic Advisor: Prof. Andrew Murphy, General Practice, University of Galway, Health Research Board Primary Care Clinical Trials Network Ireland
Public and Patient Advisor: Anne Daly, PPI Ignite, University of Galway.
Journalist Advisor: Dr. Claire O’Connell, Contributor, The Irish Times.

Conflict of Interest Statement: The authors have no financial or other conflicts of interest for this health claim summary.

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