Research into the transmission of SARS-CoV-2 has presented ‘overwhelming evidence’ that inhalation of the virus ‘represents a major transmission route for coronavirus disease 2019 (COVID-19).’[1] In response, leading bodies, such as the Centers for Disease Control and Prevention (CDC)[2] and the European Centre for Disease Prevention and Control (ECDC)[3], advise improving air ventilation in enclosed spaces in addition to following existing guidance, e.g. washing hands, maintaining social distancing, and wearing a face mask. Monitoring CO2 concentration provides an easy way of assessing air quality and maintaining good air ventilation. PASS Ltd offers a range of indoor air quality monitors suitable for this purpose, including Chauvin Arnoux’s CA 1510 IAQ Tester.

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Aerosol Transmission

Aerosols are respiratory droplets of less than 100 micrometres; they are expelled when breathing, speaking, shouting or singing. Unlike droplets, which are larger than 100 micrometres and fall to the ground within seconds and usually within a 2m radius of the source, aerosols linger in the air for hours and can travel over two meters.[4] The longer the infected individual spends in a poorly ventilated area the greater the concentration of contaminated aerosols and, therefore, the more likely the risk of transmission. Singing and shouting also expedite aerosol concentration as these activities produce a greater number of respiratory particles.[5] The build-up of aerosols in poorly ventilated, enclosed spaces, as well as increased exposure to the air in these spaces, can result in super-spreading events.[6]

There have been a number of COVID-19 outbreaks that seem to provide strong evidence of aerosol transmission. These include a choir practice in Washington State that resulted in 52 cases of COVID-19 (an infection rate of 85.2%); ten cases contracted across three families that had eaten at a poorly-ventilated restaurant in Guangzhou, China on the 23rd January 2020; and an outbreak in a South Korean call centre that affected 43.5% of the ninth-floor workforce. [7]

Improving Air Ventilation

Effective indoor ventilation is especially important when it comes to preventing the transfer of SARS-CoV-2/ COVID-19 as often infected persons are asymptomatic and will be unaware that they are breathing out aerosols.

To illustrate the positive effects of ventilation, the Spanish newspaper, El País, used the COVID-19 Airborne Transmission Estimator, developed by Professor José Luis Jiménez and a team of scientists at the University of Colorado, to estimate the risk of infection under various circumstances. One example analysed a bar with a reduced 50% capacity. In the simulation, there were three members of staff and fifteen guests including an individual infected with coronavirus, Patient 0. When no measures were taken Patient 0 infected fourteen others; this was the worst-case scenario. When masks were worn only eight people were infected. However, when the room was properly ventilated and a cap was placed on the length of time customers could spend in the bar, the simulation estimated that Patient 0 would only infect one other person.[8]

There are a number of ways to improve ventilation in enclosed spaces. The most simple and effective way is to open doors and windows to allow fresh air to pass through the room and filter out contaminants.[9] Research conducted by the environmental campus, Bielefeld, suggests that cross ventilation provides the most efficient and successful method of reducing CO2 and aerosol concentrations as a complete air exchange takes place during this process.[10]

It is also recommended that air filters in HVAC systems are changed regularly. This rids the HVAC system of contaminants that may be circulated around the room and prevents the build-up of mould which could present its own hazards.[11]

CO2 Monitoring

Measuring CO2 offers a good indication of the efficacy of air ventilation as humans also breathe out carbon dioxide gas which lingers in the air much like aerosols. A high concentration of CO2 will often indicate poor ventilation. However, Anna Hartmann and Martin Krieger of the Institute of the Technical University of Berlin explain that ‘with a high air exchange, both low CO2 concentrations and low aerosol concentrations can be achieved. The lower the aerosol concentration, the lower the dose of aerosols that a person in the room inhales and therefore the risk of infection.”[12]

Irrespective of preventing COVID-19 outbreaks, it is important to ensure low concentrations of CO2 as high levels can lead to ‘headaches, dizziness, fatigue, restlessness and nausea’.[13]

PASS Ltd offers a range of indoor air quality monitors, including Chauvin Arnoux’s CA 1510 Indoor Air Quality Tester. This IAQ monitor supports flexible mounting and can measure and log CO2 concentrations, air temperatures and air humidity simultaneously. It can store up to one-million readings.

Furthermore, the CA 1510 features a colour-coded alarm which will alert the user when the carbon dioxide concentration reaches average (1000ppm) and high (1700ppm), allowing corrective action to be taken immediately. This IAQ tester is also compatible with Chauvin Arnoux’s Android App, allowing managers or proprietors to monitor the air quality remotely via a smartphone or tablet.

Chauvin Arnoux’s video (below) and case study offer further information regarding the CA 1510 Indoor Air Quality Tester’s role in preventing COVID-19.

Further Information

Browse our range of air quality testers here. For more information regarding any of these models, please do not hesitate to contact our sales team on 01642 931 329 or via our online form.

For hand sanitiser, face masks, IR thermometers, and temperature-screening thermal cameras, please visit our COVID-19 section.

For more information regarding the 'Role of Ventilation in Controlling SARS-CoV-2', please see this CEN and BSI UK document.


[1] Melissa A. McDiarmid, Linsey C. Marr, Donald K. Milton, Kimberly A. Prather, Robert T. Schooley, Mary E. Wilson, ‘Airborne Transmission of SARS-CoV-2’, in Science, 370 (Oct 16 2020), 303-304, last accessed 17 November 2020 <https://science.sciencemag.org/content/370/6514/303.2>

[2] CDC, How COVID-19 Spreads, last accessed 17 November 2020 <https://www.cdc.gov/coronavirus/2019-ncov/prevent-getting-sick/how-covid-spreads.html>

[3] ECDC, Heating, ventilation and air conditioning systems in the context of COVID-19: first update, last accessed 17 November 2020 <https://www.ecdc.europa.eu/sites/default/files/documents/Heating-ventilation-air-conditioning-systems-in-the-context-of-COVID-19-first-update.pdf>

[4] McDiarmid, Marr, Milton, Prather, Schooley, Wilson, ‘Airborne Transmission of SARS-CoV-2’

[5] ECDC, Heating, ventilation and air conditioning systems in the context of COVID-19: first update

[6] McDiarmid, Marr, Milton, Prather, Schooley, Wilson, ‘Airborne Transmission of SARS-CoV-2’

[7] ECDC, Heating, ventilation and air conditioning systems in the context of COVID-19: first update

[8] Heather Galloway, ‘A room, a bar and a classroom: how the coronavirus is spread through the air', in El País, last accessed 17 November 2020 <https://english.elpais.com/society/2020-10-28/a-room-a-bar-and-a-class-how-the-coronavirus-is-spread-through-the-air.html>

[9] CO2Meter, Indoor Air Quality COVID-19 Facts, last accessed 17 November 2020 <https://www.co2meter.com/blogs/news/indoor-air-quality-covid-19-facts>

[10] Chauvin Arnoux, Testing the indoor air quality with C.A 1510 for COVID-19 prevention, last accessed 17 November 2020, available here.

[11] CO2Meter, Indoor Air Quality COVID-19 Facts

[12] Chauvin Arnoux, Testing the indoor air quality with C.A 1510 for COVID-19 prevention

[13] CO2Meter, Indoor Air Quality COVID-19 Facts