How ventilation systems can prevent the spread of Coronavirus
HVAC systems appear to be held responsible for the spread of COVID-19 disease but should rather be recognized as a helpful resource in the battle against it.
Rome 14/05/2020 – Media have been reporting confusing information in relation to the danger of using Air Conditioning systems during the COVID-19 pandemic. Many articles and news, have been mentioning a recent Chinese study which analyses the outbreak of Coronavirus in a restaurant in Guangzhou (“Evidence for probable aerosol transmission of SARS-CoV-2 in a poorly ventilated restaurant”, https://doi.org/10.1101/2020.04.16.20067728), using it to support the idea that AC systems might be responsible for the spread of Coronavirus.
While the idea that AC systems might be responsible for spreading the virus doesn’t seem to be backed by substantial scientific evidence, these interpretations of the above-mentioned study totally miss the point of the study itself.
The study titled “Evidence for probable aerosol transmission of SARS-CoV-2 in a poorly ventilated restaurant”, is actually highlighting the fact that the restaurant in Guangzhou had a poor ventilation system. In fact, the ventilation rate in the restaurant was between 2.7 and 3.7 m³/h per person – 10 times lower the ventilation rate advised by most authorities and professional associations.
The study also highlights how Ventilation Systems are an important resource to clean indoor environments from contaminants, including viruses, thanks to the extraction of the indoor air and the introduction of filtered air from the outdoor environment. The point is that, once a SARS-CoV-2 positive individual enters a building, the only way to minimize the possibility of infection for other occupants, is cleaning indoor air through ventilation systems.
So, in the current situation caused by the spread of the Coronavirus, HVAC technologies can have an important role in the prevention of the infection from SARS-CoV-2. This point has been stressed by important air conditioning, heating and ventilation associations like REHVA (Federation of European Heating, Ventilation and Air Conditioning Association) and ASHRAE (American Society of Heating, Refrigerating and Air-Conditioning Engineers), who recently pointed out the importance of the contribute that Ventilation technologies can provide in the current situation.
The Coronavirus pandemic shows that the risk of infection in public confined spaces is of the utmost importance and cannot be ignored. The Airborne transmission mode is considered to be the main one. In fact, recent studies conducted by the , clearly demonstrate that SARS-CoV-2 is spread via bioaerosols generated directly by patients’ exhalation. Also, there have been many studies suggesting that insufficient ventilation can increase the possibilities of transmissions. Therefore, ensuring proper ventilation in indoor environments such as offices, classrooms and public spaces is essential to reduce the risk of infection.
More specifically, the study “Association of infected probability of COVID-19 with ventilation rates in confined spaces: A Wells-Riley equation-based investigation”, employed a mathematical model to estimate the correlation between infection probability and ventilation rate. This study shows a close correlation between the ventilation-rate and infection possibility. In fact, the study clearly shows that the higher is the ventilation rate per hour in a room, the lower is the possibility of infection for the occupants.
That also means, once an asymptomatic infector enters a public confined space, the risk of infection for other occupants is quite high if there is not proper ventilation in the building, or there is no ventilation at all.
So, while the risk of potential airborne transmission in indoor spaces cannot be ignored, Ventilation technologies are preventive measures that should be widely adopted to reduce the risk of airborne transmitted infection.
The latest scientific studies and findings, also reinforce the position of medical organizations and institutions such as the WHO (World Health Organization) and the ISS (Istituto Superiore di Sanità – Rome, Italy), which all agree on the importance of fresh air exchange rate.
Another important clarification on the subject-matter, has been provided by Professor Le Foche.
Professor Le Foche, is a clinical immunologist at Policlinico Umberto I in Rome. He has been supporting Daikin Applied Europe in the reviewing the company’s organizational system, so that the company could be able to resume manufacturing operations after the lockdown period caused by the COVID-19 pandemic.
“From a medical standpoint, I can say that a well-designed ventilation system, which can guarantee the correct air exchange in indoor environments, can really help in reducing the spread of the virus. That has been confirmed by several scientific studies. Also, the introduction of clean air and the simultaneous extraction of exhausted air is a recommended action. It helps to purify the indoor air, hence reduces the possibility of infection among the occupants of a building”.
The conclusion reached by all experts, is that ventilation systems contribute in reducing the concentration of SARS-CoV-2 in the air, and therefore the risk of transmission, especially in offices and public indoor environments. Of course, to get the most out of the use of Ventilation systems and technologies, it is important to carry out proper maintenance activities. It is therefore necessary to proceed with normal cleaning and maintenance activities to ensure correct operation.
Another important aspect related to the use of ventilation systems to clean the air in indoor environment, then, is the level of filtration of the outdoor air that the systems can guarantee. Since we do not want to introduce outdoor contaminants in indoor environments during the air exchange process, it is important that ventilation systems can adequately filter and clean the outdoor air.
So, instead of worrying about air conditioning, facility managers should use their ventilation system – if they have one available – to minimize the possibility of infection between buildings occupants. And if they have not a ventilation system available, they should be aware of the importance of such systems as a preventive measure.
In conclusion, properly engineered Ventilation systems represent an important solution to protect people from the spread of SARS-CoV-2 during this pandemic. It is important to understand that ventilation systems need to be properly sized in order to guarantee the adequate air exchange rate in indoor environment and properly clean the air. Along with special attention to air exchange rate, then, it is important to acknowledge the importance of highly efficient filters, able to ensure the highest level of air filtration and keep indoor environments clean at all times.
It is fundamental to understand that HVAC systems are a resource in this battle against the spread of Coronavirus and should be acknowledged as necessary measures to prevent the spread of SARS-CoV-2.
– Association of infected probability of COVID-19 with ventilation rates in confined spaces: a Wells-Riley equation based investigation, https://www.medrxiv.org/content/10.1101/2020.04.21.20072397v1
– Ventilation rates and health: multidisciplinary review of the scientific literature, Indoor Air 2011; 21: 191–204 wileyonlinelibrary.com/journal/ina
– Lynch RM, Goring R, Practical Steps to Improve Air Flow in Long-Term Care Resident Rooms to Reduce COVID-19 Infection Risk, Journal of the American Medical Directors Association (2020), doi: https://doi.org/10.1016/j.jamda.2020.04.001.
– Effects of indoor environmental parameters related to building heating, ventilation, and air conditioning systems on patients’ medical outcomes: A review of scientific research on hospital buildings, https://europepmc.org/article/med/30588679
– Evidence for probable aerosol transmission of SARS-CoV-2 in a poorly ventilated restaurant, https://doi.org/10.1101/2020.04.16.20067728
– Natural Ventilarion for infection Control in Health-Care Settings, https://www.ncbi.gov/books/NBK14278/