HVAC systems may appear to play a part in the spread of COVID-19, however they should be recognised as a helpful resource in the battle against it.
There has been some unclear information in relation to the danger of using Air Conditioning systems during the COVID-19 pandemic. There has been mention of 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”), using it to support the idea that AC systems might be responsible for the spread of Coronavirus.
There is no substantial scientific evidence to back these findings, yet the interpretations of the above-mentioned study completely 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 the significance of ventilation systems as an important resource to provide clean indoor environments from contaminants, including viruses. This is thanks to the extraction of the indoor air and the introduction of filtered air from the outdoor environment. The point the study makes is that once a SARS-CoV-2 positive individual enters a building, the only way to minimise the possibility of infection of other occupants, is using ventilation systems to clean the air.
In our current global position following the spread of the Coronavirus, HVAC technologies can play 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 such a 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 ventilation technologies and their contributions to provide clean air and reduce the spread of viruses.
The Coronavirus pandemic has highlighted that there is a high risk of infection in confined public spaces and the reduction of risk is of uttermost importance.
Recent studies clearly demonstrate that SARS-CoV-2 can be spread via bio aerosols generated directly by exhalation. There have also been many studies suggesting that insufficient ventilation can increase risk of transmissions. Therefore, by ensuring proper ventilation in indoor environments such as offices, classrooms and public spaces, the risk of infection can be reduced.
One recent 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 demonstrations a close correlation between the ventilation-rate and possibility of infection. The results show that the higher the ventilation rate per hour in a room, the lower is the possibility of occupant infection.
This also means that if an asymptomatic, infectious person enters a confined public space, the risk of infection for other occupants is high if there is no proper ventilation in the building, or there is no ventilation at all.
While there is a risk of potential airborne transmission in indoor spaces, ventilation technologies are can be used as preventive measures and should be widely adopted to reduce the risk of airborne transmitted infections.
The latest scientific studies support the position of medical organisations 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.
Professor Le Foche, is a clinical immunologist at Policlinico Umberto I in Rome, who has provided clarification on the importance of fresh air exchange. He has been supporting Daikin Applied in reviewing the company’s organisational system, so that manufacturing operations could resume 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”.
Experts agree that ventilation systems play a role in reducing the concentration of SARS-CoV-2 in the air, and therefore minimising the risk of transmission, particularly in offices and public indoor environments. It is important to properly maintain the ventilation systems and technologies, and carry out proper maintenance activities to ensure the systems are functioning optimally. It is therefore necessary to proceed with normal cleaning and maintenance activities to ensure correct operation.
Outdoor air contaminants must be eliminated in indoor environments during the air exchange process. It is important that ventilation systems can adequately filter and clean the outdoor air and the level of filtration can be guaranteed to provide clean air and remove all outdoor contaminants in an indoor environment.
Ventilation systems should be used by facilities managers to minimise the possible infections between occupants. If there is no ventilation system available, they should be aware of the importance of such systems as a preventive measure.
Properly engineered ventilation systems can provide a 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 environments and properly clean the air. Along with special attention to air exchange rate, it is important to acknowledge the importance of highly efficient filters, which are 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 the battle against the spread of Coronavirus and should be acknowledged as necessary measures to prevent the spread of SARS-CoV-2.
References
– 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 Ventilation for infection Control in Health-Care Settings, https://www.ncbi.nlm.nih.gov/books/NBK143284/
