Among the numerous questions that linger in the midst of the COVID-19 pandemic, one of them is whether the virus can be transmitted through air-conditioning systems.
At the moment, there is currently no evidence that Covid-19 can spread through air-conditioning systems, according to Professor Leo Yee Sin, executive director of the National Centre for Infectious Diseases (NCID).
While a recent study by NCID researchers had found that the virus causing Covid-19 could be found in isolation facilities, including in an air duct connected to the room of one of the patients, it does not prove that this disease is an airborne one.
Studies have shown that the main way the virus is spread is through respiratory droplets.
Additionally, in the knowledge of Eurovent (Europe's Industry Association for Indoor Climate, Process Cooling, and Food Cold Chain Technologies), no authorities have yet issued guidance for the operation of (mechanical) ventilation systems.
However, also according to one air quality expert, the crisis onboard the quarantined Diamond Princess cruise ship in Japan showed how germs can spread rapidly through air conditioning systems that can’t filter out particles as small as the new coronavirus.
So there is still a lot of uncertainty and still a lot to learn from the new COVID-19 outbreak. One thing that is certain is the novel coronavirus affects the lungs. It is a well-known fact that we spend approximately 90% of our time indoors and given the current situation that percentage has certainly gone up. Another fact to consider is that the average adult, when resting, inhales and exhales about 7 or 8 litres of air per minute. That totals about 11,000 litres of air per day. It is thus pertinent now that we need to look at maintaining good indoor air quality, and that directly means looking closely at our HVAC or air conditioning systems.
ASHRAE (The American Society of Heating, Refrigerating and Air-Conditioning Engineers) guidelines provide some information on the best way to operate HVAC systems to help in preventing the spread of pathogens. Hassan Younes, director & partner at GRFN (previously known as Griffin Consultants), guides FMME in that direction by listing them out:
• Increase outdoor air ventilation (use caution in highly polluted areas); with a lower population in the building, this increases the effective dilution ventilation per person.
• Disable demand-controlled ventilation (DCV).
• Further open minimum outdoor air dampers, as high as 100%, thus eliminating recirculation (in the mild weather season, this need not affect thermal comfort or humidity, but clearly becomes more difficult in extreme weather, i.e., summer in the UAE).
• Improve central air filtration to the MERV-13 or the highest compatible with the filter rack, and seal edges of the filter to limit bypass.
• Keep systems running longer hours, if possible 24/7, to enhance the two actions above.
• Consider portable room air cleaners with HEPA filters.
• Consider UVGI (ultraviolet germicidal irradiation), protecting occupants from radiation, particularly in high-risk spaces such as waiting rooms, prisons and shelters.
Additionally, making sure heat recovery wheels are set up correctly and the leakage from the exhaust to the outside air section is minimal.
Hassan Younes, director & partner at GRFN
Younes says: “Preventive HVAC maintenance should happen to make sure outside air and exhaust equipment, dampers, and filters are working properly. When it comes to filters, it is wise to assume that filters have active microbiological material on them. Whether this represents an important infectious disease risk from viruses is not known, but the precautionary principle would suggest that care should be taken. This becomes particularly important in any building (including a home) where there are known or likely cases of any infectious disease including COVID-19 and also extends to portable air cleaner filters and vehicle cabin air filters. Filters should be changed with the system turned off, while wearing gloves, with respiratory protection if available, outdoors if possible, and disposed of in a sealed bag. Additionally heat recovery wheel should be checked.”
Dr. Iyad Al-Attar, a mechanical engineer, business innovator and air filtration consultant, weighs in, and shares his thoughts on air filtrations systems that prevent the spread of pathogens. He says: “The SARS-CoV-2 has paid us a surprise visit to find us pledging allegiance to sketchy filter specifications that tolerate regenerating disposal filters, inappropriately selecting filters, entertaining conventional filter design and prompting single-stage filtration solutions for most applications. How can we move forward if we belittle the impact of climate change and air pollution, misunderstand filtration standards and allow unqualified maintenance teams to slice and dice our air quality? Evidently, imminent filtration mistakes can be expensive, leading to irrecoverable performance losses in HVAC equipment.”
Dr. Iyad Al-Attar, a mechanical engineer, business innovator and air filtration consultant
Dr. Al-Attar, who has has become recently active in the field of air pollution in an effort to research its control measures, says: “Most of residential filtration relies on a single stage filtration, which is usually a washable metallic filter. When high efficiency particulate air (HEPA) filters are used, they have to be preceded to a minimum of three filtration stages, namely, fresh air, pre, and fine filtration. In the past six decades, the focus has been to only filter solid particles with maximum efficiency for offices & shopping malls, for example, of around 65%. Minor attention to micro-organism filtration and gaseous removal was given for non-healthcare facilities. Although Absolute filters are used in operating theaters, a serious consideration to install them in other zone of the healthcare/hospital is of a paramount importance. Further, while installing absolute filters in operating theater help capture microorganisms, it does not necessarily sterilise the air. Particulate filters remove solid particles of different sizes at various efficiencies depending on the application. However, they are incapable of controlling odour and their efficiency in removing gaseous pollutants ranges from slim to non-existent.”
The other solution for maintaining a good indoor air quality is through the use of air purifiers.
Gem McLuckie, advanced research scientist in microbiology at Dyson, says that given the hot temperatures, the Middle East region is defined by air conditioning systems which constantly change the air quality because of the pollutants present in the air.
McLuckie adds: “Air that is constantly circulating indoors be it at home, the office or somewhere as sterile as hospitals can contain particles ranging from dust and pet dander to allergens and volatile organic compounds from cigarette smoke and solvents. While opening a window for some fresh air may sound like an obvious solution, depending on where you are, outdoor air often brings in more toxins – be it from vehicle exhaust or in part of the Middle East dust. All that will prove to be detrimental to our newly adjusted lifestyles in times of strict lockdowns.”
Dyson air purifiers have been scientifically proven to remove many of these microscopic allergens but to be truly effective a more holistic approach is required. Many of these particles can accumulate in furniture, carpets, textiles and bedding so require regular cleaning. A two-pronged approach that involves the use of air purifiers in conjunction with thorough cleaning – using a fully sealed vacuum cleaner – is the most effective solution to ensure improved indoor air quality.
Talking more about air purifiers, McLuckie adds: “Air purifiers can play a vital role to ensure you breathe in good quality air that is free from contaminants and allergens. There are a few key factors people should look out for when considering installing an air purifier indoors. Ideally, they should have fully sealed filters that prevent the airflow from bypassing the filter media and as a result you can be sure the machine is filtering the air of particles and gases.
“Dual filters such as HEPA (high efficiency particulate air) and other types of particle filter remove microscopic pollutants from the air like dust, pollen and pet dander. A good quality air purifier should reduce asthma symptoms through an activated carbon filter that will absorb VOCs, NO2 and other gases, while fan functionality allows for clean air to be projected across the room.”
Dyson has engineered its air purifiers based on extensive scientific research and study. These devices are designed to remove gases and capture 99.97% of airborne particles as small as 0.3 microns. This includes particles the size of bacteria and viruses.
Modern buildings such as hospitals, warehouses, and even homes can be up to 5 times more polluted than the air outside from the build-up of formaldehyde from a wide range of items. This includes new textiles such as carpets, which release toxins into the air. Dyson’s research, design, and development teams focus on solving such problems by inventing machines that capture and remove these harmful pollutants at a molecular level, so as to have cleaner air.
Gem McLuckie, advanced research scientist in microbiology at Dyson
Air purifiers and filters apart, are the current regulations for IAQ coronavirus-ready?
Dr. Al-Attar reponds: “Greater emphasis are usually placed on thermal comfort single-handedly when air conditioning is addressed. Minor attention is paid to air quality and the role of air filtration to provide it. Fans and coils get the lion share in terms of R&D investments as far as air-handling units are concerned. The methodologies of enhancing indoor air quality and the way we have been managing our indoor and outdoor environment lack precision. We failed to utilise the current HVAC technologies as far as air quality is concerned. We have not put a lid on ignorance and a plug on compliancy in the ways we surrender ourselves to the conventional HVAC maintenance practices.
Younes gives a detailed explanation on the current regulations that mainly follow international standards, namely ASHRAE standard 62.1. He says: “One of the few things that are proposed to be changed in the 62.1 standard is to have a minimum relative humidity of 40%. Some studies showed that the lower the humidity the higher the possibility of airborne transmission. Also, heat recovery devices may carry over virus attached to particles from the exhaust air side to the supply air side via leaks. Recovery wheels may be sensitive for considerable leaks in the case of poor design and maintenance. For properly operating rotary heat exchangers, fitted with purging sectors and correctly set up, leakage rates are about the same as that of plate heat exchangers being in the range of 1-2%. For existing systems, the leakage should be below 5%, and has to be compensated with increase of outdoor air ventilation. However, many rotary heat exchangers may not be properly installed. The most common fault is that the fans have been mounted in such a way that higher pressure on the exhaust air side is created. This will cause leakage from extract air into the supply air. The degree of uncontrolled transfer of polluted extract air can in these cases be of the order of 20%, and that is not acceptable. Because the leakage rate does not depend on the rotation speed of rotor, it is not needed to switch rotors off. Normal operation of rotors makes it easier to keep ventilation rates higher. It is known that the carry-over leakage is highest at low airflow, thus higher ventilation rates are recommended. If leaks are suspected in the heat recovery sections, pressure adjustment or bypassing (some systems may be equipped with bypass) can be an option in order to avoid a situation where higher pressure on extract side will cause air leakages to supply side. Pressure differences can be corrected by dampers or by other reasonable arrangements. In conclusion, we recommend to inspect the heat recovery equipment including the pressure difference measurement. To be on the safe side, the maintenance personnel should follow standard safety procedures of dusty work, including wearing gloves and respiratory protection. Virus particle transmission via heat recovery devices is not an issue when a HVAC system is equipped with a twin coil unit or another heat recovery device that guarantees 100% air separation between return and supply.”
Dyson air purifiers are designed to remove gases and capture 99.97% of airborne particles as small as 0.3 microns.
ASHRAE to the rescue
Younes explains that in light of the COVID-19 pandemic, serious concerns arise regarding the capacity of healthcare facilities to provide both negative pressure isolation and properly pressurised intensive care spaces. In recent days, guidance has been developed to assist healthcare facilities in preparation to receive increasing numbers of COVID patients. This guidance is based on input from ASHRAE. guidelines outline specific strategies for increasing capacity for negative pressure isolation rooms in the short term. Of particular importance to healthcare facility managers are strategies to modify spaces, air handling systems and controls to attain the necessary air pressure control for treating COVID patients.
Additionally, ASHRAE recommends the following for hospitals facility managers: Review patient entrance and flow patterns throughout the facility; Evaluate accuracy of space pressure relationships – especially airborne infection isolation rooms; and Revise contingency plans for a possible occurrence in which demand for isolation rooms exceeds capacity.
Dr. Al-Attar concludes by saying: “It is imperative to believe that accelerating globalisation, industrialisation, rapid urbanisation, and population growth, if not rationally controlled, would further drive the emerging issues of climate change in the wrong direction. This would necessitate smarter ways of urban designing, living, and functioning as well as generating power more efficiently and using it more economically. We continue to hang our polluted hats on the environment rather than establish an intrinsic understanding of the escalated climate change. Furthermore, we ought to realise that while clean air is limited and rare, our climate is changing, our lungs are polluted, guidelines are still evolving, our actions are insufficient and SARS-CoV-2 is here.”