The Statue of Liberty against a backdrop of high-rise buildings in New York City. Picture: Shutterstock
By Michael Tobias
COVID-19 has catapulted indoor air quality into the limelight as hospitals and health facilities work tirelessly to mitigate the spread of the coronavirus, educational bodies consider the best strategies to minimize infection before they reopen, and businesses contemplate how to protect their employees and customers from possible exposure to the disease.
Heating, ventilation, and air-conditioning (HVAC) is a vital element of construction. Well designed systems not only ensure optimal comfort inside buildings, they are also energy-efficient providing maximum functionality at a reasonable cost. But HVAC is an even more vital element of prevention strategies implemented to minimize the risk of coronavirus infection for building occupants.
One of the most significant issues is air quality, because of the way the disease is transmitted. And every single building in the city is vulnerable, whether it is a historical building, a civic building, a commercial building, or a building inhabited by families.
The New York City Hall is potentially as vulnerable to possible COVID-19 infection as any other building in the city. Picture: Shutterstock
Understanding How COVID-19 is Spread
There is an ongoing debate about exactly how COVID-19 is spread.
The first conclusion was that it was spread by respiratory droplets that resulted from infected people sneezing or coughing. The term droplet generally refers to tiny little bits of liquid spewed by a person that is greater than five microns in size.
If you were close enough the droplets could land on you, but more usually they landed on nearby surfaces, which is why there has been so much emphasis on keeping all services constantly sanitized. Either way, exposure to infected droplets could result in the spread of the disease.
More recently scientific evidence has revealed that the coronavirus infection could be spread by smaller microscopic aerosol particles that stay in the air much longer than smaller sprayed droplets. When spaces are not well ventilated, these can reach alarmingly high concentrations.
Explanations make it clear that the disease is airborne, whether for a few seconds until the droplets landed or for longer periods of time during which particles remained in the air. The difference, though, is that the droplets, which are bigger, tend to remain in the nose and throat area whereas the smaller particles are usually inhaled into the lower respiratory tract and the lungs.
Guidance from the World Health Organisation
The World Health Organisation (WHO) provides ongoing guidance in terms of the transmission of COVID-19 and offers advice on preventive measures that should be taken as part of their global Strategic Preparedness and Response Plan for COVID-19, which aims to control the virus by suppressing transmission and, in this way, preventing illness and death.
In a scientific brief published on 2 March 2020, WHO defined droplets as being more than 5 to 10 microns in diameter and described in detail how the disease was understood to be transmitted. Mostly, the risk was thought to be greatest if you were in close contact with anyone with infectious respiratory symptoms. But the dangers of indirect contact were also explained.
The explanation drew attention to the differentiation between droplet transmission and so-called airborne transmission which involves particles that are smaller or equal to 5 microns that can remain in the air for much longer periods of time and can be spread over distances further than 1 meter.
Updated on 9 July 2020, the WHO guidelines drew, additionally, on research undertaken after the global outbreak in an endeavor to try and learn more about the deadly virus and how it is transmitted. This time there is more information on possible transmission, which could be via:
- Direct contact or from droplets as described above, thought to be a very common means of transmission.
- Airborne transmission also described above and thought to be particularly virulent where ventilation is inadequate.
- Fomite transmission which contaminates objects and surfaces, though there is a lack of any evidence of this form of transmission.
Necessary steps to prevent transmission include maintaining social distance, avoiding over-crowded environments, wearing masks, self-quarantine, and practicing stringent hygiene and sanitization. The need for good environmental ventilation in all indoor (or closed) settings is also highlighted.
Importance of Improving Indoor Air Quality
The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) has provided detailed guidelines on what building owners and managers can do to improve indoor air quality and, in this way, reduce the risks associated with COVID-19.
Generally, it is thought that airborne transmission of the disease is associated with both inadequate ventilation and high occupancy. Lockdown has played a major role in minimizing the second factor, but more active measures need to be taken to improve ventilation. Some systems can be upgraded quite easily, while others may need to be totally overhauled.
The best approach is to have a professional assessment of the building by a qualified HVAC engineer who will identify areas of vulnerability and suggest ways to optimize ventilation systems and improve air purification and HVAC filtering methods.
ASHRAE recommends increasing the circulation of outdoor air as much as possible, though this will depend on the quality of the air outside the building. Clearly, if the building is located in an area where there is an air pollution problem, other steps will need to be taken. Generally, using disinfection systems that are ozone-based will also help to improve ventilation and make buildings much healthier.
When a qualified HVAC engineer undertakes an air quality assessment, he or she will also identify any other germs or biological hazards that might be present in the building and make recommendations to rectify the environment as quickly and cost-effectively as possible.
This is a good route to take before opening up buildings after COVID-19 lockdown. Rather be safe than sorry.
Michael Tobias is the founder and principal of Nearby Engineers and New York Engineers, an Inc 5000 Fastest Growing Company in America. He leads a team of more than 30 mechanical, electrical, plumbing, and fire protection engineers from the company headquarters in New York City, and has led numerous projects in New York, New Jersey, Chicago, Pennsylvania, Connecticut, Florida, Maryland, and California, as well as Singapore and Malaysia. He specializes in sustainable building technology and is a member of the U.S. Green Building Council.