- Blog
- 24 08 2023
- Tags: Architecture, Architecture and Ventilation, Interior Architecture
Can Covid-19 Spread Through Ventilation / HVAC Systems?
Health officials report that COVID-19 is most commonly spread when infected individuals sneeze or cough, and are exposed to the virus in droplets. These droplets can be directly inhaled over short distances or land on frequently touched surfaces. Large droplets typically settle to the ground about a meter away and do not remain suspended in the air, but small droplets can remain airborne for longer periods of time and over greater distances. Unless you are implementing COVID-19 precautions in your living and working spaces, small droplets can be carried to other areas by HVAC systems.
Viral droplets under 10 microns are a concern because they can remain suspended in the air for long periods of time. Although airborne viral droplets are not the primary means of transmission, they cannot be ignored. Many HVAC systems will pose an infection risk unless they are reconfigured.
Air Movement from High to Low Pressure Areas
Pressure differences create air movement, and suspended particles are carried. The 2019 coronavirus (SARS-CoV-2) tends to spread when released into a room at a higher pressure than its surroundings. Buildings with unbalanced ventilation systems are vulnerable to COVID-19 because there is limited control over air movement. Unbalanced HVAC systems also waste energy and should be fixed as soon as possible.
However, HVAC engineers can also use air pressure differences as a “prevention” measure. Rooms with potential coronavirus risks are kept under negative pressure, because air stays in. At the same time, other areas are kept under positive pressure to keep the virus out. For example, hospitals use this strategy in COVID-19 patient rooms to trap the virus.
Air Circulation with HVAC Ducts
Ventilation systems generally mix some of the fresh air taken from outside with some of the air exhausted from inside the building to obtain “mixed/make up” air. This poses a serious risk as it will allow air that may contain viruses to be recirculated to other areas within the building. In other words, more than one space served by the air handling unit is vulnerable.
To reduce the risk of COVID-19 transfer through air circulation, it is necessary to maximize the supply air and the air exchange coefficient inside. If possible, the building should be ventilated with 100% fresh air and exhaust air should not be re-introduced into the system. On the other hand, the weather conditions of the building and the capacity of the heating and cooling systems may not be sufficient to meet these requirements.
Improving air filters and increasing their filtration capabilities also helps prevent COVID-19. ASHRE recommends filters with a minimum MERV-13 standard.
While MERV 16 is the highest standard of hospital-grade filters that can capture many airborne microbes, HEPA filters are even more efficient.
However, ventilation system capacity can limit filter value. The most efficient filters also produce the highest pressure drop and can restrict ventilation.
An experienced plumbing contractor can determine the highest filter rating your air conditioning units will work with. You may also want to consider a fan upgrade to use more efficient filters.
Ultraviolet germicidal irradiation can kill not only coronaviruses, but also other harmful microbes such as Legionella bacteria and mold. HVAC engineers recommend UV disinfection systems for air handlers, where they can kill microbes before they spread to other construction sites.
Air Leakage in Energy Recovery Ventilators
Heat recovery ventilation units (HRVs) increase the efficiency of the system by transferring heat and air humidity between the outdoor air supply and the exhaust air. However, there may be leakage between the two air flows and viral particles in the exhaust may reach the supply air. If HRVs are well designed and maintained frequently, this risk is reduced, because air leakage is on average 1-3%.
IGK devices should be checked by an expert team and if the air leakage is too high, it should be bypassed or repaired. When high-efficiency HVAC filters are used with the IGK device, the risk is further reduced because; harmful particles at the micro level are captured before the incoming air reaches the interior spaces.
Covid-19 and Ventilation Systems





