Earlier the preventive measures for fighting against the novel COVID-19, commonly known as Coronavirus, was majorly focused on avoiding large infection carrying droplets (>5-10 μm) when an infected person sneezes or coughs, while ensuring the surrounding surfaces and objects are disinfected. However as airborne transmission of coronavirus has become a widely debated topic among various medical researchers and experts, more light has been shed on the possibility of airborne COVID-19 transmission.
Scientists now believe that are scientific evidences that suggest airborne transmission of coronavirus is possible. The transmission can happen in the form of tiny microscopic droplets (<5 μm) known as aerosols. The latest guidance from WHO has recognized the imminent threat of coronavirus infection by exposure to aerosols in crowded indoor spaces.
Seeing the rising risk of airborne COVID-19, indoor air quality in buildings has become crucial. ASHRAE(The American Society of Heating, Refrigerating and Air-Conditioning Engineers) has released a thorough guidance on how to improve indoor air quality thus reducing the risk of infections. The guidance is mainly focused on:
Increased outdoor air ventilation, with zero air recirculation.
Upgrading air filters to medical grade, which means MERV 13 or better.
Use of Ultraviolet Germicidal Irradiation, or UVGI, for air and surface disinfection.
ASHRAE Guidance for Controlling Airborne COVID-19 Transmission
The chances of airborne transmission are more likely to happen in indoor spaces with high occupancy and deficient ventilation. Higher indoor occupancy directly translates to higher risk or transmission if the viral microscopic droplets are not removed by an efficient ventilation system.
Ventilation system improvements depend upon the existing HVAC installation. Although some systems can be easily reconfigured to the desired settings, others may need component upgrades for efficient ventilation. It has become more and more evident that increasing outdoor air supply and elimination recirculation of air is one of the most effective ways of tackling virus transmission.
Since aerosols are such tiny droplets, filter upgrades and UVGI can provide additional protection against airborne transmission. Medical grade air filters with MERV rating of 13 or higher coupled with UVGI systems with UV-C light capable of killing germs by destroying their DNA are highly recommended. Building owners are thus recommended to use right products.
Adapting to Best Air Quality Measures for Buildings
Depending upon the type of ventilation system and HVAC configuration, the most effective measures can vary. Thus, a thorough professional assessment of the property is highly recommended and is the best starting point for improving indoor air quality. Building Automation System (BAS) can be used as they eliminated the need manual adjustments making it easier to reconfigure HVAC systems.
Weather conditions also need to be considered as they can limit the effectiveness of outdoor airflow. For example, air conditioning systems or space heating systems may be overwhelmed if the outdoor air is too hot or cold. This may lead to unsuitable indoor temperatures for indoor occupancy.
Fan inspection is highly recommended before upgrading air filters or you might end up installing air filters that restricts airflow. This can have a detrimental effect on the building. UVGI must be deployed by professionals as UV lights are capable of causing skin or eye damage.