Much More Than Much Hot Air: How HVAC Systems Ventilation Ratings Can Help Reduce COVID-19 Transmission

Much More Than Much Hot Air: How HVAC Systems Ventilation Ratings Can Help Reduce COVID-19 Transmission

There is great uncertainty about how buildings can contribute to or prevent the spread of COVID-19. Engineers and other experts have indicated that changes in building operations can reduce the transmission of COVID-19. Similarly, federal agencies have recommended that the best way to reduce the potential for circulated or persistent COVID-19 indoors is to increase fresh air ventilation and return air filtration whenever available but without the existing HVAC system. Affecting the system.

Businesses today should be familiar with the concerns and pitfalls that can arise when modifying heating, ventilation, and air conditioning (HVAC) systems. Facility operators and managers should carefully consider their options before modifying an HVAC system because of the complexity of such operational adjustments.

Air quality considerations

Air Changes vs. Ventilation – When people talk about “air changes,” they usually refer to the number of air changes per hour provided by the ventilation system. In most ventilation systems, the supply air coming from a ventilation unit (AHU) is a mixture of extract air (RA) and outside air (OA). Newer systems often consist of circulating air devices in the room, such as chilled beams (CBs) or fan coil units (FCUs), combined with dedicated outside air systems (DOAS). As a result, the ACH rate is based on a mixture of OA and RA or just OA, depending on the configuration of the ventilation system.

Filtration – A typical school and office AHU is designed to use filters with MERV 8 ratings. The higher the MERV rating, the higher the filter effectiveness. Some professional organizations have recommended increasing filtering to MERV 13-rated filters to improve building readiness. Any change in filtration should include an assessment of the associated fans, as increasing filtration efficiency usually requires additional fan power and space for filters.

Local HEPA filter units – Another option is to use local standalone high efficiency particulate matter (HEPA) filter units that can be plugged into a wall socket. These devices are equipped with replaceable HEPA filters that circulate the room air. Even with properly functioning HVAC systems, many buildings can experience poor mixing, end-of-branch insulation, or poorly ventilated areas that may require local filtration. It is also important to consider areas that house vulnerable building occupants or visitors. Additional local filtering can be considered at these locations for additional security.

Increase ventilation – HVAC systems are designed for a specific mix of outside air and exhaust air with varying tolerances of those concentrations. This means that if the operator increases the amount of outside air, he can overwhelm the existing heating register and increase the risk of the heat exchanger freezing and causing extensive damage. To avoid extensive damage, equipment failure or a reduction in the life expectancy of the equipment, a technical assessment is recommended before the operation of a system is changed.

Planning and Maintenance – When an HVAC system is operated on a schedule, operators can extend the hours of operation to “purge” the building before and after it is occupied. Operators should also check the condition of the ventilation equipment. Dirt on intake grilles, coils and heat recovery components can significantly reduce airflow. Increasing the uptime of the equipment increases the need and frequency of filter changes and system maintenance and cleaning.

Local Units – Many rooms are equipped with smaller local units that work either alone or in conjunction with other HVAC systems in the building such as fan coil units or chilled beams. These devices do not introduce any outside air and only circulate the room air. Local units with low-capacity filters are not intended for use with high-capacity filters. Certain local units, while introducing outside air, are very similar to FCUs and are fairly common in school classes. UVs are designed to bring in small amounts of outside air to mix with the room’s return air. These devices are typically equipped with a heating coil, filters, and sometimes a cooling coil. Like larger AHUs, these units are not designed to supply 100% outside air in colder temperatures. A change can cause the coils to freeze and result in water damage.

System reviews

HVAC System Assessment – Over a period of years, the operation and performance of a commercial HVAC system can vary significantly from its originally intended design characteristics. If an owner has concerns about the operation of their HVAC systems or is considering changes, they should contact a company skilled in evaluating existing systems and environments before proceeding with changes. The consultancy should examine the condition and operation of the existing systems and evaluate their original designs to determine what improvements could be implemented to increase outside air supply or filter performance. Its professionals should be able to identify deficiencies in existing HVAC systems that can be corrected and what adjustments can be made to improve system performance.

Environmental Assessment – A reputable occupational hygiene consultancy should be used as part of a full environmental assessment to further assess indoor air quality. In addition to viral hazards, a qualified team of air quality scientists can further evaluate mold, dust and other pathogens and pollutants in the air.

Solutions in motion

EFI Global employs air quality experts who work seamlessly with our engineering experts and our customer building teams to provide real-time data with ready-to-read instrumentation and rapid reporting. EFI’s multidisciplinary team of experts has extensive experience and a proven track record in conducting these critical ventilation assessments. They are equipped to document that HVAC systems are working properly and that air quality guidelines are being followed for the health and safety of building users.

From Bo Petersson

Courtesy of Sedgwick


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Disclaimer: publishes independently produced writings by a variety of stakeholders in the compensation industry. The opinions expressed are solely those of the author and do not necessarily reflect those of

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