Tips and resources for creating safer work environments when returning HVAC systems back to operation.
Now that states and municipalities across the country are eliminating stay-at-home orders due to COVID-19 – and businesses that had employees working remotely are choosing to return to work – many facilities personnel are concerned about getting their buildings back in operation safely, especially when it comes to their HVAC systems. ASHRAE and the CDC both offer advice on the subject, which we have summarized here.
Prior to a building’s reopening, ASHRAE suggests that facility operators create a strategic plan that includes the following:
- Create measures to make occupants feel safer.
- Ensure a supply chain for critical items, such as filters, as confirmed for delivery.
- Review contractual agreements with tenants with regards to building support.
- Establish a communication protocol with tenants and include key contacts.
- Prepare and provide training for tenants on safety measures.
ASHRAE also offers a number of suggestions concerning building HVAC systems, including:
- Follow the requirements of ASHRAE Standard 188-2018, which has tables to show the typical maintenance on equipment.
- Consider PPE when maintaining ventilation materials, including filters and condensate. Consult additional guidance before duct cleaning.
- Check if all the setbacks and setup modes are reversed back to normal.
- Open outside air intake dampers to their maximum, 100% preferred, four hours minimum, before the reoccupation. The maximum position the outside air dampers may be opened will depend on the time of year, local climate, the temperature and humidity of the outside air, and the capability of the HVAC equipment to condition the outside air so that the system is able to maintain acceptable indoor temperature and humidity. When operating in this “flush out” mode, monitor the system continuously to make sure that unexpected or unacceptable conditions inside do not develop. Upon completion of the flush, the damper positions should be corrected to provide design levels.
- Check to see that space temperature and relative humidity levels are being controlled to the acceptable setpoints.
The CDC also suggests ways to improve building ventilation to help reduce transmission of COVID-19:
- Consider using portable HEPA fan/filtration systems to help enhance air cleaning (especially in higher risk areas).
- Increase the percentage of outdoor air (e.g., using economizer modes of HVAC operations) potentially as high as 100%. (First verify compatibility with HVAC system capabilities for both temperature and humidity control as well as compatibility with outdoor/indoor air quality considerations.)
- Increase total airflow supply to occupied spaces, if possible.
- Disable demand-control ventilation (DCV) controls that reduce air supply based on temperature or occupancy.
- Consider using natural ventilation (i.e., opening windows if possible and safe to do so) to increase outdoor air dilution of indoor air when environmental conditions and building requirements allow.
- Improve central air filtration:
- Increase air filtration to as high as possible without significantly diminishing design airflow.
- Inspect filter housing and racks to ensure appropriate filter fit and check for ways to minimize filter bypass.
- Consider running the building ventilation system even during unoccupied times to maximize dilution ventilation.
- Generate clean-to-less-clean air movement by re-evaluating the positioning of supply and exhaust air diffusers and/or dampers and adjusting zone supply and exhaust flow rates to establish measurable pressure differentials. Have staff work in areas served by “clean” ventilation zones that do not include higher-risk areas such as visitor reception or exercise facilities.
AJ Manufacturing offers a range of products that can help eliminate airborne contaminants in a building’s HVAC system through the use of HEPA and ULPA filtration. Contact us for more information.