Ask an expert on Coronavirus: Sunondo Roy shares engineering guidance
Sunondo Roy provided expert advice to engineers and others involved in the technical aspects of engineering and designing building systems
Consulting-Specifying Engineer sat down virtually to ask engineers and building experts how COVID-19 was affecting the technical and engineering aspects of their jobs. Hear from Sunondo Roy, PE, LEED AP, Vice President, CCJM Engineers Ltd., Chicago.
Question: Have building owners or clients approached you to assist with changes or updates to their building to help protect against COVID-19?
Roy: No, we have not been approached. We have been monitoring the Centers for Disease Control and Prevention website for any guidance on transmission through ventilation systems. We could find only two references to ventilation systems. One was for infection control on commercial ships (e.g., cruise ships) that indicated no need to sanitize or scrub down ventilation systems in ships. A second was a tangential reference in Interim Infection Prevention and Control Recommendations for Patients with Suspected or Confirmed Coronavirus Disease 2019 (COVID-19) in Healthcare Settings.
This guideline indicates under Section 7:
Implement Engineering Controls
Design and install engineering controls to reduce or eliminate exposures by shielding health care providers and other patients from infected individuals. Examples of engineering controls include:
- Physical barriers or partitions to guide patients through triage areas.
- Curtains between patients in shared areas.
- Air handling systems (with appropriate directionality, filtration, exchange rate, etc.) that are installed and properly maintained.
Question: What test-and-balance or air balancing challenges have you encountered? What unique challenges are you solving?
Roy: None related to COVID-19.
Question: What advice would you offer for building owners to enhance indoor air quality or indoor environmental quality overall?
Roy: According to the Centers for Disease Control and Prevention website, the SARS-CoV-2 virus and its resulting COVID-19 disease spreads person-to-person through aerosol droplets expelled through coughing and sneezing, the droplets are fairly large and tend to land on people and surfaces within 6 feet of the source. The droplets can also be inhaled within that same 6-foot distance.
As such, there appears to be fairly low probability of entrainment into the building air conditioning system. None of the Centers for Disease Control and Prevention literature indicates the survivability of the virus in ductwork and air handling systems. However, since the primary means of transmission is by contact of aerosol droplets to the nose or mouth or inhalation, it seems unlikely that the virus can spread through the myriad turns and obstructions within an air handling system of ducts, coils, filters and dampers.
According to another study Effects of Air Temperature and Relative Humidity on Coronavirus Survival on Surfaces, published in 2010 in the journal Applied and Environmental Microbiology, once the droplets settle, it does not appear the virus can re-entrain into the airstream as a dry particle and survive. The study also indicates the virus survivability decreases with increasing temperature above 20°C (68°F) and relative humidity between 20% and 80% with greatest inactivation at 55% RH. The surface survivability ranged from over 28 days at 4°C (39°F) and 20% RH to as short as 3 to 5 days at 20°C (68°F) and 55% RH. At 40°C (104°F), the virus survived from 120 hours at 20% RH to 12 to 24 hours at 55% RH and only six hours at 80% RH.
Some ultraviolet filtration manufacturer websites are already claiming to offer COVID-19 infection mitigation in HVAC systems although there’s no proof of the virus being entrained in ventilation systems nor whether they have any proof whether UVC lighting (ultraviolet light with wavelengths 200 to 280 nanometers), which has been shown effective to inactivate the conventional seasonal flu virus (Influenza A, H1N1 is the most common) in lab tests is as effective against the SARS-CoV-2 virus in air handling units.
The first advice to building owners is not to panic with infrastructure changes for the virus du jour in the news. Every few years, there is a new coronavirus (e.g., SARS, MERS, now COVID-19) that is spreading regionally or globally. Each pathogen has particular transmission properties that may or may not be affected by the building ventilation and comfort conditioning systems.
Rather, building owners will be best served to ensure their equipment is well maintained, operating to provide ventilation in compliance with ASHRAE 62.1-2019: The Standards for Ventilation and Indoor Air Quality to all tenants and common areas and maintaining proper air movement, temperature and humidity levels in compliance with ASHRAE 55-2017: Thermal Environmental Conditions for Human Occupancy.
Question: Describe a unique health care project in which COVID-19 patients might be treated. This might be a hospital with specialty infectious disease coverage.
Roy: No direct recent project experience. However the following is instructive.
From the Centers for Disease Control and Prevention website, the following provides guidance in Healthcare Facilities: Interim Infection Prevention and Control Recommendations for Patients with Suspected or Confirmed Coronavirus Disease 2019 (COVID-19) in Healthcare Settings. Of interest to HVAC professionals is section 4:
Take Precautions When Performing Aerosol-Generating Procedures
Some procedures performed on patient with known or suspected COVID-19 could generate infectious aerosols. In particular, procedures that are likely to induce coughing (e.g., sputum induction, open suctioning of airways) should be performed cautiously and avoided if possible.
If performed, the following should occur:
- Health care provider in the room should wear an N95 or higher-level respirator, eye protection, gloves and a gown.
- The number of health care providers present during the procedure should be limited to only those essential for patient care and procedure support. Visitors should not be present for the procedure.
- Aerosol-generating procedures should ideally take place in an airborne infection isolation room.
- Clean and disinfect procedure room surfaces promptly as described in the section on environmental infection control below.
Elsewhere on that same page, Appendix: Additional Information about Airborne Infection Isolation Rooms, Respirators and Facemasks:
Information about airborne infection isolation rooms:
- Airborne infection isolation rooms are single-patient rooms at negative pressure relative to the surrounding areas and with a minimum of 6 air changes per hour (12 air changes per hour are recommended for new construction or renovation).
- Air from these rooms should be exhausted directly to the outside or be filtered through a high-efficiency particulate air filter directly before recirculation.
- Room doors should be kept closed except when entering or leaving the room and entry and exit should be minimized.
- Facilities should monitor and document the proper negative-pressure function of these rooms.
Question: What might other engineers/building professionals need to know when tackling COVID-19 projects?
Roy: At present, there are no COVID-19 projects nor should there be. Until the transmission modalities for this and other novel coronaviruses are established with respect to building ventilation systems through the Centers for Disease Control and Prevention, National Institutes of Health or other such competent agencies or affiliates, any claims to “solve” a problem that doesn’t exist is simply fearmongering and opportunism and contrary to the professional engineer code of ethics.