The Centers for Disease Control and Prevention recently updated guidance to acknowledge that COVID-19 is primarily being spread through the air we breathe. While research has indicated as much for quite some time, the formal recognition of the primacy of airborne transmission means that the focus for safety guidelines has shifted from cleaning surfaces to improving ventilation.
In acknowledgement of the important role mechanical ventilation plays in reducing the risk of COVID-19 transmission, the American Society of Heating, Refrigeration and Air-Conditioning Engineers (ASHRAE) issued recommendations in January on air filtration and cleaning and using ventilation systems to optimize air exchange rate. But, as with so many vulnerabilities exposed by the pandemic, this underscores the need for broad and lasting changes.
As part of its effort to update ventilation standards – the guidelines and best-practices that inform our building codes — with knowledge gleaned from the COVID-19 pandemic, ASHRAE is reexamining its standard for measuring air-exchange effectiveness in buildings and it has solicited guidance from Drexel civil engineering professor L. James Lo, PhD, who will join a group of engineering and public health experts to develop and approve changes to the standard.
Lo, who has been helping the public understand the role ventilation plays in indoor air quality and mitigating COVID-19 transmission throughout the pandemic, recently provided the Drexel News Blog with insight on how ASHRAE arrived at its current ventilation standard and how it will approach the big changes that lie ahead.
Ventilation standards are guidelines and best-practices that are often used to develop building codes and operating procedures. ASHRAE’s Standard 62.1, called “Ventilation for Acceptable Indoor Air Quality,” and 129 “Measuring Air Change Effectiveness,” are the primary U.S. guidelines that addresses ventilation and air exchange indoors. Lo notes that the standards have historically coalesced around maintaining indoor comfort and the perception of cleanliness. In recent decades health and energy use considerations have also led to changes in the guidelines.
But much like how the great Chicago fire of 1871 led to many building safety standards still in use today, Lo expects the new ASHRAE standards to take a broader look at indoor air management as an essential factor for maintaining public health.
What new information will likely be considered in discussions about updating the standards?
Standard 62.1 (Ventilation for Acceptable Indoor Air Quality) might be updated with design considerations for pandemic operations, while Standard 129 (Measuring Air Change Effectiveness) needs to be updated to allow such designs. Currently, Standard 129 is largely performance-based by measurement, which is difficult for engineers to specifically design the air distribution indoors.
What are some ways building managers/engineers are currently testing and monitoring their ventilation systems to ensure they are reaching current performance recommendations?
Both occupancy sensing and carbon-dioxide concentration monitoring has been used. The recommendations have always assumed a particular occupancy scenario for a given space, if that is breached, the recommendations are not particularly effective.
Could we see new ventilation certifications emerge as a result of the pandemic?
Yes, especially ones to help the public to decide which building or location is safer. Whether such certification has a long-term effect remains to be seen, but we are currently seeing some efforts to create “healthy building” certificates, similar to “energy efficiency” or building sustainability certifications such as Leadership in Energy and Environmental Design (LEED).
What sorts of things should people pay attention to if they have to enter a space in which they are uncertain about its level of ventilation, that might signal whether it is safe or not?
Ventilation is certainly something that is going to be more on people’s minds as we begin to return to shared indoor spaces, but it’s a tricky thing to see or feel.
One simple thing to keep in mind is occupancy. By now many spaces have a designated occupancy limit or have been adjusted to ensure that only a certain number of people can be inside. If you are in a place where it isn’t well marked to limit occupancy or ensure distancing, then you might be more careful about entering or how much time you spend inside.
You can also take note if windows and doors are open, to promote maximum air exchange, or if there are portable air purification units. And at this point, if you are in a place that feels stuffy, it is probably not well ventilated.
What are some things that might limit a building or a space from being able to reach a ventilation standard?
All of our commercial HVAC equipment in buildings has been designed with a much smaller outdoor air intake in mind (approximately 0.5 to 1 air change per hour) to provide the minimal ventilation specified by ASHRAE 62.1. So if we simply ask people to “bring more outdoor air in for ventilation,” the equipment will not be able to handle the additional load for heating and cooling. This means that any new recommendation would need to provide practical guidance in support of the theory that more air exchanges will help to mitigate transmission of the virus.
It is also important to note that most residential systems do not have ventilation air, they rely on regular opening of doors and windows and natural air penetration from outside to exchange indoor air. Some states are exploring requiring dedicated ventilation systems, that bring in outdoor air, for all new construction – but this is far from being a widespread practice.
What do you see as some of the biggest challenges for setting a new standard?
For Standard 62.1, the energy impact vs. ventilation has always been the most difficult balancing act. As the pandemic fades and energy efficiency comes more into focus again, people will once again question the need and effectiveness of a larger ventilation rate and the costly systems that are required.
For Standard 129, it is very difficult to predict how airflow would move inside a building considering all the variables, hence the difficulty in assessing its performance without measurement. This would impact the definition of the “effectiveness” a ventilation system has and we will need to work for a long time to determine how an engineer can access such goal in his/her design.
How is ASHRAE incorporating public health input for the COVID-19 revision of 129?
There is a ASHRAE committee entirely focused on environmental health, so we will be in regular communication with them to ensure their insight is included in Standard 129.
What is some of the most useful research you’ve seen so far related to ventilation and airborne spread of COVID-19 that might help to guide the 129 revision discussions you will be part of?
Visualization tools for indoor air distribution have been very informative for both decision-makers and the general public. We all saw the animation video of how airborne particles can travel a lot further than 6 feet. Things like that are what helps to open the eyes of policymakers and the general public.
How does the standard-revision process work? What kind of timetable are you looking at for finalizing it?
Standard revision is a long-term project which typically lasts 2-4 years. We open it up to a lot of public commentary and must address all of those comments. Most comments or requests to change generally come from the HVAC industry practitioners. Their concerns on the practicality usually have merits in terms of implementation of the standards. Any standard will have multiple voting phases as well, and a lot of transparency, and that’s why the timeline is a bit longer. We believe the revised Standard 129 should be published in 2024.
Lo is an assistant professor in Drexel’s College of Engineering and director of the Building Autonomy and Simulation Lab in the Department of Civil, Architectural and Environmental Engineering. He has been interviewed about building ventilation during the COVID-19 pandemic by a number of news outlets, including Insider, The Washington Post, and NBC News.
Media interested in speaking with Lo should contact Assistant Director of Media Relations Britt Faulstick at bef29@drexel.edu or 215.895.2617.
