Life After COVID-19: How Our Experts View HVAC Design Systems and Contaminants in a Coronavirus World
The COVID-19 pandemic forced us to evaluate many of the often-overlooked facets of life. Our attention turned to the surfaces we touch, the cleaning products we use, and even the air we breathe.
Masks became as routine as wallets and car keys. And every building owner or manager rightfully sought to transform their schools, grocery stores, banks, and office buildings into socially distanced spaces that rivaled hospitals in their cleanliness.
As more about COVID-19 and its spread became known throughout 2020, particularly the distance airborne “droplets” can travel between persons, questions arose around how facilities’ air quality could be improved and how HVAC systems could be part of protecting the health of those inside. How we considered the role HVAC systems played turned from a matter of maintaining others’ comfort to a matter of preserving others’ health. And HVAC systems themselves became a key player in the fight against the spread of COVID-19.
Tri-Tech has been asked, as a design team providing mechanical-engineering services, to provide opinions and recommendations for multiple clients on how facility HVAC systems can have an impact on the spread of viruses, such as COVID-19. So, we wanted to address ways an HVAC-system design and related air-ventilation products could help address COVID-19-related concerns.
While much of the specific data related to air-ventilation products as of late has yet to be corroborated, we can help you consider what may be the most appropriate utilization for your facility.
HVAC-System Strategies for Airborne Contaminants
There are three strategies associated with HVAC-system designs and installation methods that deal with airborne contaminants, such as the SARS-CoV-2 virus, the virus that causes COVID-19: contain, remove, or attack.
Containment
Hospitals generally look to contain contaminants. Hospital buildings’ HVAC systems are designed specifically to address particular containment strategies for different spaces using positive and negative pressurization. Space pressurization defines the relationship between airflow into and out of a space and the adjacent spaces. If a space is positively pressurized, airflow supply within the space will exceed airflow leaving the space through return or exhaust systems. This causes excess supply air to leak out of the space into surrounding spaces. Similarly, negative pressurization of a space will cause air leakage to flow from surrounding spaces into the negative space. Patient rooms are negatively pressurized, helping reduce the chance of airborne contaminants escaping. Operating rooms are positively pressured to keep contaminants out. These strategies are also used in hospital restrooms and stairwells. Containment of contaminants works best in a structure, like hospitals, designed and built with spaces used for vastly different tasks. Leveraging the same strategy in an office building or residence facility would prove more difficult due to the differences in building infrastructure systems and space layouts.
Removal
Ideally, HVAC-system designs would remove contaminants from the air in a building. But it is not that easy or straight forward. Heavier contaminants or those attached to heavy particles complicate removal strategies. Contaminants may fall out of the air, landing on surfaces where they tend to get covered by dust, soil, or equipment. To remove those contaminants that do move well through the air, a facility’s HVAC equipment would need to remove air directly from the source before it circulates to other people who may be sharing the space.
In most facilities, air is mixed between multiple spaces. And because viruses, such as SARS-CoV-2, are passed from person to person, the potential source(s) exists throughout a facility. For removal to prove effective, a building’s HVAC system would need to exhaust the air at a rate commensurate with any contaminants’ generation and spread. Removal, then, can be considered a potential strategy for facilities, but for it to prove effective, it will likely require extensive budgeting beyond what other strategies may necessitate to install and maintain equipment and its functionality.
In 2020, the American Society for Heating, Refrigeration, and Air-Conditioning Engineers (ASHRAE) did recommend increasing outside air as part of a facility ventilation strategy. And while it may buttress a ventilation strategy centered on removal of inside air, increasing outside air can negatively affect the efficiency and performance of a facility’s mechanical equipment by requiring additional heating or cooling to treat the additional outside air. So, should removal be considered for your facility? While increasing ventilation to a facility may not be the best method of eliminating airborne contaminants, Tri-Tech MEP engineer Roger Butler says, “It is hard to tell what the impact will be right now, but we know it isn’t a step in a wrong direction.”
Attack
Perhaps the most popular of the three strategies, particularly for HVAC system designs for office buildings and similar facilities, is to incorporate devices that attack airborne contaminants. In 2020, the market expanded offering more of these kinds of devices, and they range in their effectiveness. Some of the newer products in the last nine months have promised wholesale solutions, eliminating airborne contaminants from the source, but there is no data substantiating their effectiveness. So, what has worked?
For decades, ultraviolet (UV) lights have proven effective in killing many kinds of bacteria, helping prevent mold growth and dealing with viruses. UV lights use radiation to destroy the outer protein coating of viruses, including the SARS Coronavirus, which is different from the virus that causes COVID-19.[1] UV lights require direct contact with bacteria and viruses to be effective. To ensure their effective placement, these lights often go into ductwork near cooling coils. If UV lights are not placed where they have direct proximity to viruses, their effectiveness is diminished. This is why their use against viruses on surfaces, which can be covered by dust or other contaminants, fails to prove as effective against viruses that are airborne.
Installing UV lights in ductwork is also the safest way to use them. Improper installation of UV lights in person-occupied rooms can lead to injury.[2]
Although using UV lights is time-tested and effective against many kinds of bacteria, it has limitations. Because of their location within ductwork, UV lights can attack only those contaminants in the return air, but many contaminants (such as viruses) need to be exposed to UV light for about ten seconds to be killed. In other words, UV lights work to attack viruses, but the contact time required for them to be effective is often too long, or the light’s intensity is too low. “When you do the math,” says Tri-Tech MEP engineer Ben Florkey, “you find that to kill something in the air would require you to not only place them at the coils but to line the next fifty to one hundred feet of duct with UV lights. This isn’t practical.”
Also, while UV lights are effective at killing bacteria and mold, it is not yet clear that they are as effective against the virus that causes COVID-19. As more data is collected on the effectiveness of UV lights specifically against the virus that causes COVID-19, those who already have properly installed UV-light systems in their ductwork should ask Tri-Tech Engineering for a referral to an HVAC technician who can ensure their current systems are properly functioning to terminate other airborne containments and bacteria.
Some “attack” products generate and populate the air with hydrogen peroxide (H2O2) molecules. These products provide the advantage of attacking contaminants where they are generated and where they may remain. This includes any heavier particles that dwell on surfaces or linger in the air. The setback H2O2 poses is that it can be an irritant. The Occupational Safety and Home Administration (OHSA) recommends an H2O2 air concentration limit of 1 part per million. Meanwhile, researchers at the University of Saskatchewan (Canada) have found that mopping a floor with H2O2-based disinfectants can result in an air concentration of 0.6 parts per million.[3] So, although there may be room to experiment, an H2O2-based “attack” strategy is a risky proposition for schools and other facilities.
The remaining solution—and the one we recommend among those mentioned—is known as needlepoint bipolar ionization (NPBI).
What Is Needlepoint Bipolar Ionization (NPBI)?
NPBI products produce ions that capture gaseous particles and contaminants, including volatile organic compounds (VOCs). Through a process of ionization, NPBI units give positive charges and negative charges, respectively, to participles in the air, which is why it is called “bipolar.” “Needlepoint” refers to how the ionization comes from the end of two electrodes that react with water vapor and oxygen, creating free radical ions These ions improve air quality by killing contaminants and breaking down odors.
Unlike with H2O2, there is no need for concern about having too high a concentration of ions. Ions occur naturally in nature, regulating and breaking down harmful substances. NPBI products today avoid the problems caused by older ionization devices, which generate ozone, an irritant and potential carcinogenic.
An NPBI unit sits in an HVAC unit or ductwork, spreading positive and negative ions into a space. Bipolar ionization has been proven to be effective at reducing the concentration of airborne contaminants, including the COVID-19 virus. This effectiveness is borne out by acceptance of building code standards that allow NPBI units to qualify for enhanced filtration exceptions, which reduce required outside air volumes in spaces utilizing NPBI units. These units help address contaminants at the source and help save costs by reducing the required amount of outside air, potentially saving thousands of dollars on chiller equipment costs and reducing energy consumption.[4] NPBI products are scalable and can be used in the smallest furnace or fan coil unit to the largest air handling units.
NPBIs also reduce the number of smaller particles in the air by causing them to join together, making them large enough to be captured in air filters. This provides the advantage of allowing the filters to be more effective. But it does lead to one potential setback. “One disadvantage,” says Tri-Tech MEP engineer Samuel Thompson, “is that buildings treated with NPBI may have to replace air filters more often or see more dust on surfaces.” This latter effect is most noticeable initially but less so as time goes on. While purchasing more filters may be an additional cost, they won’t counter the savings associated with leveraging NPBI. In other words, NPBI units allow for better air quality and better savings.
NPBI units can be used in residential systems or in the largest of air-handling units. And they are typically self-cleaning.
NPBI units warrant one note of caution. Devices that produce ions have the potential to produce ozone, or trioxygen (O3). O3 is listed by the OHSA as an irritant and has an OSHA permissible exposure limit of just 0.1 parts per million.[5] Any device, then, being considered for use any human-occupied space should be listed by Underwriters Laboratories (UL) as not producing O3.
Life Beyond COVID-19
COVID-19 elevated many mundane, overlooked facets of life into the realm of strategic decision-making: Does this mask protect me and my team members from airborne droplets? Have I washed my hands enough? Are people standing or working far enough apart?
And the cleanliness of the air, particularly indoors, became one of them. As we help clients navigate life and facility needs shaped by COVID-19, we know one day COVID-19 will no longer force building owners and managers to make the kinds of decisions they are making today. Even so, we advise all building owners to maintain this new normal of considering the role a facility’s HVAC system plays in preserving and maintaining the health of all those inside.
We’re here to help clients discern and decide on the system and subsequent equipment that is best for their budgets, their facilities, and those inside them.
Call Tri-Tech Engineering today for more information.
[1] U.S. Food and Drug Administration, “UV Lights and Lamps: Ultraviolet-C Radiation, Disinfection, and Coronavirus,” fda.org. Accessed on January 12, 2021.
[2] Ibid.
[3] University of Saskatchewan, “Bleach-alternative COVID-19 surface disinfectants may pollute indoor air, research shows,” MedicalXpress.com, December 2020, https://medicalxpress.com/news/2020-12-bleach-alternative-covid-surface-disinfectants-pollute.html#
[4] “Needlepoint Bipolar Ionization Case Studies,” Purge Virus, accessed February 16, 2021, https://purgevirus.com/bipolar-ionization-case-study-highlights/.
[5] Curtis Nipp, “Safety Data Sheet for Ozone,” CB&I, July 1, 2014, https://www.jondon.com/media/pdf/msds_docs/MS-OE-SONOZ.pdf#