A Cost-Effective COVID-19 Indoor Air Program
During the COVID-19 pandemic, the Logan County Health District (LCHD) identified a need in the community for an objective procedure to determine if an indoor space could be utilized by the public and be assured that there was a low risk of spreading COVID-19. Through extensive review of online science-based research articles and journals, an understanding was developed that when outdoors the shedding and spreading of the airborne COVID-19 virus was controlled through social distancing, ultraviolet rays from the sun, and dilution by wind. It was then understood that through adequate ventilation, filtration and purification, indoor air could safely approximate outdoor air and successfully reduce COVID-19 infections. Therefore, an Indoor Air Quality Program was designed that could measure basic parameters of air quality and then incorporate certain strategies and mechanical systems that could reproduce the safe levels of outdoor air in indoor environments.
The COVID-19 virus has been shown to spread through surfaces, droplets and when airborne. It’s been known for years that indoor airborne spread is the most dominant concern for viruses. Droplets are usually large enough (between 20 and 100 microns in size) that they are pulled down by gravity, mitigated by social distancing and readily trapped by facial masks. When the particles are so small that they can become airborne (less than 10 microns) they are called aerosols which is currently agreed upon as the main method of COVID-19 spread. An insightful article published in April 2020 stated that if a vehicle window was opened three inches while the ventilation setting was on “flow through” mode the risk to passengers was reduced by 90% (Allen et al., 2020). That began our understanding of how important simply improving ventilation and controlling indoor contaminants would be to creating an effective educational effort to help our clients of all income levels fight the spread of COVID-19. With that knowledge the LCHD started its Indoor Air Quality Program in July 2020.
Carbon dioxide (CO2) levels indoors have been shown to be a surrogate value for determining the potential for viral spread. A higher level of CO2 corresponds with more stagnant air while a lower value is viewed as “fresher” air. Outside air in Logan County has a CO2 level of around 375 parts per million (ppm). Limiting outside air exchange to a maximum of 10% allows for adequate cooling, heating, and dehumidifying, thereby addressing the issues of cost and comfort. Improving air exchange alone can keep the CO2 level below 1000 ppm but an ideal level is closer to 600 ppm (reducing the CO2 level to below 600 ppm once ended a university tuberculosis outbreak, Miller, 2020). Other ways to improve indoor air quality are to increase the air changes per hour (ACH) by opening windows and doors to the outside. This can be especially effective when using exhaust fans to blow indoor air to the outside, and running the heating, ventilation, and air conditioning (HVAC) fan at the “On” setting instead of “Auto.” An ACH of 3 is considered adequate but above 6 is ideal.
Controlling humidity is also still important because particles around 20 microns in size (those that can contain COVID-19, influenza, and other illness-causing pathogens) when they dry out can shrink in size to the under 10 microns airborne size. Viruses themselves survive longer than bacteria after drying out so keeping humidity around 50% is recommended as a way to decrease spread by reducing their airborne numbers.
When a building’s HVAC system can only provide 3 ACH, additional air exchanges can be accomplished by adding portable room air purifiers that have High-Efficiency Particulate Air (HEPA) rated filtration. Such filters can trap particles down to 0.1 microns in size, effectively removing 99.9% of airborne viruses, bacteria, pollen, and mold spores. Some commercial HVAC systems, if sized large enough to be able to handle the increased air flow resistance of the tighter filters, can replace regular air filters with ones that have a Minimum Efficiency Reporting Value (MERV) of at least 13 for the same effect. Particulate matter (PM) consists of the fine particles that float in the air, most too small to be seen with the naked eye. COVID-19 viruses can attach to particulate matter and be transported via those particles deep into the lungs when inhaled. Particulate matter of 2.5 microns or higher (PM2.5) should be kept below 35 ug/m3 (micrograms per meter cubed) in indoor spaces through filtering and purification.
Besides ventilation and filtration, purification can be incorporated through the inclusion of UV light and ionization. While UV light between 200 to 280 nanometers successfully stops the reproduction of cells, the wavelength of 222 nanometers has been proven to be the safest because it is not absorbed by human skin and especially the eyes. Negatively charged particles (called ions) produced by ionization units are able to combine with positive particles in the air and neutralize them, or if not used will land on surfaces where they are still able to disinfect other particles when they eventually settle out of the air.
Ionization is effective because, unlike UV light bulbs which can be shielded from a pathogen or can dim over time to the point of dropping below an effective level so that they must be replaced annually, ions use the interaction between negatively and positively charged ions. These ions attach to the membrane of the virus causing a chemical reaction rendering them unable to cause infection. They also envelop the virus and puncture the protein spikes on its membrane, neutralizing them by taking away hydrogen. They can also build up around the virus causing it to become large enough to be trapped by air filters. Ozone systems were not recommended due to the potential harmful effects to the lungs if not adequately dispersed before reentering a room after their use.
Meetings were conducted with local HVAC companies to discuss the available information and equipment to improve indoor environments to acceptable ranges. To be able to objectively measure basic indoor air quality and be able to make proper determinations, two affordable air meters were purchased, an Amprobe, Model CO2-100, for CO2 readings and a Langder Technology Color Screen Intelligent Air Detector to measure particulate matter levels. Weekly online meetings were also held with all of the superintendents of the local school districts, the multi-county Career Center and The Chamber of Commerce’s business group. At our suggestion, several schools and food services installed ionization units on their building’s main HVAC systems or placed them inside individual classroom ventilation units. In one room in the first school building tested, with 26 students and all windows closed and a window air conditioner recirculating the room in the air, a CO2 reading of 4400 ppm was recorded! Exercise venues, churches, shops, and retail stores found ways to improve their ACHs such as by purging the air before and after being open and increasing air flow during use. Local businesses were encouraged on the LCHD website to submit applications which were reviewed by LCHD staff Environmental Health Specialists (EHSs) to find ways to improve their indoor air quality levels and safely increase their COVID-19-reduced occupancies.
The LCHD determined that simple preventative measures could adequately improve indoor air quality. Those included installing ionization or UV light, opening doors and windows to introduce outside air, increasing air flow from HVAC units, and upgrading the filters within HVAC units to MERV-13 or HEPA-rated filters. These improvements were implemented in several school districts within the county. One school district even installed high-tech monitors within individual classrooms that altered the air flow through the air handlers based on the CO2 level. With all these preventative measures in place, outbreaks within the school systems in Logan County were minimized and schools remained open for the 2020-2021 school year.
Testing was conducted by the LCHD for CO2 and PM2.5. Concentrations were noted from each monitoring device in individual rooms throughout a various array of businesses, community resource buildings (schools, churches, police stations, fire stations, and senior care facilities), and private businesses. In addition, observations were made in individual rooms to determine what conditions could contribute to higher levels of CO2 and PM2.5 (based on the number of individuals in the room, number of doors and windows and if they were open or closed). Initially, the monitoring devices were placed randomly in the room and data was collected after two to three minutes or when the devices had become acclimated to the conditions. This part of the procedure was evaluated and eventually revised
LCHD data actually showed that open windows in a room full of people could have a lower CO2 level than a room with less people and no open windows. A classroom with 10 students and 2 windows closed had a CO2 level of 1053 ppm. A classroom, two doors down, with between 20-25 students and with one window open had a CO2 level of 553. Particulate matter concentrations did not vary much per room based on the amount of people in the room and whether or not windows or doors were open during the time of testing. In another example, a classroom that had not been utilized at all during the day of testing had an initial CO2 level of 872 ppm. The CO2 monitor was left in the room in the same place and a window was opened. The room was left empty for five minutes and in that time the CO2 level dropped to 720 ppm. The meter was then moved to a seat closer to the open window. It was left again for one minute and the CO2 level dropped to 540 ppm. The same building had an average CO2 level of 997 ppm in rooms that had only closed windows and doors. The same building had an average CO2 level of 701 ppm if a room had at least one window or door open to the outside. An article from Shelly Miller of the University of Colorado at Boulder stated that CO2 levels should be below 600 ppm for a given room (Miller, 2020). LCHD data showed that simply opening a window in a room can greatly decrease the level of CO2 no matter the amount of people in the room. These results were replicated in other buildings as well. Another school building had an average CO2 level of 1221 ppm in rooms with closed windows, and a CO2 level of 665 ppm for rooms with at least one window open.
Providing the schools with this knowledge led to many of the districts opening windows within the classrooms and even on buses, in addition to the other preventative measures that they had introduced. Windows were open for just five minutes at a time when weather conditions were not favorable. Our experience showed that placement of the monitoring devices in each room examined was critical. As expected, placing the device closer to a window resulted in lower concentrations of CO2. Consequently, the procedure was changed to placing the devices away from open windows and vents from the building’s HVAC system, since that skewed data and gave CO2 concentrations lower than what was actually in the room.
Data was analyzed using an excel spreadsheet, where averages were extrapolated from the collected raw data points. This allowed businesses to clearly see how good or bad the air flow was in their given building. This data was then compiled into word documents and sent to each facility where testing was conducted along with each room’s observations. Charts were also created from the raw data in an excel sheet, so a visualization of the data could be portrayed in an easy-to-read format, further strengthening their understanding that indoor air quality is vital in controlling outbreaks of COVID-19.
The program allowed for peace of mind to many of our clients. They are now able to confidently retrofit their existing businesses and schools and also change their behaviors to introduce more fresh air into their indoor spaces. With the easy-to-use but accurate indoor air meters, our office is able to create a baseline level of readings and then return to show the benefits of the actions employed by both public and private entities. Even individual households are able to take advantage of the information we have been able to provide on our website to improve the indoor air quality of their own homes. In addition to the usual recommendations to properly sanitize, wear masks and get vaccinated, much money, time and anxiety has been spared throughout Logan County in fighting against COVID-19 with the startup of our affordable Indoor Air Quality Program. For more information, contact Arie Pequignot, EHSIT at enviro@loganhealthohio.gov or (937) 651-6201. Acknowledgements include Boyd C. Hoddinott, MD, MPH, past Health Commissioner..
Timothy Smith, RESH, MS Director of Environmental Health.
References
Allen, J., Spengler, J., & Corsi, R. (2020, April 22). Is there coronavirus in your car? here's how you can protect yourself. USA Today. Retrieved January 11, 2022, from https://www.usatoday.com/story/opinion/20 20/04/22/coronavirus-car-protect-yourself- column/5166146002/
Miller, S. (2020, August 10). How to use ventilation and air filtration to prevent the spread of coronavirus indoors. The Conversation. Retrieved January 11, 2022, from https://theconversation.com/how-to-use- ventilation-and-air-filtration-to-prevent-the- spread-of-coronavirus-indoors-143732
Links to Other Indoor Air Articles