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The Healthy Green Schools & Colleges program advises comparing outdoor air inflow rates to ASHRAE Standard 62.1, which specifies minimum ventilation rates and other measures to provide IAQ that minimizes adverse health effects.
If the comparison shows an HVAC system cannot achieve adequate ventilation and air exchange for the occupancy level, per CDC Ventilation and Childcare Programs guidelines, schools can provide supplemental air systems — for example, standalone HEPA filtration units in all classrooms and assembly areas — according to the standard.
“The solution to pollution is dilution,” Webb says. “With HVAC systems, this involves introducing more outside air and keeping the equipment maintained and operating well.”
Managers must first examine the amount of outdoor air the system brings in. But Webb warns that outdoor air flow standards constantly evolve, making it essential to double-check standards requirements.
“When I started my career, we only needed to produce 7.5 cubic feet per minute of outside air per occupant,” Web says. “By the time I retired, the number had doubled. But even if your current system produces 7.5 cubic feet per minute of outside air per occupant, there are things you can do.”
For instance, technicians can consider changing filters. The Healthy Green Schools & Colleges program recommends using air filters labeled MERV-13 in all HVAC systems.
“You can increase the MERV rating on your filters,” Webb says. “It’s one of the easiest things you can do.”
Webb stresses some equipment will not work well with higher rated MERV filters. A filter well above a MERV-8 rating might tax the equipment.
“The air filter obstructs the airstream, which slows it down and makes the motor work harder to push air through duct work,” Webb says. “Make sure your system can handle the filter you hope to use.”
Porter adds, “Not everyone can swap out their filters and solve the problem.” In those cases, she recommends using the filter with the highest MERV rating possible to help the system operate as effectively as it can.
Technicians also must remember to change filters as required, Webb says. For example, Newport News Public Schools swaps out HVAC filters quarterly in its 70 buildings and 130 mobile classrooms.
“It was a pretty big ask when we went from changing them twice a year to four times a year,” he says. “We had to hire people dedicated to changing filters.”
Other measures include examining the diffuser where air comes out. Is it blocked? Is it dirty? A dirty diffuser just blows dirt into the air.
“A low-cost change is to dust or vacuum these diffusers regularly,” Webb says.
Bipolar ionization can also improve IAQ. This technology, also known as needlepoint bipolar ionization (NPBI), can be installed directly into existing HVAC systems and charges particles to clean the air. The charged particles neutralize particles that contain bacteria, odors and (volatile organic compounds (VOCs) to make it safer and healthier for building occupants to breathe.
Managers can also have technicians install ultraviolet-C (UV-C) fixtures on HVAC systems. These fixtures improve heat exchange efficiency while UV-C light disinfects air as it cycles through return air ducts.
“But with UV-C fixtures, some microbes still get through,” Webb says. “Bipolar ionization addresses the fact that microbes that can impact health are exceedingly small. It imparts an electrical charge into the airstream as it passes through. With an electrical charge on the airstream, it acts like a magnet and gloms together pathogens and creates a bigger molecule that cannot pass through a MERV filter.”
Some improvements, such as cleaning around the condensing unit and doing facility walkthroughs and looking for dirty ceiling tiles, can cost nothing but technician hours.
“If you see dirty ceiling tiles, check the condensing pans,” Thomas says. “Make sure you don’t have leaks or other issues and if you do, repair them quickly.”
Most classrooms also have cabinet unit ventilators, or “consoles that sit against the wall. These ventilators draw air from outside that blows out the top of the unit, where it warms or cools the air to the appropriate temperature,” Webb says. “These cabinets collect dust and need regular cleaning. You not only need to change filters, but you’ve also got to vacuum out these cases. It greatly improves the quality of air coming out the other end.”
When cleaning ventilation cabinets, technicians need to check if anyone has set items on top. Students and teachers often stack books and other things on these ledges, blocking air flow.
“Instead of 8 feet of blowing air, you now have 2-3 feet of air blowing out,” Webb says. “Technicians must ask instructors to remove things from on top and explain why they cannot store items there.”
Managers should examine windows and doors for leaks that might introduce water damage that leads to mold and mildew growth. Webb says it can be difficult to spot signs of mold and mildew in mobile classrooms that have vinyl wallpaper covering the walls, so technicians need to peel back the paper to view the wall.
“Be vigilant for moisture infiltration, whether through the roof, windows or doors,” he says. “These are likely to be your primary transmission points for water.”
The Healthy Green Schools & Colleges program recommends using a computerized maintenance management system (CMMS) for maintenance operations. A CMMS can help managers schedule and record operations and preventive or planned maintenance activities on facility equipment. This software can help managers track HVAC preventive maintenance and maintenance operations.
Installing IoT sensors on HVAC systems also can improve efficiency and operation. These sensors allow technicians to monitor and access HVAC system status in real time, allowing them to make maintenance decisions immediately.
“Automating larger systems in this way lets us monitor HVAC systems for problems and get alerts for specific issues,” Thomas says. “Automating mechanical systems is a tool that helps us understand if we are having problems and respond more quickly when we do.”
Many other tools also can improve IAQ. For instance, an air quality monitoring logger that samples room air and logs its findings. Managers can download and analyze captured data to learn how many parts of carbon dioxide are in that room.
“You don’t want to exceed 900 parts per million of carbon dioxide in a room,” Webb says. “Newport News did this testing monthly, and we tracked the results.”
When testing uncovered regular problems in district classrooms and buildings, Webb says they investigated why.
“Depending on the answer, we’d advocate next steps,” he says. “Sometimes, it was as simple as just cracking the window a bit.”
In other cases, technicians added standalone air cleaners or dehumidifiers to affected classrooms.
“Newport News dealt with mold and mildew,” he says. “We added dehumidifiers because part of what drives mold and mildew is excess humidity. We would drop them into a room until we discovered the cause.”
Cleaning operations do not always fall under the purview of maintenance departments, managers hoping to improve IAQ should pay attention to the way a building gets cleaned, says Aaron Uresti, assistant director for custodial and housekeeping services at the University of California-Riverside.
“Proper floor matting, the right equipment and safe cleaning supplies and chemicals are key initiatives that help improve overall indoor air quality,” he says.
Mats at building entrances prevent contaminants from making their way into the building and eventually into the air. The mats scrape away pollutants as people enter the building.
“Cleaning chemicals also can affect the air you breathe,” Uresti says. “Use products with low-fragrance and low VOCs. Using products with renewable ingredients, such as citric acid, can also help. Floor strippers are among the most potent chemicals we use. Instead of a floor stripper, there are floor pads available that only require a neutral cleaner or water to remove old finish.”
Vacuum cleaners with HEPA filters can prevent releasing contaminants into the air. Cleaners can use automatic floor scrubbers that also vacuum soil, dirt and dust, reducing moisture and dirt inside the building. Cleaners also can use microfiber cloths that effectively remove soil, dust and pathogens from surfaces.
Managers in school districts and institutions of higher learning do not have to break the budget to improve IAQ in buildings. The Healthy Green Schools & Colleges can put managers on their way to implementing low- or no-cost measures that can improve IAQ. Managers can learn more about the new standard and certification program and sign up to participate by visiting healthygreenschools.org.
Ronnie Wendt is a freelance writer based in Waukesha, Wisconsin.
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