ProAir’s filtration systems, including the HEPA-6 model (shown here), are designed to deliver up...

ProAir’s filtration systems, including the HEPA-6 model (shown here), are designed to deliver up to 99.99% effectiveness in removing airborne bacteria and viruses.

Photo courtesy ProAir

More than a year into the COVID-19 pandemic, school districts and bus companies are still ramping up their efforts to ensure the safety of students as they head back into the classroom and onto the school bus.

Deep cleaning buses and sanitizing surfaces have become standard practices for most operations, in addition to the use of air filtration technology to eliminate the presence of harmful bacteria and airborne viruses like COVID-19. While the technology continues to undergo developments for the school bus market, operators are increasingly looking to adopt air filtration units as more funding opportunities become available, specifically through the CARES Act and the Consolidated Appropriations Act of 2021.

With more funding and access to the technology, Dave Oberdorff, vice president of sales and business development for ProAir, a supplier of air filtration systems, says operators can restore confidence in their bus drivers and communities as more students get back on the bus.

School Bus Fleet spoke with Oberdorff and a representative from Webasto, another air filtration systems supplier, about their latest offerings for the school bus. They share how the systems work, best practices for use, and how the technology can supplement operators’ daily safety practices.

Filtration for Multiple Vehicle Applications

At the start of the pandemic in March 2020, the engineering team at ProAir went to work on researching how to effectively apply filtration technology to a full-size, 40-foot school bus, according to Oberdorff.

“With about 70% of the COVID virus being spread through the air attached to water particles and the other 30% potentially being spread through contact surfaces, we knew proper air filtration had to be part of the COVID-19 containment solution,” he added.

As part of the company’s research efforts, ProAir looked to the Centers for Disease Control and Prevention (CDC) guidelines on how many air turns per hour were recommended for a hospital room to minimize a viral load of COVID-19. The company also leveraged its experience in supplying the emergency vehicle market with air filtration and purification units utilizing HEPA filters and UV-C germicidal lamps for first responders. Together, these efforts ultimately helped determine the size of the blowers needed for school bus air filtration.

ProAir’s latest filtration systems — the HEPA-3, HEPA-4, and HEPA-6 models — feature high-capacity True HEPA filters that are designed to deliver up to 99.99% effectiveness in removing airborne mold spores, pollen, dust, bacteria, and viruses, including COVID-19, Oberdorff says. Each unit is equipped with a pre-filter to remove larger particulate matter from the air, helping to extend the lifecycle of the filter and allowing it to focus on eliminating the smaller airborne pathogens down to 0.3 microns in size. The ProAir units are also outfitted with germicidal virus killing UV-C lamps, which operate at a 254 nm wavelength for additional air purification.

Since the initial release of the HEPA-6 model, Oberdorff says ProAir has expanded its air filtration product line to include various-sized units to accommodate small vans; Type A, Type C, and Type D school buses; and transit style buses. He also says that the units have served as a great addition for operators looking to supplement their daily COVID-related safety measures, such as surface cleaning and sanitizing buses and requiring riders to wear masks.

“The good thing about the air filtration units is that they safeguard against when someone does come on the vehicle, has their mask down, and coughs — putting contaminants in the air and surrounding surfaces,” Oberdorff says. “Even though you can’t continually wipe down the [buses’] surfaces, you can continue to clean the air while the vehicle is being occupied.”

Equipped with medical-grade HEPA-14 air filtration media, Webasto North America’s HFT 300 system...

Equipped with medical-grade HEPA-14 air filtration media, Webasto North America’s HFT 300 system can eliminate airborne infections and contaminants more than 0.3 microns in size.

Photo courtesy Webasto

High-Volume, High-Pressure Filtration

Operating as a stand-alone system (separate from the vehicle’s HVAC system), Webasto North America’s HFT 300 air filtration system features medical-grade HEPA-14 filtration media and is designed to remove more than 99.995% (0.3 microns or larger) of airborne infections and contaminants like COVID-19.

“The unit moves a very high volume of air at a very high pressure drop,” says Paul Baczewski, Webasto’s national account manager for bus products. “Pressure drop [means] that a high volume of air is entering the filter, but a minimum amount is felt coming out, [so] somebody sitting in front of the filter is not going to feel a tremendous amount of air blowing on them.”

Baczewski adds that both a high volume of air and a high-pressure drop are required to remove a significant amount of viral contaminants, like COVID, in one pass on a school bus. Without a single pass removal, he says, operators could potentially be recirculating contaminated air in their vehicles.

The filter in Webasto’s HFT 300 connects to a 12-volt source and can be mounted in any direction — vertically or horizontally — on a school bus. The system is also equipped with an air pressure monitoring system that can continuously gauge the air flow and condition of the filter. (When a filter replacement is required, Baczewski says a red light will appear on the system, alerting operators.)

“It is estimated in a routine transportation environment that filter life is approximately eight to 10 months,” Baczewski points out. “The manufacturer of [Webasto’s] internal filter, Virgis Filter S.P.A, indicates not to exceed 12 months. Even when the filter requires replacement, the filtration rate remains at a greater than 99.995% level. The air flow level, however, is reduced.”

In November 2020, Prince George County (Va.) Public Schools became one of the first school districts in the state to outfit nearly its entire fleet with Webasto’s air filtration systems. (Prior to COVID, the district operated 119 bus routes, in addition to several bus and car routes for special-needs students.)

“We started researching other public transport apparatuses, like ambulances and fire units, to see how they were approaching things,” says Dustin Nase, the district’s transportation director. “That is how we came across Webasto and their air filtration system and their use inside ambulances.”

Prince George County Public Schools purchased the systems using approximately $60,000 of the district’s CARES Act funding. The systems were installed by the transportation department’s team of mechanics, who were trained by the district’s school bus dealer Sonny Merryman. (By using an in-house team for the installation process, the district experienced about $12,000 in cost savings, according to Nase.)   

Beyond Filtration: Cleaning and Sanitization Solutions

The Zep Assure Program consists of a three-step cleaning and disinfection process for the school...

The Zep Assure Program consists of a three-step cleaning and disinfection process for the school bus.

Photo courtesy Zep

Like ProAir’s Oberdorff mentioned above, air filtration technology, when used in combination with surface cleaning and sanitization practices, can ensure operators cover all bases when it comes to safeguarding against viruses like COVID-19. Below, are some of the latest providers of school bus cleaning and sanitization solutions — ranging from disinfecting lights to spraying and fogging systems.


CleanSpray Technologies provides turnkey solutions to mitigate human exposure to harmful pathogens by cleaning the air and vehicle surfaces. Offering laboratory tested plant-based disinfectants and proprietary delivery systems, CleanSpray seeks to create safe and healthy transportation environments.

CleanSpray’s Automated Spray/Fogging System works on an automatic cycle. With customized installation, the system aims to reduce labor costs and give operators peace of mind.


Grote Industries

Grote Industries’ UV-C disinfecting light for HVAC systems is designed to help public transit and bus companies disinfect circulated air to keep people safe on the road. Grote’s UV-C light assembly installs into the HVAC system’s evaporator compartment, safely functioning during normal bus operations to effectively destroy microorganisms as they pass through the evaporator.


Whiting Systems

The Pure Hard Surface Disinfectant from Whiting Systems is a long-lasting hospital-grade solution designed to keep students and employees safe. The solution can eliminate a variety of bacteria and viruses, including COVID-19, within 30 seconds to two minutes. Bearing the EPA’s lowest toxicity rating, no rinse is required after using the Pure Hard Surface Disinfectant, which can safeguard surfaces up to 24 hours after it is applied.



The Zep Assure Program is an integrated cleaning and disinfection management system. The program follows a three-step process, including cleaning surfaces with a properly diluted solution of Zep Assure Armor Cleaner Concentrate, disinfecting surfaces with Zep Aviation RTU Cleaner Disinfectant or a properly diluted solution of Zep Triton, and coating surfaces with Zep Assure Armor Surface Protectant Pro, an antimicrobial that can treat surfaces for months at a time and through multiple cleanings.

About the author
Sadiah Thompson

Sadiah Thompson

Assistant Editor

Sadiah Thompson is an assistant editor at School Bus Fleet magazine.

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