Deep cleaning vehicles, sanitizing surfaces, and the use of air filtration technology have become standard practices for most, if not all, public transit agencies throughout the pandemic.

Here, METRO spoke with several suppliers of these technologies about their latest offerings for the transit industry — providing insight on how these systems work and how they can help benefit long-term passenger safety. 

ProAir’s HEPA Filtration Models

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 commercial vehicles, according to Dave Oberdorff, the company’s VP, sales and business development.

As part of the company’s research efforts, ProAir looked to guidelines from the Centers for Disease Control and Prevention and leveraged its experience in supplying the emergency vehicle market with air filtration and purification units. Together, these efforts ultimately helped determine the size of the blowers needed for transit and other air filtration applications.

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.

Webasto’s HFT 300

Operating as a stand-alone system (separate from the vehicles 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 in one pass on a 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 bus. The system is also equipped with an air pressure monitoring system that can continuously gauge the air flow and condition of the filter.

NFI Parts PASP System

The Proactive Air and Surface Purification (PASP) system from NFI Parts uses proprietary technology to create advanced purification by producing high-energy clusters, which are distributed throughout the interior of the vehicle. The main goal of the solution is to safely sanitize both the air and surfaces in vehicles without leaving behind any harmful residue. 

“We wanted to provide our customers with a solution that could work for them while their vehicles are in service, and that would be useful beyond the COVID-19 pandemic,” says Brian Dewsnup, president of NFI Parts. “Along with viruses and bacteria, [the PASP system] is effective against mildew, odors, mold, and funguses, ensuring long-term return on investment.”

The solution, which can be mounted directly in the passenger compartment, requires 12-volt power to operate and does not rely on other vehicle systems. It also does not void any vehicle system warranties, and all service components are accessible by removing the system’s cover.

In-service testing of the PASP system has reportedly shown an overall bacteria count reduction of 99.3% and demonstrated the technology’s ability to deactivate the SARS-CoV-2 virus, which causes COVID-19.

Air Cleaning Products from Climate Comfort Technologies

Climate Comfort Technologies' (CCT) line of air cleaning products for U.S. transit vehicles are designed to manage elevated ionized air concentrations within a vehicle’s passenger space.

“CCT products are purpose built for transit applications and components are selected to handle thermal shock, vibration, and variable voltages while minimizing maintenance in comparison to bulb type technologies,” says Scott Imamura, the company’s COO. “While there are clear advantages for air cleaning systems, there is no silver bullet for both surface and air cleaning in transit vehicles. Air cleaning systems should be considered in addition to surface cleaning procedures, as well as the use of A/C air filters in the vehicle.”

As an active air cleaning technology, Imamura says CCT’s solutions can operate within occupied areas without the production of ozone or harmful by-products. Some of the benefits, he adds, include improved capture rates of filter media, suppression of dust, and the ability to help control various odors and inhibit and/or inactivate various pathogens in a vehicle’s air stream.

Three-Stage Air Purification from Knorr Brake Company

Knorr Brake Company (KBC) — a subsidiary of rail and commercial vehicles braking systems supplier Knorr-Bremse — offers a three-stage air filtration and purification solution for use with rail vehicle HVAC systems.

Working closely with the U.S. EPA, KBC has conducted extensive testing prior to and after the system’s release to ensure its efficiency in protecting against viruses like COVID-19, according to Tyler Bowie, KBC’s rail services sales application engineer. He says the antimicrobial system has been tested to be 99.9% effective in removing harmful viruses and bacteria.

The three-stage system starts with the filtration process, incorporating electrostatic discharge to actively target viruses and then uses physical filtration to remove the charged particles and reduce harmful bacteria transmission. The second step involves the Ultraviolet Germicidal Irradiation (UVGI) purification process, in which viruses/bacteria are eradicated with UV-C radiation — without the risk of exposure to passengers. The final step is the disinfection process, which works through bipolar ionization, meaning ions travel through the air and attack pollutants, chemically decomposing them into harmless water and carbon dioxide.

Active Purification from United Safety

United Safety’s Active Air Purification utilizes safe levels of naturally occurring hydrogen peroxide to actively eliminate 99% of viral and bacterial pathogens from air and surfaces, including SARS-CoV-2, which causes COVID-19. This technology improves air quality and safety for ridership and operators while causing no damage to interior surfaces or electronics.