Transportation modes like school buses and vans create a vector of infection that is often overlooked. “The infection probability in airplanes is similar to the probability in tour coaches and school buses,” thus presenting the opportunity for increased infection rates, especially during longer transit times.
When Steril-Aire ultraviolet germicidal irradiation (UVGI) solutions are placed within the transportation mode’s HVAC system, they will predictably disinfect the cabin air while decreasing maintenance and energy costs of the unit.
“A single control strategy usually cannot provide adequate protection for occupants. It is necessary to integrate multiple strategies.”
There are three-proven solutions for airborne disinfection: Ventilation, Filtration & UVGI.
These solutions are peer-reviewed and supported by the American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE), the U.S. Green Building Council, the U.S. Environmental Protection Agency (EPA) and many others. When these solutions are used together, the disinfection results become more significant and risk is greatly reduced.
For example, in a school bus that has a naturally high rate of air changes per hour, or ACH, (typically 20-50), the effectiveness of Steril-Aire UVGI is greatly increased due to the amount of air that can pass by the UVC solution in the given time. Although the COVID-19 infection probability is not exactly clear, studies have shown school buses to have over 20 times the acceptable risk rate. For most spaces, the infection risk can be reduced to less than 0.1% using the peer-reviewed solutions discussed.
Commonly, HVAC Systems in buildings are often outfitted with UVGI systems to clean coils, disinfect the air and provide energy savings using ASHRAE indoor air quality (IAQ) principles. These principles can be applied to school buses and metro buses as the internal HVAC system is constructed in the same way as a building.
As seen in the study “Innovations Deserving Exploratory Analysis (IDEA) Programs-Ultraviolet Germicidal Irradiation for Transit Buses,” energy savings and IAQ improvements can be accomplished through the installation of UVGI. Below are the main points of this study.
The IDEA Programs-Ultraviolet Germicidal Irradiation for Transit Buses had two main objectives:
- Apply UVGI Systems to Carrier & Thermo King (Trane) HVAC Systems to determine the effectiveness in improving indoor air quality by removing pathogens
- Recognize and quantify the cost savings associated with energy reduction from clean cooling coils and reduced maintenance of bus HVAC systems via UVGI
The application results from this study were similar to IAQ findings of your general building’s HVAC system. Most notably, the testing showed a 99% reduction in common viruses and 95-99% reduction of mold, fungi and bacteria within buses.
By removing these harmful pathogens from buses, one can see less absenteeism from drivers, improved productivity, less overtime, fewer student passenger complaints and other IAQ benefits. While not only creating IAQ benefits, disinfecting HVAC coils will create energy savings that typically offer a return on investment in about 18 months, thus paying for itself in a short time.
The predictable maintenance savings occur in several ways:
- Evaporator maintenance savings
- Reduction of cleaning chemicals and disposal costs
- Fewer air filter & component replacements
- Less out-of-service cost
The Houston Metropolitan Transit Authority calculated the savings from reduced maintenance and estimated cost savings for 100 buses. In today’s dollars, this value would be approximately $180,000 or $1800/bus.
For buses that operate in “non-reheat mode”, there is also a fuel savings. Based upon 100 buses, 300 days of operation and diesel fuel at $5.50 per gallon (average price as of June 2022), the total estimated yearly saving would be $66,000 or $660 per year per bus. IAQ improvements in buses can create sustainable and substantial cost savings for your fleet.
At Steril-Aire, our customers and partners have relied on our expertise in disinfection and IAQ for more than 30 years. In fact, though other companies also have begun offering ultraviolet germicidal irradiation (UVGI) solutions since, Steril-Aire holds the original patent for UVGI disinfection in HVAC applications.
To accomplish the IAQ benefits from UVGI, a best practice is to install an Enhanced UVC Kit from Steril-Aire into your buses. These UVC kits are easy to retrofit into your current HVAC systems and can be powered either by DC or AC power supplies. EUVC Kits come with an IP67 watertight connector and are compatible with any length of Steril-Aire emitters. Steril-Aire emitter life expectancy is about 9000 hours and approximate replacement is one year. Once installed properly, no maintenance is required.
These solutions are a “subtractive” technology as deemed by the U.S. Green Building Council, which means they do not generate ozone and do not add anything back into the air, making the air safer for drivers, students, and the environment.
Download our School/Transportation Guides.
For a free fleet survey, please contact Josh Oelker at joelker@steril-aire.com.
