“Clean Air Delivery Rate,” or CADR, the product of efficien- cy and airflow. Effectiveness takes into account how much of the air you’re cleaning. An air cleaner that is 100 percent efficient at cleaning 300 cubic feet per minute (CFM) of air would have a CADR of 300. An air cleaner that is 90 percent efficient at cleaning 1,000 CFM of air would have a CADR of 900 and be three-times as effective. CADR provides you with a metric for comparing various systems. A simple CADR calculator can be found at www.
lumin-air.com. Simply enter the airflow and efficiency of the air cleaner and the CADR is calculated. To put the CADR number in terms people can relate to, the output shows the clean air percentage of a bus’s air conditioning system. It also shows how much airflow that is relative to a typical handheld hair dryer. For example, if you calcu- lated a CADR of 350 CFM, would you feel it was adequate to only clean 10 percent of a 66-passenger bus air con- ditioning airflow? 350 CFM is the airflow of just over four hair dryers. You’d likely want to have many of these smaller systems located throughout the bus. Third: Consider not only the initial purchase cost but the
ongoing cost of anything you install. While your school system can get funds for the initial installation of air cleaning systems on your buses, this is one-time funding. Calculate the ongoing cost of the system. Ask vendors to
include five-year parts warranties, and five years or more of replacement filter changes in their quotes. How do you know when to change filters? As filters load
with dust and contaminants, the pressure drop across them increases, which reduces airflow. Reducing airflow, reduces your CADR, which reduces the effectiveness of your system. The rule of thumb for changing filters is to replace them when the pressure drop across them dou- bles from their initial clean pressure drop. Pressure drop is related to the dust holding capacity of the filter. Filters with high dust holding capacity last longer than filters with low dust holding capacity. You’ll have to replace dirty filters with clean filters based on how quickly they reach their dust holding capacity. So, make sure vendors provide the dust holding capacity of their filters and cost of replacement filters for comparison. While it’s great that school buses are getting the at-
tention and funding they deserve to clean the air inside school buses, it’s important to safely achieve the highest level of disinfection for the least amount of money over the lifespan of the system. ●
Dan Fillenwarth is the president of Lumin-Air.
They need to be back to school. They need to be safe. The answer is clean air.
The Answer is Lumin-Air
The dirtiest air in your school system is in your buses. Lumin-Air has the highest Clean Air Delivery Rate available with low maintenance costs. Our retrofi t improves fi ltration and uses Ultraviolet Germicidal Irradiation (UVGI) as recommended by ASHRAE and the CDC. Learn more at
Lumin-Air.com
Newest Covid-19 Relief Bill Includes Funds for Improvements
to School Bus Ventilation Section 1313 of the Consolidated Appropriations Act of 2021 allows for improvements in air quality in school facilities to minimize the risk of coronavirus disease transmission. Call 866.586.4619
BUDGET CONCERNS? WE WILL WORK WITH YOU. CALL 1.866.586.4619
www.stnonline.com 29
SAFE, CLEAN AIR TO BREATHE
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