Performed preventative maintenance for 2 high efficiency furnaces per commercial agreement. Both are newer systems installed in 2020. Replaced both air filters with pleated Merv 8 (16x25x1). Tested the heat operation to make sure both start up and run properly. Inspected all the electrical components. Cleaned the burners, flame sensor and burner compartment. Confirmed proper high and low voltages. Performed combustion test on both units. Heater #1 in lobby is operating at 93% efficiency with a CO level of 7ppm. Heater #2 in break room is operating at 93.4% efficiency with a CO level of 9ppm. Both systems are operating properly at this time. No charge due to commercial maintenance agreement. Reme-Halo air purifier “cells” are recommended to be replaced next spring (2023) due to age or when next agreement renewal is due. The cells are recommended by the manufacturer to be replaced every 2-3 years. Even though the cell can still light up past that time frame they get weaker as they get cl