Performed heating maintenance on Lennox heating system. Ran system through 20 point inspection. Merv filter is dirty, should be replaced. Would recommend replacing full Kit as bulbs on filtration system are burnt out. Air scrubber bulb and catalyst should be replaced as well. Homeowners want to take care of filtration Kit first, and worry about purification Kit later. Need to order replacement kit and return to replace. System is operational upon departure.