Complete 1 system furnace repair and preventative maintenance check. Change filter, check operations and duct system. Find a 10-year-old system operating within manufacture specs, system undersize in the ductwork. The customer has a 3.5-ton cooling system that require 1400 CFM however ductwork only operating at 1000 CFM. Give customer estimate to replace return Plenum, supply Plenum and additional media filter on the outside of the system. Give customer estimate on an air purification system To help improve air quality, Prevent molding and help kill bacteria and viruses.