Performed a complete heating 2 system maintenance and inspection. 2016 Gas systems. Inspected and tested all electrical components and safety controls on the indoor unit; all components tested within manufacturer specifications. Verified system temperatures: return air temperature measured at 71°F; supply air temperature measured at 113°F and rising. Confirmed air filter was recently replaced by client; filter size is 20” x 25” x 4”. I visually inspected the outdoor unit, The outdoor unit was in good condition . Provided estimates for surge protection. Client would like to visit in the spring. Client would like estimate to add a humidifier into the downstairs system. Confirmed system was operating properly and heating upon departure.