I arrived at our clients home for a 2 system maintenance inspection. Our client provided new air filters to be replaced today. On e the filters were replaced I proceed to clean and test both furnaces. I cleaned the flame sensors, pressure switch ports and ensured the fire shutoff safeties were all working properly. All motors were testing within manufacture specifications today. While preforming the gas leak test I did find the upstairs unit to have a small gas leak at one of the union fittings. I showed a video to our client and we addressed it immediately. We also spoke about air purification for both units and I sent over an estimate for 2 Air Scrubber systems. Both units passed todays inspection and are ready for remainder of winter.