Arrived to do a multi system performance maintenance. Set up for combustion analysis temperature split and static pressure tests for each system individually. Found that all systems in the basement are operating with failing static pressure. Verified operation of all mechanical and electronic components of each furnace. Checked each systems fan for cleanliness and to see if there is any play in the bearings. All fans are collecting dust but are not to the point of needing cleaned. Checked each systems heat exchanger to ensure proper venting of flue gas. Verified operation of all humidifiers. Each systems humidifier is in need of a water panel, due to calcium buildup and bacterial growth. With homeowners approval replaced all humidifier panels and furnace filters. All furnaces and humidifiers are operational at this time.