Performed water heater and cooling tune up. Checked all major components and system operation. Flushed drain line. Found that 30-day air filter is not sufficient and is allowing evaporator coil and blower to get dirty. This is opening the system up to the potential for biological growth. Recommend chemically cleaning evaporator coil and blower and then applying Teflon treatment to maintain cleanliness. Recommend IAQ 2000 to replace current inadequate air filter and prevent biological growth in system.