Service call completed, client have a persistent smell problem when cold air is on the unit but not when is on heating mode, visually inspect unit # 1 and #2 airhandel coil, smell no actively present directly from coil, proceed and clean coil with cleaner and peroxide, rinse coils and turn on system, the smell still present fron the supply duct vent, this is a new house construction, system insby other company, they replace the evaporate coil and the smell problem still presented, providing with options that might eliminate or prevented to spread the bacteria that is causing the bad smell on the home