I hope this helps you, have the repair person check to see if a furnace filter air freshener was installed at your last furnace check up without your knowledge. Also checked all wall and or floor registers to make sure the source of smell is not coming from them, it may be circulating though the duct system.last thing is to replace media pad in humidifier along with furnace filters, if you have air cleaner wash filters with hot water and baking soda, wipe & let dry before re- installing them. Your repair person may have use a strong smelling cleaning solution in humidifier that is now circulating though out your home, good luck.