There's a product that you spray into the air ducts that neutralizes mildew and mold in your ducts. You just spray it in the outside air intake at the bottom of your windshield. They are usually below your wipers, you may have to pop the hood to see them. You turn your A/C on high and spray it down the intake vents for about 5 sec. and a 5 sec. shot into the vents in the dash too. Any auto parts store should carry it.