Your furnace may not have a fresh air intake at all. However, some systems do have provisions for fresh air intake, either a fresh air duct and cycle timer, or some sort of ERV. Also possibly a whole-house dehumidifier with a fresh air intake.
Fresh air intakes are required by law in some places but older houses sometimes don’t have them. An HRV or ERV is best for ventilation. If you want “free” cooling then the recommendation is to use an air exchange. If you don’t have an air exchange, we have Honeywell air exchangers such as the one seen below.