When an energy-saving economizer is not used, some outside (fresh) air is still required in almost all applications. A manual hood is the most cost-effective alternative and is simply adjusted one time and remains in place. The setting is usually determined by ASHRAE minimum outside air requirements. Manual hoods are generally good for up to 25% outside air intake.
For carrier 48HC04-06 and 48TC04-09 packaged rooftop unit
MicroMetl Manual Outside Air Intake Hood, 26-13/16 in Length, 11-15/16 in Width