Identify the purpose of the proposed opening
An air-ventilation request, a mechanical-system requirement and a flood-opening design are different matters. Tell the relevant designer or contractor which problem the project is meant to solve. A hot garage is not enough information to select a vent size or position, and a screen should not be assumed to perform a flood-opening function.
Check the effect on the door
DASMA cautions that vent openings can affect structural capability, operation and thermal performance. Ask the door manufacturer about the proposed configuration before any alteration. The required documentation may depend on the building and product; a vent that fits physically is not thereby an approved modification.
Coordinate the responsible specialists
When a building ventilation or flood design requires professional input, settle that scope alongside the door selection. The final door order should identify the agreed factory or approved configuration. Keep the relevant design and product records together so a later replacement does not silently remove a required feature.
Your questions
Can an installer simply cut a vent in an existing section?
The manufacturer and applicable design requirements need to be checked first. Cutting can change the assembly’s performance and is not merely a cosmetic change.
Is a garage door vent a guarantee of safe air quality?
No. Ventilation design depends on the space and its use. Follow the responsible professional’s requirements rather than treating a door accessory as a complete solution.