Identify the opening’s purpose
DASMA separates ventilation for air movement from openings intended for floodwater. Do not assume a grille satisfies both functions. Bring existing plans or equipment information to the designer or qualified professional responsible for that requirement.
Do not order a solid door and improvise later
Adding holes can affect the door’s construction and performance. Resolve a manufacturer-supported configuration before ordering, including whether its approval documents apply to the requested openings. Ask the project team to coordinate the door specification with any building or mechanical requirements.
Put responsibilities into the proposal
A useful quote identifies who confirms the required opening, who specifies its location and what documentation accompanies the door. If the current purpose remains unknown, list it as an unresolved design question. That is more useful than an assurance that a standard grille will work everywhere.
Your questions
Can I cover a vent to keep insects out?
Do not block an opening until its purpose has been established. Ask the responsible professional about a compatible screen or other solution that preserves its required function.
Can the installer cut vents into any new section?
Do not assume that is permitted. The manufacturer and project requirements need to support the alteration and the resulting assembly.