Screens are available for inlet and outlet openings in a variety of mesh configurations. Screen mesh sizes are available from 16 mesh X 18 mesh up to and including thrip-resistant mesh in such materials as aluminum, stainless, polyolefin, or fiberglass. Screens are fitted to framework or set in frames as is required for the opening to be screened. Screening of openings reduced chemicals used within the greenhouse. Reduction of insecticide use via a passive insect screening has reduced the entomological issues for all institutional and research greenhouses.