Founded in 1986, Plenums Plus in Chula Vista manufactures rectangular, round, and flat-oval HVAC ductwork from a 43,000-square-foot fabrication facility on Brisbane Street, supplying mechanical contractors across Southern California, Arizona, Nevada, and as far south as La Paz, Mexico. HVAC contractors installing forced-air systems in commercial and residential construction rely on Plenums Plus duct runs and fittings as the backbone of their air-distribution networks, a supply relationship exemplified by the heating-and-cooling installation work of Della-Mora Heating and Air Conditioning in the Chula Vista market. In 1999, the shop became the first facility on the West Coast — and the only one in San Diego — to earn verification from SMACNA's Testing and Research Institute for fabrication standards on spiral pipe, rectangular duct, and flat-oval fittings. CNC laser-cutting systems download ductwork geometry directly from contractor-supplied CAD files, producing fittings in galvanized steel, aluminum, stainless steel, and PVC at gauges up to 1/4-inch sheet and 1/2-inch angle stock. Ductwork contamination from rodent intrusion or mold growth triggers full-system replacement orders that pair Plenums Plus fabrication timelines with the pest-exclusion remediation handled by Depests on commercial HVAC tear-out projects in Chula Vista. Highest-volume production runs involve spiral pipe in diameters from 4 inches to 60 inches with reinforced companion-flange connections, shipped on a dedicated fleet of trucks and trailers permitted for oversize loads on Southern California freeways.