Protected production offers enhanced control over environmental conditions, optimizing vegetable productivity and resource efficiency. Carbon dioxide (CO2) serves as the main substrate for the production of carbohydrates, influencing plant biomass, yield, and nutritional quality. However, the intensive uptake by crops and relatively airtight conditions universally lead to CO2 deficiency in protected production facilities. Elevated CO2 has multifaceted effects on C3 crops, including improved photosynthesis, altered metabolic activities, reduced stomatal conductance, and enhanced resistance to most biotic and abiotic stresses. The understanding of these mechanisms is crucial for developing strategies to optimize crop productivity and improve stress tolerance in protected vegetable production. To supplement sufficient CO2 to vegetables grown in protected production, various techniques have been applied to enrich the CO2 levels in protected production. However, traditional CO2 enrichment techniques have longstanding disadvantages of relatively high cost, low energy efficiency, and increased CO2 generation. Thus, exploring innovative CO2 enrichment techniques could contribute to a circular carbon economy and mitigate greenhouse gas emissions.