How long does a CO₂ bag last? A CO₂ bag constantly releases CO₂ for around 4-6 weeks, depending on the temperature and air circulation. How much CO₂ is optimal for plants in the grow box? The ideal CO₂ value is 800-1,200 ppm. Plants grow much more vigorously in this range than in normal room air (approx. 400 ppm). In which growth phase is CO₂ [...]