All plants for the process of photosynthesis require sunlight, water and carbon dioxide - CO2.
O + Light → C6
In other words, if CO2 level is enough, plants grow faster. Beside the photosynthesis, plants breath all their life (since they start growing till harvest). At day time plants absorb CO2 and release it via foliage stomata together with oxygen (O2). At night time plants release only CO2 (no photosynthesis).
Because of drought stomata close and plants stop to absorb CO2. Hydroponic method of growing provides plants with water all the time, so plants constantly absorb CO2 and grow without stopping! City atmosphere contains about 400ppm of CO2, and plants are able to use about 1000ppm of CO2. Thus if the air in a greenhouse is not renewed, maximum plant growth is not possible.
The best solution to control CO2 in a greenhouse is Sensiroom CO2
. This is a controller that constantly checks and maintains an optimal for plants CO2 level. This is the best way to control CO2 level in a greenhouse. It is recommended to place a bottle with CO2 far from a vent (it is better to turn off ventilation when the greenhouse air is enriched with CO2).
Warning! CO2 is dangerous for people! Use CO2 in a greenhouse when no one is there.