Carbon dioxide benefits plants in restricted indoor growing areas. Plants will deplete carbon dioxide levels in an indoor environment over time. The present invention provides a process design, system, and apparatus for a controlled, non-electrical, non-heat generating, non-mechanical, production source of CO2. The source of CO2 is fungi inoculated into a scientifically sterilized, enclosed growth medium prepared in a laboratory setting. The fungi is provided with an optimum food source from which the fungi may produce CO2 for at least six months. The CO2 produced is passively transferred from the fungi growing environment to an indoor plant growing environment under the optimization of the present invention. The transfer is non-electrical and preferably occurs through a gaseous interchange portal system which provides an interface between the fungi's enclosed plastic bag and the surrounding plant-growing environment.