Green plants carry out both photosynthesis and respiration. During darkness, photosynthesis does not occur but respiration continues. Under these conditions, the plant uses stored carbohydrates. It takes in oxygen and releases carbon dioxide.
Based on this photosynthesis principle ; flora obscuring house ventilation openings will suck and pump oxygen and carbon dioxide respectively from and in house with like hood of causing Hypoxia and Hypercapnia.
Hypoxia is a deficiency of oxygen in tissues. Hypoxia deprives the tissues of an essential requirement for metabolism. The brain, which normally utilizes about 20 % of the total oxygen consumed is very sensitive to hypoxia. The initial signs of hypoxia include dizziness, nausea, disorientation, loss of memory and blurred vision. If prolonged, hypoxia may lead to severe and sometimes permanent changes in the brain.
Hypercapnia refers to the accumulation of carbon dioxide in tissues. This interferes with the acid-base balance in cells, blood and tissue fluids. This in turn interferes with the activity of enzymes which are very sensitive to changes in pH. Hypercapnia leads to a depression of the central nervous system resulting in confusion and decreased sensation. If prolonged, coma and death may result. In view of this, beautification flora should be trimmed periodically to convenient height.