The aerenchyma or aerophilic parenchyma or lagoons, is a modification of the parenchyma to form a spongy tissue that creates spaces or air channels in the leaves, stems and roots of some plants, allowing gas exchange between the shoot and the root. In plants, the substomatal cavity is the cavity located immediately proximal to the stoma. It acts as a diffusion chamber connected to intercellular air spaces and allows the rapid diffusion of carbon dioxide and other gases (such as plant pheromones) into and out of plant cells. Spongy plant tissue composed largely of air spaces that allow the exchange of gases by diffusion in the underground roots of mangroves.
Older homes generally have pipe fittings called air chambers located on each hot and cold water line at or near each faucet or water inlet valve and are rarely visible. The air chambers act as a shock absorber for water flowing at high speed.
Inhalation or exposure to negative ions is quite safe for humans, since negative ions are already naturally present in our environment from sources such as sunlight, lighting, and waterfalls. However, it is the ozone production of these ionic air purifiers that poses a risk to human health.