Any four - stroke internal combustion engine needs at least two valves per cylinder: one for intake of air and fuel, and another for exhaust of combustion gases. (en.m.wikipedia.org)
«People in a boat, waiting, terrified, while implacable, unsmiling men, irresistibly strong, seize... maybe the person next to you, maybe you, and with no warning at all, with time only for a quick intake of air you are pitched into freezing, turbulent water and salt and darkness to drown.» (religion-online.org)
Upset stomachs in teething toddlers may be caused by a buildup of saliva and intake of air from crying into their fragile digestive systems. (howtoadult.com)