Typically, head hood reliably deliver oxygen concentrations of 60 percent or less. However, with adequate sealing (foam or blankets occluding the openings) and adequate liter flow (typically 5-7 liters/minute), as well as utilization of a source of 100 percent oxygen, it is possible to achieve inspired oxygen content 80 percent or more. This level of gas delivery is typically adequate to wash out the expired carbon dioxide through leaks in the hood so that this gas does not build up. The incoming gas is typically warmed and humidified, although this can lead to fogging, which limits visibility and may provide an infection risk. Head hoods may be placed on infants in cribs, radiant warmers, or incubators. Hoods may also be used in conjunction with a nasal cannula to increase the inspired oxygen content.