An H cylinder has the capacity to hold roughly 7,000 liters of oxygen. H cylinders are the largest semi-portable tanks in common use. When fully charged, an H cylinder provides high-flow oxygen to a patient for well over six hours.
H cylinders are employed in medical environments where patients require continuous care. Larger and heavier than their more portable counterparts, H cylinders need to be mounted to a wheeled hospital bed, an ambulance or another piece of heavy equipment in order to be effectively moved or transported. These cylinders are common sights in many hospitals, medical facilities and EMS systems that provide pre-hospital care.