1-liter and 2-liter oxygen generators belong to the health-care type, and when the gas flow rate is adjusted at 1L/MIN, the oxygen concentration can reach 9%. But for the patient, the airflow is small.
3-liter and 5-liter oxygen generators belong to medical type. Patients must use 3 liters or 5 liters.
the oxygen concentration can reach more than 95% when the gas flow rate of 3 liters is adjusted to 3 liters/min.
for patients, the air flow is enough. A 5-liter machine is usually used by two people at the same time or with a ventilator.