The capacity of an oxygen cylinder depends on the specific needs of the user. Here are some common oxygen cylinder capacities and their applications:

2 liters (small capacity): These small capacity oxygen cylinders are commonly used for portable use such as outdoor activities, first aid, or brief home care.
5 liters (medium capacity): These medium capacity oxygen cylinders are commonly used for home care for patients who require regular oxygen but have good mobility.

10 liters or more (high capacity): High-capacity oxygen cylinders are for patients who require continuous oxygen, such as those with chronic obstructive pulmonary disease (COPD) or other serious breathing problems. They can also be used in medical facilities.