While having one type of oxygen tank seems efficient, there are many different options on the market. This is designed to give people just the right oxygen delivery for their needs.
These tanks are what people typically think of with oxygen. These tanks are inexpensive and usually covered by insurance. Though they are heavy, you can fill a small portable tank from them. Even small units can be heavy and you will need to take care to keep them upright to avoid issues with the tank.
When oxygen is in a cold state, it turns to liquid. This liquid allows for a greater amount of oxygen to be placed in a tank and weigh less than a compressed oxygen tank. As with the compressed oxygen, it can be filled into smaller units for portability purposes. There are some disadvantages of these units of which to be aware. For one, it is more expensive than compressed oxygen and does not have as long of a shelf life as it will evaporate. Also, you will not be able to take liquid oxygen tanks on a plane.
Oxygen Tank Sizes
Another thing to keep in mind is the size of the unit. There are two different ways this is measured. The old way was to give them letters ranging from A to E, where A was the smallest unit and E the largest. The new way is to label them with M (for medical) with a number. The number signifies the cubic feet of oxygen that the unit will hold. Most suppliers will show you the conversion of the old technique to the new to ensure you get the size that is right for you.