Medical oxygen tanks can be made from either aluminum or steel. In the United States, all medical tanks and cylinders are color-coded. Oxygen always comes in a green tank. If you are working in another country, be sure to check that the coding system is the same. While steel is much heavier than aluminum, both materials are in use as of 2011.
The tanks must be filled with medical-grade oxygen, which is 99 percent pure. You must use a regulator to control the pressure of the oxygen exiting from the tank and to control the flow to the patient. Next, the oxygen device is connected. This may involve a mask, a nasal cannula or some specialized design. These devices are usually put on with a quick connector.
As a nurse or technician, your most important consideration is how long a tank will last. Of course, there are large tanks and small tanks, and the flow rate can be different for each patient. To determine how long the tank will last, you need to know the size of the tank, how full (how much pressure in pounds per square inch) the tank is and what the flow rate to the patient is.
To calculate the time an oxygen tank will last, you take the factor associated with the tank size (for example 0.28 for an E tank), then multiply it by the pressure in pounds per square inch (psi) in the tank and divide this answer by the flow rate. As an example, you have an E tank partially full with 1,500 psi and a flow rate of 3 liters per minute. The tank's oxygen will last 148 minutes, or two hours and 28 minutes.
The most common tanks are a small, transportable D tank, the larger E Tank, and the M, G and H/K tanks, which are installed in the hospital. The factors are as follows: D is 0.14, E is 0.28, M is 1.4, G is 2.2, and H/K is 2.8. Try out the following example and see if you get 105 minutes. You have a D tank with 1,500 psi and a flow rate of 2 liters per min.