The duration of a nitrous oxide cylinder depends on several factors, including:

• Cylinder size:Larger cylinders, such as 20-pound cylinders, will naturally last longer than smaller ones.
• Rate of consumption:The rate at which the nitrous oxide is administered will significantly impact how long the cylinder lasts. Higher flow rates will deplete the cylinder more quickly.
• Mixture ratio:The ratio of nitrous oxide to oxygen in the mixture can also affect consumption. A higher concentration of nitrous oxide will be used at a faster rate.

It's difficult to provide an exact duration without knowing these specific factors. However, a typical 20-pound cylinder can last for several hours of continuous use under moderate conditions.

It's important to note that nitrous oxide cylinders should be periodically checked to ensure they are not empty. Running out of nitrous oxide during a procedure can be disruptive and stressful for both the patient and the dentist.