There is provided a method of determining whether a first type of liquid is being used in a nebulizer, the method comprising obtaining a measurement of the time taken by the nebulizer to nebulize a specified volume of liquid that was held therein, comparing the time taken to nebulize the specified volume of liquid to an estimated value for the time required to nebulize the same volume of the first type of liquid, and determining whether the liquid nebulized by the nebulizer was the first type of liquid based on the comparison.
