An Air detector is fitted to certain sterilizers which employ vacuum as a means of removing air from the load before sterilization. It is used to determine whether any air or non-condensable gas present in the chamber is sufficient to impair the sterilization process.

A metering device (such as a needle valve) is required to admit air into the sterilizer chamber for the air detector tests, vacuum and pressure leak tests. The device should be capable of controlling the flow of air into an evacuated chamber.

It should be adjustable and have a range which includes a flow of 0 to 5 ml min^-1 per litre volume of the sterilizer chamber. The error in repeatability between 10% and 90% of the setting range should not exceed ± 5%. The device is connected to the chamber by a valved port provided by the sterilizer manufacturer.