What is an air detector in an autoclave?

Oct 1 / Chris Maughan

Autoclaves are essential for sterilizing products and materials in industries such as hospitals, biotechnology, pharmaceuticals, and medical devices. Sterilization loads are typically divided into two categories: fluid loads and dry goods (porous) loads.

Air or non condensable gases (NCGs) can prevent steam from fully penetrating the load, which could inhibit sterilization. 

Air detectors are used as a routine method of detecting air or NCGs within the chamber during production cycles. 

Sources of air in a Porous Load / Hard Goods Autoclave

At the start of the cycle the chamber is 100% air and the cycle is designed to remove as much as possible. This is done by using a vacuum pump and pulsing steam into the chamber. Additional air can come into the chamber via leaks, as non condensable gases in the steam supply or be generated from load items.

What is an air detector and how does it work?

An air detector is used to detect the presence of air in a porous load cycle. This is crucial because air pockets can prevent sterilization. There are two main types of air detectors:

  • Temperature-Based Air Detector: This method creates a "worst-case" scenario location where air is likely to collect. The temperature is then measured in this area; if air is present, it will show a colder temperature compared to the surrounding steam.

  • Pressure-Based Air Detector: This method works by collapsing a steam sample and measuring the pressure. The more non-condensable gases (such as air) present in the steam, the higher the pressure will be.


The air detector compares the results against pre-defined setpoints. If the setpoints are met, the cycle continues as normal. If not, the cycle will be aborted, and a cycle failure will occur.

Where can learn more about air detectors?

For detailed information on air detectors and their setup, refer to ISO EN-285. Or watch our Free webinar 'Introduction Air Detectors'.

You can also learn more about air detectors and their configuration in our Advanced Autoclave Validation training course. 

How can we help?

We can offer consultancy support, training or validation engineers to help setup your air detector.
Write your awesome label here.