How Does a Laboratory Autoclave Work?

How Does a Laboratory Autoclave Work

Sterilization is a process that eliminates or kills microorganisms on a surface, object, or fluid. It can be accomplished through various methods, such as heat, chemicals, ionizing radiation, and high pressure.  One method to do this is the use of a laboratory autoclave.

Sterilizing items that come into contact with sterile body tissues or fluids is essential to infection control. It includes items that are used during surgery and reprocessed medical devices.


lab autoclave removes air from the chamber and replaces it with steam. This process is known as the purge phase and occurs before a cycle.

The steam is created in a boiler or an electric generator beneath the chamber. The heat from this steam causes the water to condense and kills microbes.

During the steam sterilization cycle, an automatic whistle blows to release excess pressure from the chamber. The pressure is then returned to ambient levels after the process is complete.

The load's temperature and air and steam discharge taps monitor sterilization. A log book should be maintained for each cycle in the laboratory autoclave.


The temperature used to sterilize a laboratory autoclave depends on the type of materials to be treated. The temperature must be high enough to kill microorganisms but not so hot that they burn the material.

The pressure applied to the materials inside a steam autoclave also influences the temperature of the steam. Higher pressures increase the boiling temperature of the water, increasing the time it takes to reach a specific sterilization temperature.

Liquids can take a very long time to reach the required sterilization temperature, which is why many liquids may need to be placed into smaller bottles and then poured into the pressure vessel of the autoclave. This process requires a long heating-up time, which can lead to the loss of some liquids and bottle bursts.

Ionizing Radiation

Ionizing radiation is a form of electromagnetic energy that removes electrons from atoms and molecules. It is found at the higher end of the electromagnetic spectrum and can travel unseen, passing through air, water, and living tissue.

Manufactured sources, such as radon in rock formations or medical diagnostic imaging equipment, can also produce it. It can cause chemical changes in a person's cells and damage their DNA.

The annual average dose of ionizing radiation in the United States is estimated at 620 mrem (6.2 mSv). It is a combination of natural background radiation and medical exposures.

Ionizing radiation is typically found in gamma rays, X-rays, and the higher energy part of the ultraviolet spectrum. It is used in medical, industrial, and military applications. Ionizing radiation can be deadly, so it should be used with caution.


Filters are one of the most common sterilization techniques used in labs. They differ from steam sterilization or radiation because they do not kill microbes but physically block their passage.

Filtration forces liquid through a membrane with tiny pores that screen out larger particles. Pore sizes can be as small as 0.1 mm (much smaller than bacteria or viruses), allowing most of the liquid's solutes to pass through while trapping any larger particles.

When sterilizing liquid media in a laboratory autoclave, filtration is critical to ensure the load is completely fixed. Both a horizontal and vertical laboratory autoclave can be equipped with a HEPA filter at the pre-vacuum stage to sterilize the air outlet of the chamber before the heating cycle begins.

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