How an Autoclave Works & How We Save You Time & Money

All autoclaves use principles similar to that of pressure cookers: the door locks and forms a sealed chamber, where all the trapped air is replaced with steam. The steam is then pressurized for a certain period of time so that the objects within are sterilized. Afterwards, the steam is released so that the objects can be removed. The general phases of sterilization are as follows:

• Conditioning: the chamber is sealed and steam begins to displace the air present, as the temperature and pressure start to increase at a steady rate.
• Exposure: the autoclaves’ control system closes the exhaust valve, allowing for the temperature and pressure to increase to and be maintained at the desired point.
• Exhaust/Drying: the pressure and steam are released from the autoclave’s chamber through an exhaust valve which causes the interior to return to room temperature.

The two most common sterilization cycles used include:

• Gravity: The gravity-displacement process is the most basic of the two. Steam displaces air in the chamber by gravity through a drain port. No mechanical assistance is required. Because the removal of air is more passive, gravity cycles often take longer than other processes.
• Pre-vacuum: Using this method, air is removed using a vacuum pump and pressure pulses. The steam can penetrate porous areas of the autoclave load, unlike more simple methods such as gravity-displacement.

Besides gravity-displacement and pre-vacuum sterilization cycles, which utilize their own methods of air removal, there are several other types of air removal methods used in autoclaves, and the main ones are as follows:

Vacuum Pumps

The vacuum pump, seen in pre-vacuum and/or post-vacuum sterilization cycles, is a method of air removal that relies on sucking air or steam and air mixtures from the chamber. This is useful in situations where extraneous air pockets (e.g. porous areas) could be trapped in the load.

Steam Pulsing

This method relies on using steam pulses to dilute the air. This is done by pressurizing and then depressurizing the change to near atmospheric pressure.

Superatmospheric Cycles

This method relies on a vacuum pump that uses steam pulsing afterward. The number of pulses necessary will depend on the make, model, and chamber size.

Subatmospheric Cycles

Similar to superatmospheric cycles, this method involves a vacuum pump followed by steam pulsing. The chamber never exceeds atmospheric pressure until the autoclave temperature is achieved.

Downward Displacement/Gravity

This method is the simplest way to remove air. Steam enters the chamber, filling the upper areas first because of relative density compared to the air. Air is gradually pushed to the bottom of the chamber and out through a drain, which also generally functions as an autoclave temperature sensor. This is done until the chamber reaches the required sterilization temperature.

The proper packaging and containment of infectious materials are crucial. The most frequent reason for sterilization failure is the lack of contact between the steam and microorganisms.

Dry material (e.g. dry supplies, equipment, instruments, etc.) should be separated from liquid material to achieve proper sterilization. This is achieved using autoclavable bags, which are loaded with the material to be sterilized. The bag should be no more than 75% full, and should typically be left open in order to ensure steam can reach inside. If the autoclavable bag is steam resistant, it must be left open or have holes punched into the top to allow the steam to penetrate.

Furthermore, it’s important to note bags that allow steam penetration tend to melt or crumble during the sterilization cycle. These bags can also leak, so they should be placed into a shallow stainless steel pan.

In addition, each load should include heat sensitive autoclave tape with chemical indicators that will show whether or not the device has reached normal operating temperatures and pressure.

The amount of objects you can load into the autoclave will depend on the unit you buy. It’s important to check with the manufacturer the exact weight the device can hold per cycle.

A prototype of the autoclave, a high-pressure cooker referred to as a “steam digester”, was developed in 1679 by the French physicist Denis Papin. However, it wasn’t until 200 years later that a new version would be created by the French microbiologist Charles Chamberland, which would go on to be used in medical applications.

As the science and importance of sterilization became more widely understood throughout the late 1800s and early 1900s, modern autoclave technology was developed in parallel. By the 1930s, the first pressure steam sterilizer was created, and was designed to control performance by measuring the temperature in the chamber drain line. Subsequent developments followed throughout the 20th century.

While autoclaves have numerous sterilization, cycle, and air removal options, the system functions remain remarkably similar. Understanding the critical role autoclaves play in the medical and research industries is important for those looking to lease:

• Research: It is important to note that many autoclaves used for medical functions are not particularly useful in research applications. This is because the more standard research-grade autoclaves place a premium on ease-of-use, efficiency, and flexibility, while medical autoclaves need a more direct focus on sterilization.
• Medicine: The main focus of medical-grade autoclaves is to neutralize or remove all viruses, bacteria, fungi, and spores on equipment and instruments. This is due to the consistent need to use these items directly on humans, hence the emphasis on preventing contamination and infection.
• Dental: A dental autoclave or a dental sterilizer, is a device that uses steam sterilization or dry heat sterilization to sanitize dental tools. Working in a human mouth can expose equipment to millions of germs that, if not properly cleaned, can lead to dangerous bacteria being passed on to patients.