Last Updated on September 3, 2021
Walk into any laboratory around the world and you are almost certain to find an autoclave sterilizing lab media. Whether the lab is a small pharmaceutical startup, or a large university research facility, sterilizing laboratory media is crucial in carrying out complex scientific research.
Choosing the right autoclave for your laboratory can increase efficiency and lower lab operating costs – but today we look inside the autoclave sterilizer to see just how the sterilization process works. How autoclave sterilization works is a straightforward process; autoclaves operate under a set of scientific principles to carry out a job that is nothing less than critical.
3 Components Needed for an Autoclave to Sterilize
An autoclave is a common piece of laboratory equipment that works to sterilize lab media using three primary components: temperature (heat), pressure, and steam.
1) High Autoclave Temperatures
Precise autoclave temperatures are key in how an autoclave works to create steam and build pressure. The most typical chamber temperature for an autoclave is 121°C. Most commercially available autoclaves will achieve higher temperatures in the 130°-135°C range, including the TOMY Autoclave Sterilizer, which has a maximum temperature of 135°C. Autoclaves work by creating high autoclave temperatures and pressure that create steam to sterilize.
2) High Pressure Builds Up
Similar to a standard pressure cooker, laboratory autoclaves work by producing high pressure. In a food pressure cooker, the high pressure works to quickly cook food. In a laboratory autoclave, the pressure is used to generate enough steam to sterilize the microorganisms present on lab equipment. Inside a TOMY Autoclave, sterilization pressures range from 0.019 to 0.212 MPa.
3) Creates Steam that Sterilizes
The steam generated from the rise in chamber pressure and temperature comes in contact with the media inside, which is where the real autoclave sterilization process begins. The energy transferred from the heat destroys the microorganisms and breaks down cell walls/membranes – creating a sterile environment inside the chamber.
How long does an autoclave take to sterilize?
The easy answer here is it depends. The CDC states “The two common steam-sterilizing temperatures are 121°C (250°F) and 132°C (270°F)”, so it is easy to see the time necessary to sterilize a piece of media differs from object to object.
Sterilization time depends on the material, its porosity, and whether it is in some type of sterile packaging or wrap. In most laboratory settings, 121°C for 20 minutes will kill contaminants, but please check the specifics for your media type. To sterilize larger pieces of lab media or large volumes of lab media, it will take longer.
TOMY Autoclaves are programmable to sterilize (at 105–135°C temperatures) for up to 10 hours. They are also programmable to heat (at 45–95°C temperatures) for up to 99 hours. A preset timer allows you to delay the start time by up to 99 hours, by setting your autoclave to sterilize at the most convenient time.
How Different Types of Autoclaves Work
There are two primary types of autoclave sterilizers – gravity displacement autoclaves and pre-vacuum autoclaves also called pre-vac for short. These two types of autoclaves move steam in different ways to sterilize the media inside the chamber, including glass, liquid media, and laboratory waste.
How Gravity Autoclaves Work
Gravity autoclaves are fairly basic in their sterilization process. Water at the bottom of the chamber is directly heated to create steam and pressure. This pressurized steam then forces the ambient air, previously in the chamber, out. Once the chamber volume is filled with steam, the autoclave is programmed to close the necessary valves, not allowing any more air to escape the chamber. The autoclave works by continuing to build the pressure and temperature until it reaches the desired settings. At this point, the cycle begins and the sterilization process is underway.
Note: TOMY SX model autoclaves are gravity displacement autoclaves with the chamber oriented vertically to maximize throughput. The image above pictures a horizontal chamber.
How Vacuum Autoclaves Work
Vacuum autoclaves are more complex in their design than gravity autoclaves and are not as commonly used in laboratories. Vacuum autoclaves work by using a vacuum pump that forces the ambient air out of the chamber, allowing steam to enter. This process is repeated several times until the chamber has been completely evacuated of ambient air and filled with steam. Because of the vacuum function “pulling” the ambient air out of the chamber, the steam is allowed to penetrate the media. For this reason, vacuum autoclaves are more suited for fabrics, wrapped items, and sterilization pouches.
Whether used in research, pharmaceutical, or a medical laboratory, it is important to choose the right type of autoclave for your purposes. Check out this video showing more information about the 2 primary types of autoclaves and how to choose the right autoclave for your lab.
For more information on how autoclaves work, contact our technical experts or leave us a message in the comments below.