Last Updated on September 27, 2023



If you’re new to the world of autoclaving (a.k.a. steam sterilization), you may have some burning questions about how lab autoclaves work and what the optimal temperature is for sterilization. In this article, we’ll provide you with the answers you’re looking for, as we delve into the significance of the temperature and other relevant information.

Key Questions About Autoclaves

  • Why is the required temperature typically set at 121 degrees Celsius (121°C)? What makes this temperature ideal for autoclaving lab media?
  • How does the autoclave achieve a temperature of 121°C when water boils at 100°C?
  • Why can’t alternative techniques like bleach, microwaving, or incineration be used for sterilizing lab materials?
  • What happens to the microbes when they are autoclaved?

These are great questions as you look to start up a lab. In this article, we’ll give you the answers. We’ll explain why 121°C is a “magic” temperature for your autoclaving needs, and a lot more.


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Understanding the Importance of Autoclaves

All these questions revolve around the issue of dealing with contaminated materials such as glassware, culture media, and other lab essentials that come into contact with living organisms. These contaminants can include bacteria, fungi, and viruses. When working on projects like developing a new beer variety using yeast, it’s essential to ensure the yeast thrives while keeping bacteria at bay. Sterilization, in this context, is the process of efficiently and effectively neutralizing these microscopic organisms that could contaminate lab materials. Once these microbes are inactivated or killed, they pose no threat, allowing for the safe disposal or reuse of the materials they once occupied.

The Significance of the “Magic” Sterilization Temperature in Labs

For most lab applications, autoclaves are set to the standard sterilization temperature of “121°C for 20 minutes.” But why these specific numbers? How does the autoclave achieve a temperature higher than the boiling point of water? In your kitchen, water boils at 100°C and turns into steam, but inside an autoclave, it’s a different story. The autoclave is a sealed environment, so when water boils and converts to steam, it doesn’t escape into the air. Instead, it remains trapped inside, leading to an increase in pressure as the temperature rises. The Tomy SX-700 Lab Autoclave, for instance, reaches a pressure of 0.25 mega-pascals, while the SX-500 goes up to 0.263 at 121°C.

This pressure buildup allows the temperature to surpass 100°C. While 121 degrees Celsius isn’t necessarily a magical number, it serves as a general guideline for accommodating a wide range of commonly used lab media. However, there may be exceptions based on specific autoclaving requirements for different materials. It’s always a good idea to consult the recommended autoclaving parameters for your particular medium and program the autoclave accordingly.

The Role of Pressure in Autoclave Functionality

The pressure generated when steam exceeds the boiling temperature isn’t just a random outcome of the heating process; it’s crucial for the autoclave’s effectiveness. Picture everything you place inside the autoclave having tiny crevices and cavities, whether it’s the structure of a complex bioreactor or the irregular surface of depleted agar. Achieving thorough sterilization requires extreme heat to reach every nook and cranny.

This is where high-pressure steam comes into play. It forcefully infiltrates all available voids, ensuring that every exposed microorganism is killed. The efficiency and speed of this process are remarkable. For example, Tomy autoclaves feature a dual-fan design, resulting in 42% faster cooling compared to non-fan autoclaves, allowing for increased throughput.

Why Autoclaving Reigns Supreme

Autoclaving is a safer and more effective option for sterilizing lab materials due to its unique advantages. Other methods like incineration, bleaching, or microwaving may not reliably penetrate the tiny voids that high-pressure steam can reach. Incineration can destroy materials entirely, and bleach may not effectively sterilize all areas. Microwaving may lack consistency in achieving thorough sterilization.

If you have any further questions or need assistance, feel free to contact us directly or leave a comment below. We value your input and would be delighted to help you.



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