Last Updated on January 18, 2024


TOMY Lab Autoclave close-upAn autoclave is a versatile piece of equipment used in various industries for sterilization. While autoclaves come in different sizes, shapes, and functionalities, their core method for sterilization remains the same: high-temperature steam and pressure. Whether you are a scientist in a research facility or a professional in a medical or industrial setting, you should understand the inner workings of autoclaves that make them so effective at sterilization. This article will delve deeper into the workings of autoclaves, exploring their components and unique sterilization process.

What is an autoclave?

An autoclave sterilizes instruments, solid or liquid media, and biological waste with highly saturated steam. Superheated steam is far more effective than boiling water, and autoclaves excel at inactivating microorganisms, including those resistant to conventional detergents and sterilizing solutions. Charles Chamberland is credited with inventing the autoclave in 1884. However, heat and pressure had been used for years for sterilization with prototype devices dating back to the late 17th century. Over time, autoclaves have evolved to incorporate numerous features, including safety enhancements, increased effectiveness, automation, and convenience.

The CDC recommends autoclaves as safe and effective methods of steam sterilization. While they’re most often used in labs, their application extends to medical facilities, industrial sites, salons, tattoo parlors, and veterinary practices, among others. Autoclaves can be used to sterilize:

  • Laboratory Equipment: Autoclaves are crucial in laboratory settings for sterilizing glassware such as beakers, test tubes, pipettes, and petri dishes. They can also be used to decontaminate laboratory waste materials.
  • Biological Waste: Autoclaves can safely dispose of biohazardous waste materials like cultures, media plates, contaminated gloves or gowns, and other biological substances.
  • Pharmaceuticals: In pharmaceutical manufacturing processes, autoclaves play a vital role in ensuring sterile production environments by sterilizing containers such as vials or ampoules before filling them with drugs.
  • Food Industry: Autoclaves are used in the food industry to preserve food by eliminating bacteria that could cause spoilage or food-borne illnesses. This can include brewery equipment.
  • And more!

How Does Autoclaving Work?

Autoclaves use three primary components for sterilization: high temperature, pressure, and steam.

1. High Autoclave Temperatures

Autoclaves generate the steam required for effective sterilization by creating high temperatures and pressure. Maintaining precise temperatures is crucial to the autoclave’s ability to create steam and build up pressure. The most common chamber temperature for autoclaves is 121°C (249.8°F), similar to the maximum temperature for a pressure cooker. However, commercially available models can achieve higher temperatures ranging from 130°C (266°F) to 135°C (275°F). For instance, the TOMY Autoclave Sterilizer can reach a maximum temperature of 135°C.

2. High Pressure

Similar to a standard pressure cooker, laboratory autoclaves operate by producing and containing high pressure. Autoclaves harness this pressure to generate steam that effectively sterilizes microorganisms present on laboratory equipment. TOMY Autoclaves, for example, maintain sterilization pressures ranging from 0.019 to 0.212 MPa.

3. Steam Generation and Sterilization

The rise in chamber pressure and temperature leads to the production of steam. When the steam comes into contact with the media, it initiates the autoclave’s steam sterilization process. The transfer of energy from the heat source to the steam destroys microorganisms and breaks down their cell walls and membranes, creating a sterile environment within the chamber.

Sterilization Duration

The time required for autoclave sterilization varies depending on several factors, including the material being sterilized, its porosity, and whether it is packaged or wrapped. A standard guideline for laboratory settings suggests that a temperature of 121°C maintained for 20 minutes is sufficient to eliminate contaminants. However, it is vital to consult specific guidelines for sterilizing that particular media. Larger pieces of lab media or larger volumes may require longer sterilization times.

TOMY Autoclaves offer programmable sterilization capabilities, ranging from 105°C to 135°C, with a maximum sterilization time of 10 hours. These autoclaves can also be programmed for heating, operating between 45°C and 95°C for up to 99 hours. Additionally, a preset timer allows users to delay the start time by up to 99 hours, providing flexibility and convenience in scheduling sterilization cycles.

Gravity Displacement Autoclave

Types of Autoclaves

The two primary types of autoclave sterilizers are gravity displacement autoclaves and pre-vacuum autoclaves.

1. Gravity Displacement Autoclaves:

Gravity autoclaves follow a relatively straightforward sterilization process. Water at the bottom of the chamber is directly heated to produce steam and build up pressure. As the pressurized steam fills the chamber, it displaces the ambient air, eliminating it. The autoclave’s valves are then closed to prevent air from escaping the chamber further. The autoclave continues to increase pressure and temperature until the desired settings are reached, commencing the sterilization cycle.

2. Pre-Vacuum Autoclaves:

Pre-vacuum autoclaves are more intricate in design and less commonly used in laboratory settings. These autoclaves employ a vacuum pump to evacuate the ambient air from the chamber, allowing steam to enter. This process is repeated multiple times until the chamber is entirely devoid of ambient air and filled with steam. The vacuum function enables the steam to penetrate media more effectively, making pre-vacuum autoclaves suitable for sterilizing fabrics, wrapped items, and sterilization pouches.

Choosing the Right Autoclave

Selecting the appropriate autoclave for your laboratory depends on various factors, including the nature of the materials you’re sterilizing and the specific requirements of your environment. If you are new to autoclaves, a gravity displacement type is often the best starting point since it is the most common and suited for a wide range of media. For more robust sterilization needs, you should consider pre-vacuum autoclaves.

In Summary

Autoclaves play a critical role in laboratories and various industries where sterilization is paramount. Using heat, pressure, and steam, autoclaves effectively deactivate microorganisms and create sterile environments. The ability to program specific temperatures and sterilization times makes autoclaves indispensable tools for achieving high-level sterility. When selecting an autoclave, consider factors such as the type of autoclave best suited for your materials and the environmental conditions necessary for your specific purposes.




Find the right autoclave for your needs. Our free guide helps you make an informed decision

Download Free Guide

Tips for How To Sterilize Brewing Equipment With an Autoclave

Previous Article

What Are Autoclaves Used For? Different Ways to Use Steam Sterilizers

Next Article

Recent Blogs & Vlogs

Can You Autoclave It? A Short Guide to What You Can and Can’t Autoclave

Can You Autoclave It? A Short Guide to What You Can and Can’t Autoclave

Autoclaving is an efficient and effective sterilization method for labs, breweries, dentist offices, tattoo parlors, and other places that consistently need sterilized items. However, while autoclaves are effective for many materials, some articles are either unsafe in the autoclave or will degrade when subjected to heat, pressure, and steam. We’ve already explored how autoclaves are […]

How To Spore Test an Autoclave

How To Spore Test an Autoclave

Discover why spore testing is crucial for autoclave sterilization and how TOMY's autoclave selection ensures efficient and safe lab operations.