By harnessing the power of steam, pressure, and time, autoclaves can effectively eliminate microorganisms and spores, ensuring a safe and sterile environment.

PRIMUS Sterilizer


In medical and laboratory settings, the need for effective sterilization and disinfection of equipment and waste is paramount. One of the most widely used methods for achieving this is using autoclaves (or sterilizer).

Autoclaves utilize a combination of steam, pressure, and time to eliminate microorganisms and spores that may be present. In this comprehensive guide, we will delve into the intricacies of autoclaves, exploring their working principles, suitable materials, dos and don’ts, and the importance of autoclave validation.

How Do Autoclaves Work?

Autoclaves are designed to harness the power of steam sterilization. The process primarily relies on three key factors: temperature, pressure, and time.

Effective sterilization occurs when the steam temperature exceeds 250°F (121°C) and the autoclave is pressurized to at least 20 psi. The duration of the sterilization process depends on the temperature and pressure settings, with a minimum of 30 minutes required at 250°F (121°C) and 20 psi.

By subjecting the materials to these conditions, autoclaves eliminate microorganisms and spores.

Laboratory sterilizers

Vivarium sterilizers

Healthcare sterilizers

The Dos and Don’ts of Autoclave Use

To ensure safe and efficient use of autoclaves, it is essential to adhere to a set of guidelines.

Let’s explore the dos and don’ts of autoclave use:


  • Use ORANGE autoclavable biohazard bags: When autoclaving waste, it is crucial to use designated autoclavable biohazard bags, preferably in the color orange. These bags are specifically designed for the safe disposal of biohazardous waste.
  • Add water to the bag before closing: Before closing the biohazard bag, adding approximately 250 mL of water is recommended. This step helps create a humid environment within the bag, enhancing the effectiveness of the sterilization process.
  • Autoclave bags in a designated container: Place the autoclave bag in a stainless steel or autoclave-safe polypropylene secondary container. This secondary container provides an added layer of protection during the sterilization process.
  • Proper disposal: Once the autoclaved bag has cooled, it should be placed in a regulated medical waste box for proper disposal. Following the designated waste disposal protocols is crucial to prevent potential risks.
  • Maintain cleanliness: Clean up after using the autoclave to ensure a safe and hygienic environment for all laboratory personnel. This includes cleaning spills, wiping surfaces, and ensuring the autoclave room is tidy.
  • Prompt removal of waste: Remove waste from the autoclave promptly to allow others to utilize the equipment efficiently. Leaving full autoclave bags on the floor or allowing them to accumulate in the lab or autoclave room can create hazards and disrupt workflow.


  • Use RED biohazard bags: Avoid using red biohazard bags for autoclave waste. Red bags are typically reserved for other types of waste and may not be suitable for effective autoclaving.
  • Leave bags in the autoclave after the run is done: After completing the sterilization cycle, it is essential to promptly remove the autoclave bags. Leaving them in the autoclave for an extended period can lead to moisture buildup and potential contamination.
  • Leave full autoclave bags on the floor: Full autoclave bags should never be left on the floor. Proper disposal and containment are essential for maintaining a safe and organized laboratory environment.
  • Expect janitorial staff to handle autoclave bags: The janitorial staff is not trained to handle biowaste. Therefore, it is essential to dispose of autoclaved bags in designated waste bins rather than leaving them outside for general janitorial staff to handle.
  • Let autoclave bags accumulate: Avoid allowing autoclave bags to accumulate in the lab, autoclave, or autoclave room. Regular disposal and maintenance are necessary to ensure a clean and efficient workspace.
  • Use autoclave bags for non-biohazardous waste: Autoclave bags should only be used to collect biohazardous waste. Utilizing them for other purposes may lead to contamination and compromise the sterilization process.

Compatible and Incompatible Materials

Autoclaves are suitable for sterilizing a wide range of materials, but it is crucial to understand which items are compatible and which are not.

Let’s explore the materials that can and cannot be treated using an autoclave

Compatible Materials

  • Tissue Culture Flasks: Autoclaves are commonly used to sterilize tissue culture flasks, ensuring a sterile environment for cell culture experiments.
  • Surgical Instruments: Autoclaving surgical instruments is critical in ensuring their sterility before use in medical procedures.
  • Glassware: Glassware used in laboratories, such as beakers, test tubes, and petri dishes, can be safely sterilized in autoclaves.
  • Pipette Tips: Autoclaving pipette tips is essential to maintain a sterile environment and prevent contamination during experiments.
  • Media Solutions: Autoclaves are commonly used to sterilize media solutions, ensuring a sterile growth environment for microorganisms or cell cultures.
  • Animal Food and Bedding: Autoclaving animal food and bedding is crucial for maintaining a clean and sterile environment in animal research facilities.
  • Waste: Autoclaves are utilized to decontaminate biological waste, ensure safe disposal, and prevent the spread of pathogens.
  • Polypropylene (Secondary Containers): Autoclave-safe polypropylene containers are compatible with autoclaves and provide an additional layer of protection during sterilization.
  • Stainless Steel: Stainless steel materials, such as surgical instruments or containers, are compatible with autoclaves and can withstand high temperatures and pressures.
  • Gloves: Autoclaving gloves are essential for maintaining a sterile environment and preventing cross-contamination in laboratory settings.

Incompatible Materials

  • Acids, Bases, and Organic Solvents: Autoclaves should not be used to sterilize materials that contain acids, bases, or organic solvents. These substances can react with steam and potentially cause hazardous situations.
  • Chlorides, Sulphates: Materials containing chlorides or sulfates should not be autoclaved, as they can react with steam and create corrosive byproducts.
  • Seawater: Seawater should not be subjected to autoclaving due to its high salt content, which can cause corrosion and damage to the autoclave.
  • Chlorine, Hypochlorite, Bleach: Autoclaving materials containing chlorine-based compounds, such as bleach, can generate toxic gases and damage the autoclave.
  • Non-Stainless Steel: Non-stainless steel materials may corrode or react with steam during autoclaving, making them incompatible with sterilization.
  • Polystyrene (PS): Polystyrene materials, commonly used in disposable plasticware, should not be autoclaved, as they can melt or deform under high temperatures and pressures.
  • Polyethylene (PE): Polyethylene materials, including low-density (LDPE) and high-density polyethylene (HDPE), are not suitable for autoclaving due to their low melting points.
  • Polyurethane: Autoclaving polyurethane materials can cause them to degrade, resulting in changes to their physical properties and potential failure.

Never Autoclave

Flammable, Reactive, Corrosive, Toxic, or Radioactive Materials: Autoclaves should never be used to sterilize materials that fall into these categories, as they can pose serious risks and potentially damage the autoclave.

Household Bleach: Household bleach should never be autoclaved, as it can release toxic gases and damage the autoclave.

Liquid in Sealed Containers: Liquids sealed in containers should not be autoclaved, as the pressure generated during the process can cause the containers to rupture.

Material Touching the Interior Surfaces of the Autoclave: Materials that come into direct contact with the interior surfaces of the autoclave should not be autoclaved, as it can lead to contamination and potential damage to the autoclave.

Paraffin-Embedded Tissue: Autoclaving paraffin-embedded tissue should be avoided, as the melted paraffin can cause significant damage to the autoclave.

Autoclave Validation

Regular validation is necessary to ensure the effectiveness of autoclaves in decontaminating biowaste. Autoclaves used in this capacity are typically validated quarterly by Environmental Health and Safety (EHS) departments.

The validation process involves using biological indicators, such as Geobacillus stearothermophilus spores, to test the autoclave’s efficacy in inactivating bacterial spores. If the test fails, service is requested to address issues to ensure the sterilizer is appropriately functioning.


Sterilizers are powerful tools in the fight against microbial contamination and the sterilization of laboratory equipment and waste. By harnessing the power of steam, pressure, and time, autoclaves can effectively eliminate microorganisms and spores, ensuring a safe and sterile environment.

Adhering to proper procedures, understanding compatible and incompatible materials, and ensuring regular autoclave validation are essential for the successful and safe use of autoclaves.
With the knowledge gained from this guide, you now know how to maintain a clean and sterile laboratory or healthcare environment effectively.

Have technical questions about PRIMUS sterilizers?  Talk to Dave Schall at 877.679.7800 extension 1212 or email at

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During the intensive 3-day course, Spire Integrated Solutions customers and ASA Service professionals deep dive into a PRIMUS sterilizer’s inner workings and possible repairs.

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