Frequently asked questions

Models that need to be installed (i.e. this excludes compact and benchtop units) should be connected to a vented drain, which will eliminate the possibility of back-flow.

Simple vacuum will improve air removal from discard loads (in comparison with freesteaming), although the most efficient form of air removal is Advanced (pulsed) vacuum.

Yes, although care should be taken to ensure that the autoclave is not overfilled, since this may prevent efficient air removal.

BSL3 is generally hazardous waste containing pathogens that are potentially harmful. Further details can be provided on request.

The Classic and Autofill Compact and Benchtop autoclaves can be used for small quantities of non-hazardous discard. For larger, difficult loads a vacuum system is beneficial. If BSL3 (Cat3)   waste is being sterilized, a heated jacket in addition to vacuum, would be recommended, since this ensures improved temperature distribution within the chamber. 12 point validation to a recognised standard is recommended to ensure that all parts of the load are being sterilized.

Operator specific cycles can be provided on request. Please contact Astell for further details.

Up to 5,000 cycles can be stored, although this may vary depending on cycle parameters.

The Astell controller allows the programming of at least 50 different cycles.

Freesteaming involves 'air purging', where air is effectively 'driven' from the chamber & load using turbulent steam. Pre-vacuum withdraws air from the chamber using a vacuum pump.

Yes, a media melting/warming cycle is available.

No, the holdwarm system is dependent on the remaining water in the chamber being held at a constant temperature. If an autoclave has a steam generator little or no water remains in the end of the cycle.

If the water supply is relatively hard (<50ppm) a Water Softener would be advisable. This is particularly critical for units with a steam generator, where any build up of scale will not be visible, and the first sign of unsuitable water may be heater failure.

An autoclave without an Autofill system will need to be manually filled before each cycle. However, please note that in normal circumstances some water will remain in the chamber at the end of each cycle, so the water required to reach the minimum level will be relatively small. Note: The latter applies only to autoclaves with heaters in the chamber; an autoclave fitted with a steam generator will fill automatically (and therefore will require a water supply).

Air Ballast reduces the risk of bottled fluids boiling over when an efficient cooling system (e.g. water jacket cooling) causes a sudden change in pressure within the autoclave chamber. Therefore when an autoclave is fitted with air ballast the cooling stage can be implemented earlier; this will mean that improved cooling times can be achieved.

A dry discard cycle is intended for the sterilization of waste loads that contain little or no liquid. Often these will consist of petri dishes, and other plastic containers etc. that require decontamination prior to disposal

Pipettes and textiles can be sterilized in any autoclave. However, in most cases these products will need to be dry at the end of the cycle, and for this an Advanced Vacuum and Heated Jacket will be necessary.

Cycle times are very much dependent on the size and nature of the load being sterilized. However, for identical loads, an Autofill unit will have a slightly (up to 15%) faster cycle time than a Classic unit. This is because with the Autofill version the hot water is ejected from the chamber after sterilization, whilst with the Classic unit, the water remains.

Autoclaving Glass Bottles and Plasticware in the Laboratory: A Comprehensive Guide

Autoclaving is a widely used technique in laboratories for sterilizing equipment and materials, including glass bottles and plasticware. Sterilization is crucial for preventing contamination of experiments and ensuring reliable results. Here is a comprehensive guide on how to safely autoclave glass bottles and plasticware in the laboratory.

Step 1: Select the Appropriate Autoclaving Equipment

There are different types of autoclaves, including vertical and horizontal ones. The choice of autoclaving equipment depends on the size and quantity of materials to be sterilized. Vertical autoclaves are suitable for sterilizing small volumes of materials, while horizontal autoclaves are ideal for large volumes. It is important to choose an autoclave that can accommodate the materials to be sterilized.

Step 2: Choose the Right Glass Bottles and Plasticware

Not all glass bottles and plasticware are autoclavable. It is important to select glass bottles and plasticware that are heat-resistant and can withstand high pressure and temperatures. Glass bottles made of borosilicate or tempered glass are suitable for autoclaving. Plasticware made of polypropylene or polyethylene can also be autoclaved. Avoid autoclaving plasticware made of polycarbonate, as it can become deformed or damaged by high temperatures.

Step 3: Prepare the Glass Bottles and Plasticware

Before autoclaving, ensure that the glass bottles and plasticware are clean and free from any contaminants. Rinse them thoroughly with deionized water to remove any residues or impurities. Dry the glass bottles and plasticware in a sterile environment, such as a laminar flow hood or a clean bench.

Step 4: Load the Autoclave

Arrange the glass bottles and plasticware in the autoclave according to the manufacturer's instructions. Avoid overcrowding the autoclave, as this can lead to inadequate sterilization. Leave enough space between the materials to allow steam to circulate freely. Also, ensure that the glass bottles and plasticware are securely fastened to prevent breakage during autoclaving.

Step 5: Autoclave the Materials

Set the autoclave to the appropriate temperature and pressure, depending on the materials being sterilized. The recommended temperature for autoclaving glass bottles and plasticware is 121°C for 15 to 30 minutes at a pressure of 15 psi. Once the autoclaving process is complete, allow the materials to cool down before removing them from the autoclave.

Step 6: Store the Sterilized Materials

Store the sterilized glass bottles and plasticware in a clean and dry environment to prevent contamination. Label them appropriately to ensure that they are used for their intended purpose. It is important to note that autoclaved glass bottles and plasticware can become brittle over time, especially with repeated autoclaving. Therefore, it is advisable to replace them periodically.


Autoclaving glass bottles and plasticware is an effective method of sterilization in the laboratory. However, it is important to select the appropriate materials, prepare them properly, and follow the correct autoclaving procedures to ensure reliable and consistent results. By following the six steps outlined in this guide, you can safely autoclave your glass bottles and plasticware, and minimize the risk of contamination in your experiments.

How to Sterilize Discard and Waste

  1. Choose the right autoclave and loading method based on the type of waste and discard materials you need to sterilize. There are different types of autoclaves, but the two most common are gravity displacement and vacuum-assisted. Gravity displacement autoclaves are simpler and rely on steam and gravity to sterilize, while vacuum-assisted autoclaves use a vacuum pump to remove air from the chamber before steam is introduced. Loading autoclaves correctly is also crucial to ensure effective sterilization.
  2. Load autoclaves loosely and in a way that allows for effective steam penetration. For example, bags of waste should not be sealed and the top must be opened up completely and ideally rolled down so that the maximum area of the load is exposed to the steam without the top of the bag getting in the way. A small amount of water can also be added to the bag upon loading to aid steam penetration.
  3. Run the autoclave according to the instructions the product instructional manual. If you require further assistance, contact the Astell Service Department. Depending on the type of autoclave and the load size, the sterilization cycle may take anywhere from a few minutes to several hours.
  4. Proper waste management is essential to ensure that sterilized waste and discard materials do not pose a threat to public health or the environment. Autoclaved waste can be disposed of in general waste bins if it is not hazardous or biohazardous. However, if the waste is considered hazardous or biohazardous, it must be disposed of in accordance with your areas jurisdictional regulations. This may require special disposal procedures, such as incineration or chemical treatment.