Autoclave sterilizers are essential for almost any type of laboratory. It is crucial to choose the autoclave that suits your needs. Autoclaves come in many shapes and sizes, it can be overwhelming to make the right selection. And stressful wondering whether you have made the correct decision. Choosing the right autoclave depends on several factors.
To assist you in your autoclave search, we have outlined the most significant factors that will help you choose the right autoclave for your sterilizing needs.

Type of Sterilization Media

Autoclaves function through either gravity or vacuum-induced or pre-vacuum (prevac) sterilization methods, though some types of autoclaves combine both methods to sterilize.

For the most commonly used types of sterilization media, including glassware, utensils and non-porous items, gravity displacement steam autoclaves are used. Whereas for large and non-porous items such as blankets and other media, vacuum type sterilizers are recommended.

Autoclave Size

One of the most important things to check is that the autoclave is large enough to fit the largest items that you will be autoclaving.
Autoclave size is often measured in Liters. A unit that measures the total volume of the inside of the chamber, yet, the effective chamber size is usually smaller than the actual chamber size.

Not only is the capacity of the chamber important, but one must consider the configuration of the autoclave chamber to determine whether the autoclave will meet your size needs.

Most laboratories and start-ups do not need a huge autoclave. Especially one that requires a large amount of space, plumbing, electricity and house steam. Not to mention significant monetary and time investments for installation, maintenance, and opportunity costs when an autoclave requiring a large amount of technical expertise breaks down.

Throughput Capacity

Second, the throughput capacity will determine whether your autoclave is suitable for the amount of autoclaving media that must be sterilized on a daily basis. To determine an autoclave’s throughput, the amount of autoclaving media that can be sterilized per cycle (as well as the amount of time needed to prepare, load, and unload media) would determine whether a given autoclave would meet your daily sterilization needs.

Autoclaves have different warm-up and cool down times that can add to the cycle time. Certain features, such as cooling fans can speed up this process, in some cases allowing for more cycles in a day and a higher throughput.

Autoclave and Benchtop Space

You should assess the space that you have available in deciding what type of autoclave to buy. Autoclaves come in many shapes and sizes, which have advantages and disadvantages.

The following reasons lead to significant waste for front-loading autoclaves:

  1. Inside the box/outside the chamber. To start, autoclave chambers are cylindrical due to physics, which need equal pressure throughout the chamber. Horizontal autoclaves are sideways facing cylinders enclosed by a box. With this design, the spaces around the outside of the chamber within the box gets wasted.
  2. Within the chamber. Items must have a flat surface on which to rest, accommodated by using trays that slide into the chamber. With this system, the areas outside of the flat surface inside the cylindrical chambers are wasted.
  3. On the tray. Autoclave media, especially glassware tends to be round in shape, including flasks, bottles, petri dishes, etc. When placing round objects on a rectangular area, the areas along the edges are also lost, as round objects only come in contact with the edge of a tray at one small point. The rest is lost space.

Basic lesson- circles and squares do not mix. This principle works the same with autoclaves.

So, top-loading autoclaves are much more efficient in their use of space. The vertical configuration of top-loading autoclaves and stackable baskets allow for the most efficient use of the vertical cylindrical chamber. Combined with the round-shaped sides, top-loading autoclaves can accommodate large capacities of autoclave media, which tend to have round edges.

Installation Utilities: Water and Electricity

Access to water is an important factor, as some autoclaves need plumbing. Others can function by adding water to the unit. But, not all water is equal when it comes to steam sterilization. Much of the tap water in the Unites States contains a high mineral content, including lime, which can calcify and leave residue on the autoclave’s heater and within the chamber. This will cause irreversible damage, especially to the heating unit, which is central to autoclave’s function. You can check the mineral content (hardness/alkalinity) of the water in your area here. To avoid these issues, de-ionized (DI), or de-mineralized, water should be purchased or created by de-ionizing tap water using special equipment found in most laboratories. It is important to stress that this is not the same as distilled water, which only removes ionic impurities but does not change the mineral content.

Autoclaves also have different voltage requirements so your electricity source is another factor to consider. Some may need 220-240V (different to standard 120V outlets), which has the advantage of a faster heating time. Changing voltage requirements can usually be performed by a qualified electrician for a small fee.

Maintenance, Cleaning and Technical Support

As mentioned, autoclaves need regular maintenance for safety, proper functionality and minimal negative impact on your organization’s operation. But, if there is an issue with your autoclave’s operation, you should also ensure you have a reliable and quality technical support available. Purchasing from a large distributor could leave you on a waiting list and could also mean you have to deal with expensive technicians, though certain manufacturers do provide quality technical support that could also be free of charge.

One major aspect that should be considered when purchasing autoclaves is the chamber lid gasket, which differ in quality, longevity (frequency of changing) and price. Because of the intense heat and pressure that gaskets are subjected to, the gasket’s design and material quality is directly correlated with the frequency of which it must be changed.

Summary (The Bottom Line)

When choosing an autoclave, it is important to assess a variety of factors to make sure that the autoclave meets your organization’s needs. Including the autoclave’s capacity, throughput, space requirements, installation, maintenance, quality and costs over several years. Always make sure to consider not only factors such as selling prices, but long-term costs associated with the capacity / throughput, performance, and reliability that affect any organization’s bottom line.