Autoclaves come in many shapes and sizes, as well as with different features that allow sterilization of different types of media, in different capacities and speeds.

Autoclave sterilizers are essential for almost any type of laboratory and it is crucial to choose the best autoclave that suits your needs.  Because autoclaves come in many shapes and sizes, from compact and portable to built-in wall units and many configurations from horizontal front-loading to top-loading autoclaves, it can be overwhelming to make the right selection and stressful wondering whether you have made the correct decision.

Choosing the best autoclave largely depends on several factors, including autoclave media (what you are autoclaving), your throughput needs (how large your autoclave media is and how much you need to autoclave) and available laboratory space, as well as convenience and personal preference.  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 primarily 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.  Gravity autoclaves are the most commonly used type on the market and are usually recommended for most cases, however, to determine the best type of autoclave for your sterilization media, you would need and the differences between gravity (steam sterilizers) and vacuum autoclaves please view the entry on gravity vs. vacuum autoclaves.

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, however, the effective chamber size is usually smaller than the actual chamber size, the extent of which depends on the configuration of the chamber and how the racks fit within.

Some items that need to be autoclaved can have unusual dimensions, so you want to make sure that these items fit in the actual autoclave chamber, given how the chamber is designed and how many racks fit into the chamber.  Not only is the capacity of the chamber (often measured in Liters) important, but one must consider the configuration of the autoclave chamber in order to determine whether the autoclave will meet your size needs.

As mentioned above, one must determine with certainty the exact capacity per cycle given the autoclave’s inner configuration.  Because the capacity for certain autoclave media is not readily available, make sure that you can contact the manufacturer to confirm their autoclave capacities.  For Tomy SX-Series autoclave capacity information, please indicate the type of media using TOMY’s contact form, or email at tomy@amuzainc.com and a representative will get back to you.

For most laboratories and start-ups, the best autoclave is one that does not require a huge autoclave that takes up a large amount of space, as well as plumbing, electricity and house steam, not to mention significant monetary and time investments for installation, and maintenance.  When looking at the price of an autoclave, it is always important to remember opportunity costs such as when an autoclave requiring a large amount of technical expertise breaks down.  These aspects will be covered further in this article, as they are quite significant and should be considered before making purchase decisions.

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.  In order 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) must be determined.  The best autoclave would be one whose throughput volume matches with the maximum throughput that your laboratory would require per day and per cycle.

Though the cycle time depends on the autoclaving media sterilization requirements, autoclaves have dramatically different warm-up and cool down times that can add to the overall cycle time.  Certain features, such as cooling fans can dramatically speed up this process, in some cases allowing for more cycles in a day and a higher throughput.  With the TOMY SX-Series Autoclave, the dual cooling fan system reduces the cool down time by up to 42%, saving approximately 25 minutes on the cool down time*, which can amount up to nearly two extra loads in a standard work day.

The type of autoclave that you choose can also dramatically make operations more efficient and one must consider the frequency of loads, the load size and the number of people accessing the autoclave.  Operations that require large and steady throughputs can greatly benefit from having several medium size autoclaves, whose use can be staggered, as opposed to large autoclaves that can leave people waiting and cause tremendous backup to the operation.  Having several smaller autoclaves can also be ideal in the event of a breakdown, as many backup autoclaves would be available, as opposed to having an operation completely shut down as a result.

Autoclave and Benchtop Space

You should assess the space that you have available in deciding what type of autoclave to purchase, as autoclaves come in many shapes and sizes, which respectively have advantages and disadvantages.  The best autoclave would be one that meets your throughput needs and keeps your operation going, without taking up any more space than necessary.

The most commonly found type of autoclave are front-loading autoclaves, which are designed with the cylindrical chamber sitting horizontally and open to a front-opening door.  Though seemingly convenient to have the chamber door open out toward the user, they are fundamentally wasteful in their use of autoclaving space for the following reasons:

1) Inside the box / outside the chamber– To start, autoclave chambers are fundamentally cylindrical due to physics, which require equal pressure throughout the chamber (cylinders are commonly used in autoclaves, as the round edges are less prone to high-pressure breaks than the corners of box-shaped containers).  Horizontal autoclaves are basically sideways facing cylinders enclosed by a box- with this design, the spaces around the outside of the chamber within the box are wasted.
2) Within the chamber– In front-loading autoclaves, items must have a flat surface on which to rest, which is 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 remainder is lost space.

One of the first lessons that you learn in pre-school is that the circular block does not belong in the square hole and vice versa.  This lesson applies in the case of autoclaves as well, as cylindrical chambers placed horizontally in front-loading square-shaped autoclaves are wasteful and do not make sense from a utilitarian standpoint.

Image result for children's circular square block toy

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

In summary, horizontal, front-loading autoclaves are fundamentally flawed in their design, as they take up significant bench space, and benchtop front-loading autoclaves take away space that could be used for other equipment or a clear working space for research.  Further, as space is lost outside of the chamber, inside of the chamber, and finally on the tray surface area, they are especially inefficient for their size, using an extremely small percentage of overall volume for autoclaving.  Considering these many factors, front-loading, horizontal chamber autoclaves are a literal waste of space.

On the other hand, top-loading autoclaves are the best autoclave for effectively utilizing space, as the vertical configuration of top-loading autoclaves and stackable baskets allow for the most efficient use the vertical cylindrical chamber.  Combined with the round-shaped sides, top-loading autoclaves can accommodate large capacities of autoclave media, which also tend to have round edges.  When considering an autoclave, always take into account the configuration and how this impacts capacity / throughput, as well as general laboratory space and efficiency.

Due to its top-loading design, round configuration and use of stackable baskets, the SX-700 autoclave can accommodate up to 27 300 mL flasks in one cycle.


Installation Utilities: Water and Electricity

Access to water is an important factor, as some autoclaves require plumbing, while others can function by simply adding water to the unit.  Many traditional autoclaves and those that have chamber vacuum functions tend to rely on an external water main or house steam in order to function.  While this setup allows for a steady source of water to feed the autoclave, it is physically limiting to need a designated space and setup for an autoclave.  Others, however, do not rely upon water or steam intakes and can function with water that is added to the autoclave chamber.  The TOMY SX-Series Autoclave does not require any plumbing or installation and simply needs to have water added periodically in the chamber.  One just needs to make sure to use the proper mix of DI (De-Ionized) water (not to be confused with distilled water), combined with a small amount of tap water, as the autoclave senses water through ion detection.  More information on proper water use can be found in the following entry on autoclave maintenance.

Autoclaves also have different voltage requirements so your electricity source is another factor to consider. Some may require 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.

A model from the TOMY SX-Series can be placed anywhere there is a power outlet, and no plumbing or installation is required. All you need to do is plug in your autoclave and add water.  The chamber layout within the autoclave is also a factor to consider as vertical autoclaves have stackable baskets that are ideal for maximizing space.  The TOMY SX-Series also has a top-loading design, which offers a small footprint and other innovative features that will save you valuable laboratory space as it can be placed either on the bench or your floor space.

Maintenance, Cleaning and Technical Support

As mentioned, autoclaves require regular maintenance for safety, proper functionality and minimal negative impact on your organization’s operation.  However, if there is an issue with your autoclave’s operation, you should also ensure you have a reliable and quality technical support available.  Most come with a one-year warranty, though you should check your manufacturer’s paperwork to check these terms. 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.

Autoclaves also require regular maintenance and part replacement in order to continue functioning properly and to extend the life of your autoclave.  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.  Consequently, gaskets that require more frequent changes will add to the maintenance costs of your autoclave- some autoclaves require monthly gasket changes, which can hundreds per change require several thousand dollars in a matter of years.

Poor quality gaskets can cost your organization thousands of dollars in a matter of years, however, TOMY SX-Series autoclaves come with thick and sturdy, high-quality gaskets that require changing only once every 3 years, depending on frequency of use.  One would agree that an autoclave that does not require frequent part changes that are costly to maintain are best.  Because the TOMY SX-Series gasket requires significantly less changing and much lower costs than those of competitors, this factor alone takes thousands of dollars off autoclaving costs and should be considered when making a purchase decision.

Thick and sturdy, high-quality gaskets for the TOMY SX-Series can save your organization thousands of dollars over several years

The ability to easily clean your autoclave should be seriously considered, as a major source of damage to autoclaves, especially autoclave heaters, is dirty water that sits in the autoclave chamber.  At high temperature and pressure, impurities that get into the water from autoclave media can stick and burn to the autoclave heater, preventing the heater from transferring heat and permanently damaging it, potentially rendering your autoclave obsolete.  For TOMY SX-Series autoclaves, water in the autoclave chamber can be drained by removing the white plug and opening the drainage valve (green handle) under the machine and draining this into a container for disposal.  For biohazardous material and water disposal, especially for BSL (Bio Safety LeveL) 2 and above laboratories, please contact the Center for Disease Control or the relevant national authority for disposal instructions.

The TOMY SX-Series easily accessible vertical cylindrical chamber allows for easy cleaning that prevents damage and extends the life of your autoclave.

Finally, it is important to choose a reputable company for recognized quality and craftsmanship products.  TOMY still has its manufacturing operations in Japan and its products are known to provide quality and long-lasting reliability.  TOMY also offers worldwide technical support and parts through distributorships, which means this is a wise decision to purchase through them to ensure your peace of mind.  Always check your service agreement and ensure that your autoclave meets the specific industrial standards (such as ISO standards) and guidelines for your organization’s in-house standards.

Summary (The Bottom Line)

When choosing an autoclave, it is important to assess a variety of factors to make sure that the autoclave is a best match for your organization’s needs, including the autoclave’s capacity, throughput, space requirements, installation, maintenance, quality and overall costs over several years.  One may find that pre-existing alternatives do not meet modern and ever-changing needs of your organization, whether a public institution or a smaller start-up that demands a versatile, high quality and reliable autoclave to keep the organization running smoothly.  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.

If you have any questions about autoclave features, repair or maintenance, or you need more specific advice as to whether TOMY autoclaves would meet your organization’s unique needs, please email us at tomy@amuzainc.com, call us on 858-800-3900, or contact us using the Tomy Amuza site contact form.

*Save up to 25 min on autoclave cycle time with the Tomy SX-Series dual fan cooling system, which reduces chamber cooling temperature from 121°C to 60°C from 59 minutes to 34 minutes.

Tomy SX-Series Autoclave Sterilizer

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