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Autoclave types / sterilizer types

Autoclave Types - what is the best autoclave type / sterilizer type for my healthcare setting?

This post has been written with a view to helping medical professionals and medical procurement staff get a deeper understanding of the different autoclaves machine types and their use, to help you make an informed choice when considering your next purchase.

Here we have detailed information about what an autoclave is, its functions in a medical environment, and the different types of autoclaves and sterilizer types available in the market. We will also consider the different autoclave types that are most suitable for the specific medical settings you are working in, as well as what the future of autoclaves looks like, and what advancements you can expect to see in the coming years.

If you are currently in the process of planning to replace your autoclaving system and are looking for the right advice and suggestions, keep reading. Here we will review the entire autoclave market, enabling you to make the right decision about the autoclave type you should purchase for your healthcare facility.

What is an autoclave?

Autoclaving is a sterilization method that uses high-pressure steam to sterilize medical equipment. The autoclaving processes work on the concept that the boiling point of water (or the steam) rises when it is put under high levels of pressure.

The history of the autoclave

The term “autoclave” is derived from the Greek word for “auto”, meaning self, and the Latin word “clavis”, meaning key. So, in short, an autoclave refers to a self-locking device. It is commonly used in medical settings to sterilize equipment to reduce the risk of infections and contamination.
The first autoclave was actually a pressure cooker. It was originally invented in around 1681 by Denis Papin, who was a French physician, as a way of preparing food. He called this invention a "steam digester" and described how the processing of food using this device could improve digestion. The autoclave was later re-invented in 1879 by Charles Chamberland for scientific and medical purposes.

The primary purpose of an autoclave

The items or medical equipment to be autoclaved are subjected to a gradual rise in temperature under specific conditions such as high pressure until a temperature of 121 °C is attained. It is then steamed for about 15 to 20 minutes.
The autoclave device allows steam to flow around the items and equipment in the chamber. The temperature and the duration of time necessary for sterilization to occur depend on the items and whether they are left exposed to the steam or are wrapped. The items must be separated to ensure that the steam can penetrate the load in an even manner. The steam should reach the small crevices and kill all bacteria, bacterial spores, and viruses thus sterilizing the equipment thoroughly.

Autoclaves can be used to eliminate or destroy microorganisms, vulcanize rubber, cure composites, and perform hydrothermal synthesis. It offers a highly dependable method for the decontamination and sterilization of laboratory glassware, reagents, medical instruments, and other waste media. Autoclaves can also inactivate spores, viruses, fungi, bacteria, and other microorganisms that may have accumulated on surgical instruments including scalpels, scissors, and forceps thereby reducing the risk of infections when these instruments are used during patient treatments or surgeries.

What are the different autoclave types and sterilizer types?

Gravity displacement autoclave
Gravity displacement autoclaves are the most common type of autoclave that rely on the use of dense steam in order to force the air out from the chamber of the machine. They are more suitable for the treatment or sterilization of basic loads such as flat surgical tools and some forms of bio-hazardous waste, though they are not as versatile as pre-vacuum autoclaves.

High-speed pre-vacuum sterilizer
High-speed pre-vacuum sterilizers, also called the prevac (pre-vacuum) autoclaves, are the types of autoclaves that use a vacuum pump for removing all the air from the chamber of the device, allowing for the better penetration of the steam.
These devices help in the sterilization of complex loads and materials including medical textile products, larger pieces of equipment, and porous loads. They can also be used to sterilize objects that are made of high-density polyethylene such as the pipette tips and syringes of sharps.

What are the different classes of autoclaves?

Class B - positive pressure
Class B autoclave is a compact autoclave. However, its performance level is comparable to that of the largest autoclaving machines used in hospitals. The letter “B” stands for the “big small sterilizers”, as they are small machines offering bigger performance.
Any form of load can be processed and sterilized in a class B autoclave. These include porous materials, textiles, products in pouches, and hollow items like wands, tips and turbines.
The applicable standard for an autoclaves of this type is EN 13060 that is specifically dedicated to small steam sterilizers (machines with a sterilization chamber which is smaller than a sterilization unit). This standard helps to distinguish between the sterilization cycles based on the materials that are being sterilized such as type A solid load, having hollow sections, solid loads, or type B solid loads, having hollow sections.
Class B autoclaves are suitable for a broad range of settings. They are considered the most suitable autoclave machine for dental practices as they offer a higher degree of flexibility. Also, though these devices are smaller in size, type B autoclaves offer outstanding performance, the highest possible safety standards and an unbeatable efficiency.
The strengths of these devices include the ease of handling due to their ergonomic designs and extensive energy savings due to lower power consumption. The user-friendly type B sterilizers are considered the most efficient as far as maintaining safety and hygiene in a medical environment is concerned. Moreover, they also provide a higher level of practicality.

N Class Autoclave - pressure cooker
The N class autoclaves are small and compact devices that are commonly used for sterilizing simple medical equipment and materials. The alphabet “N” stands for “naked solid products”. So, these autoclaves can not be used for the sterilization of textiles, hollow items, porous loads, and any product in pouches, because the cycles do not have the characteristics that pass the specific physical tests.
Also, another potential downside of N type autoclave is that it can not guarantee the steam penetration required for optimum sterilization of equipment, which is dependent on the creation of the vacuum at the beginning, which is not mandatory for these machines.

Class S - negative pressure
The class S autoclaves cover all other forms of autoclaves. These are essentially an intermediate class of autoclaves between the type B and type N autoclaves. Its characteristics are not clearly defined by any specific standards. So, only the manufacturers are able to provide all the details of the performance capabilities of these devices, as established by specific tests.

Gravity displacement

Vertical autoclaves
This type of medical autoclave can be loaded by opening the lid at the top. These are especially suited for smaller clinics with cramped spaces or in laboratories. They also have a comparatively smaller capacity chamber making them suitable for clinics where space is a constraint.

Horizontal autoclaves
These are front-loading steam sterilizers with a larger capacity chamber. When the space available in your clinic or hospital is not an issue, and if you need to treat or sterilize multiple loads every day, the horizontal autoclaves provide a superior way for reducing the strain on your medical staff.

Which autoclave is the best for my workplace?

In order to find the type of medical autoclaves that will be best suited to your healthcare facility, we need to consider the specific environment of your clinic, laboratory, or hospital, and your primary requirements.

If a large share of the medical devices you need to sterilize comprises flat surgical tools and biohazardous waste, you could opt for the gravity displacement autoclave. On the other hand, the prevac (pre-vacuum) autoclaves may be suitable for you if you need to sterilize a large amount of complex loads comprising medical textile products, larger pieces of equipment, and porous loads. These autoclaves are also suitable for your clinic if you need to sterilize equipment and materials made from high-density polyethylene such as the pipette tips and the syringes of sharps.

You could choose a vertical autoclave if your clinic or laboratory is small and your autoclaving needs are not extensive. These autoclaves are suitable if you do not have to sterilize equipment several times a day or a week and if the autoclaving loads are not large.

Horizontal autoclaves are perfect for larger clinics and hospitals where the medical staff are already burdened with a lot of responsibilities. These autoclaves can handle a larger load thus saving the precious time of your staff.

What is your primary requirement?

Speed and cycle times vary among different autoclave types and cycle parameters, and so do the warm-up and the cooling times. If you want to get your equipment sterilized quickly, you may choose smaller autoclaves that have a faster speed. If you sterilize equipment only once or twice a day and have spare equipment ready for use in times of emergency, you may decide to opt for the larger autoclaves.
The autoclaves with quicker cycles provide rapid reprocessing of equipment and a faster availability of the device for the subsequent loads.

Small steam sterilizers having a chamber size of up to 60 liters as well as the vertical autoclaves are suitable for use in small hospitals and dental clinics. It is also important to pre-designate and design a space in your clinic for an autoclave in order to improve the future efficiency and performance. The autoclave you choose must fit into the designated area in the processing room, whilst still allowing for set-down areas.

You also need to consider the cycle times and load capacity and ensure these parameters are not compromised when buying a smaller autoclave for saving space.
Also, if you have or anticipate a very high throughput of medical instruments, it may be helpful to have two smaller medical autoclaves instead of buying one large autoclave, depending on the available space.

This offers several potential advantages such as:
  • Smaller autoclaves need less energy compared to larger autoclaves
  • Flexibility while processing smaller loads
  • Accommodation of anticipated growth in the future
  • Potential for staggered loads and simultaneous use
  • The availability of a back-up allows you to reprocess instruments (though fewer) in an uninterrupted way when one autoclave is out of service and in times of emergencies.

Environmentally friendly

Most hospitals and clinics are making careful and responsible choices to ensure the autoclaves they choose are environmentally friendly. If you are conscious of the impact of autoclaves on the environment, you may choose those that are designed for minimizing energy expedite and reducing noise emissions.

Large-volume autoclaves

You need to consider the volume of the instruments to be sterilized on a daily or a weekly basis when choosing the most suitable autoclave for your healthcare facility. You should consider the number of instruments you use per day, and how often they are needed.

Some other parameters to consider include the types of instruments that need to be sterilized, the number of and pieces you use daily, and whether any instrument require a dedicated cycle.
You may purchase larger autoclaves if the number of instruments, the bulk of instruments, or the frequency of sterilization is more. Otherwise, you could opt for a smaller autoclave. Smaller autoclaves are also suitable when some of the instruments require a dedicated cycle.

What is the future of autoclaves?

There are research studies being conducted to evaluate the impact of autoclaving on the environment and design ozone-generating sterilizers. These autoclaves are proving easy to operate, compact, and cost-effective in both industrial and hospital settings.

Ozone sterilization is believed to be safer for the environment as it does not involve any toxic chemicals or harmful emissions.

There is also a focus on designing medical autoclaves that also serve as waste converters and offer simpler and safer solutions for sterilizing medical equipment more efficiently without creating an adverse impact on the environment. There is an emphasis on designing and manufacturing autoclaves that are less complicated, have no pressure vessel, and include advanced features like the closed-loop water cycle.

Moreover, there are also attempts being made to design solar-powered autoclaves that are considered safer for protecting the environment by ensuring zero hazardous waste footprints.

Popular autoclave models

Some of the main autoclave models available on the market today include:

Tuttnauer 1730
Midmark M11
Midmark M9
Tuttnauer 2340m
Tuttnauer 2540m
Tuttnauer EZ10
Tuttnauer EZ11Plus
Tuttnauer 3870ea

You can find additional information on these models by clicking on the links above.


There is a wide range of different types of autoclaves available in the market. Choosing the best autoclave for your specific working environment is imperative for maximizing efficiency and cleanliness.
If you would like additional advice on the most suitable autoclave for your workplace, contact our specialists today on or call 1 (888) 228-7564