Last Updated on May 1, 2023
Types Of Autoclaves
The way that autoclaves work varies depending on whether they use gravity or vacuum-induced or pre-vacuum (pre vac) sterilization methods. That said, there are some autoclaves that use both methods to sterilize. Both types of autoclaves sterilize through high-temperature steam and the chamber becomes pressurized, so it does not release any air in the chamber which helps heat penetrate all parts of what is being sterilized. The mechanisms differ and this article will outline how these two kinds of systems operate with different media associated with each type respectively.
Gravity autoclaving, also known as gravity displacement autoclaving, is the most basic form and is suitable for sterilizing the most common laboratory media. This includes steel utensils, glassware, and bio-hazardous waste. Gravity-induced autoclaving involves pumping steam into the autoclave chamber. Which displaces the ambient air and forces it out of exhaust valves so that the remaining steam can sterilize the contents. This mechanism is helpful in the simplicity of its design and lack of dependency on peripheral mechanisms to displace ambient air with steam. Making these types of autoclaves more affordable and dependable.
Most autoclave media or items to be sterilized are simple in design and do not contain spaces or obstacles for steam to penetrate within, thus the steam displacement function is ample for proper sterilization. It is for these reasons that gravity autoclaves are the most common types of autoclaves in the market and are usually the recommended type of autoclave for most uses.
Vacuum autoclaving, also known as pre-vacuum autoclaving or sterilizing, is more suited where air cannot be easily removed from sterilization media. This may include large or porous items such as animal cages and bedding sterilization as well as wrapped surgical kits. The vacuum function in these autoclaves allows deeper sterilization of the contents, as it completely evacuates the ambient air within, allowing high-temperature steam to penetrate and sterilize areas that would normally be occupied by ambient air, and can be more efficient at sterilizing certain items with hard-to-reach areas within.
Autoclave Media & The Corresponding Autoclave Type
As mentioned above, your choice of an autoclave system largely depends on your autoclave media, ie. the items to be sterilized. Overall, steam sterilization is highly dependable, effective, fast, and non-toxic, and offers an inexpensive way to rapidly heat and penetrate the chamber’s contents, including appropriately contained liquids. However, this method cannot sterilize powders or oils, and can only work with heat and moisture-resistant goods. Keeping this in mind, below, I summarize the primary media used by gravity and vacuum-autoclave types.
Gravity autoclaves are appropriate for sterilizing non-porous items (i.e. those with a hard surface):
- Most metals, particularly stainless steel surgical instruments and lab utensils
- Polypropylene Pyrex® or Type I borosilicate glassware
- Biohazard waste
- Unwrapped goods
Vacuum (pre and post) are appropriate for sterilizing large or porous items:
- Media solutions in containers, such as tissue culture flasks with loose caps for a steam autoclave cycle
- Pipette tips and other high-density polyethylene products, such as syringes
- Wrapped dry items that can trap air
- Animal cages and bedding
Choosing An Autoclave
Choosing the right autoclave for your purposes requires you to not only assess the type of media to autoclave but also throughput capacity, available lab space, and access to utilities, including electricity (with proper power output), water, and house steam.
Because of the simplicity of the gravity-displacement mechanism, which requires an autoclaving chamber, a heating mechanism, intake, and exhaust valves, there is great flexibility in the design for gravity autoclaves, including front and top-loading types.
The top-loading type autoclave is helpful, as it allows for maximum loading space, minimum floor space requirement, and does not require any building steam connection, as the vertical chamber design allows for water to rest at the bottom, which is turned into steam through a heating element at the bottom. Note that many autoclaves on the market, especially compact top-loading autoclaves, often require only access to the proper electrical outlet type and enough space to place your autoclave.
Gravity autoclaves are also particularly helpful when used in geographical areas of high humidity or higher altitudes. As they consistently keep the relationship between pressure and heat within the autoclave chamber and overcome differences in boiling points at higher altitudes by opening and closing the exhaust valve. Known as high altitude autoclaves, their functions allow for proper sterilization to occur in laboratories and hospitals in markets with high altitude terrains.
Regarding the size of your autoclave, to limit energy use and costs, especially for smaller labs, it is important to buy the proper size autoclave that will accommodate the equipment that needs sterilizing, while not going overcapacity. For this, several autoclaves range between 50 L and 70 L, which strike a good balance between relatively high capacity and low energy use.
For more information on autoclaves that may be the right match for your laboratory,
please fill out a contact form and one of our sales representatives will get back to you shortly.
Can you tell me or point me in the right direction for documentation for all the different terms used for vacuum sterilizers? Gravity sterilization generally is a much longer cycle. We have Pre Vac and Steam Flush Pressure Pulse in our hospital. The issue we have is when looking at Manufacture’s Instructions for Use they have many different terms for vacuum sterilizers. For example: Pre Vac, Dynamic Air Removal, Fractioned Air, Steam Vacuum. can we assume that any vacuum type sterilizer would be interchangeable with the time and temp directions from manufacturers? For example: Gravity method 20 minutes at 250 degrees F. Pre-Vac method: 4 minutes at 270 degrees F.
thank you for your inquiry.
Regarding terminology for vacuum-driven steam sterilization technology, the most common terms are “vacuum sterilization” “pre vacuum sterilization” and derivatives of these terms. There are several other less common terms that are used, including the ones that you mentioned, as manufacturers often use alternative product descriptions to distinguish their products from others. However, the “vacuum” and “prevacuum” are most commonly used. Please note that SFPP (“Steam Flush Pressure Pulse”) is also classified as a type of dynamic air removal along with vacuum or pre vacuum autoclaves by the AAMI (Association for the Advancement of Medical Instrumentation), but have slightly different functionality than vacuum/pre vacuum autoclaves.
For more information on steam sterilization in healthcare facilities, please refer to the AAMI Comprehensive Guide to Steam Sterilization and Sterility Assurance in Health Care Facilities.
Hi , how long does it take to complete a sterilisation run (time from start to finish)?
Thank you for your inquiry.
Though total sterilization cycle time varies depending on sterilization temperature, time, and the sterilzation environment (temperature) for a typical setting of 20-minutes at 121°C, the total cycle time is around 70 minutes including heat up and cool down time.
If you have any questions, please email us at firstname.lastname@example.org or call us at 858-800-3900.
Can an autoclave reach a temperature of 280 degree Celsius? If yes, please specify.
thank you for your inquiry.
The maximum temperature that TOMY autoclaves can reach is 135°C (or 275°F), as sterilization is typically carried out at between the standard 121°C and 134°C.
Please refer to our product page for other specifications and download product information: https://tomy.amuzainc.com/autoclave/
Are Tomy autoclaves the gravity type?
thank you for your inquiry- yes, the Tomy SX-Series Autoclaves are a gravity displacement type steam autoclave sterilizers.
You can find out more info about Tomy SX-Series Autoclaves here: https://tomy.amuzainc.com/autoclaves/
When is the vacuum function applied in an autoclave..Is it before the sterilisation hold or after the sterilisation hold or in between sterilisation hold temperature…?
thank you for your inquiry.
In most vacuum autoclaves, the vacuum function is applied first to remove the air in the chamber and then steam is added until the target temperature and pressure is achieved to start the cycle.
In gravity autoclaves or gravity displacement / downward displacement autoclaves, the pressurized steam does the work of pushing out and replacing the ambient air until the chamber is saturated with steam. The autoclave shuts its valves and allows the pressure to build until the target pressure and temperature is achieved, at which point the cycle starts.
If you have any further questions, or are interested in learning more about autoclaves, please contact us at email@example.com, or fill out the contact form and we will get back to you soon.
Thank you for visiting,
The TOMY Team
Hello sir, I would like to know which autoclave will be best for sterilization of dental equipments,,,, gravity or vacuum and also whether front loading or top loading? And also what are their prices
thank you for reaching out with your question.
For dental equipment, if you are using sterlization pouches, you would likely want to use a vacuum autoclave to allow the steam to penetrate the pouch and sterilize the contents within.
Please have a look at the video on this page. You can access it in this link <https://tomy.amuzainc.com/blog/types-autoclaves-gravity-vs-vacuum-autoclaves-advantages/>.
Thank you and all the best in your autoclave search!