Pre-vacuum autoclaves vs gravity autoclaves – Which type is best suited for medical facilities?


If you work in the healthcare industry, you’ve probably heard of autoclaves before. These steam sterilizer machines are becoming increasingly popular in all sorts of medical facilities, including dental and veterinary clinics, hospitals, and operating theaters.

They play a vital role in making sure that medical staff can operate in a safe working environment, and that infections don’t spread from patient to patient. This is thanks to their ability to rid medical tools and waste of any infectious foreign material.

The 2 main types of steam sterilizers present on the market are gravity and pre-vacuum autoclaves. In Celitron’s next article, we’ll help you decide which one is better suited for your medical facility!

How does a gravity autoclave work? How are they different from vacuum autoclaves?

Gravity autoclaves (also known as “gravity displacement autoclaves”) are the most common types of steam sterilizers available on the market. While they are less sophisticated than vacuum autoclaves, that doesn’t mean they are not a viable solution for certain medical facilities. They are used to treat smaller, more “basic” loads such as:

  • Flat surgical tools and lab utensils made of stainless steel
  • Polypropylene Pyrex® or Type I borosilicate glassware
  • Medical (red bag) waste
  • Unwrapped medical items

They are generally more affordable, which also explains their widespread presence. However, keep in mind that they are also slower than their most advanced counterparts, and less versatile. They can only treat medical items with a hard surface, and cannot be used to sterilize porous loads (i.e. permeable materials with small holes through which air can pass, like syringes or wrapped medical items).

The difference in performance and reduced versatility also lies in how they treat the materials which are loaded into the autoclave’s chamber. During the sterilization cycle, steam is pumped inside the chamber. This high-temperature steam will eventually rise to the top of the autoclave’s chamber, since it has a lower density than air, and gradually displace the air inside. The air then leaves via a drain vent.

By forcing the air out, this is how steam can make direct contact with the medical items inside. However, once the gravity cycle of the autoclave ends, the materials inside still need some extra time to dry and cool down.

There are 2 main types of gravity autoclaves:

  1. Class N autoclaves. The simplest models available on the market, are mostly used for flat materials with hard surfaces. They cannot remove all the air outside of their chamber.
  2. Class S autoclaves. A bit more versatile compared to the previous category, but still unable to treat materials made of textile.

How does a pre-vacuum autoclave work?

The presence of air is the greatest enemy of steam sterilization, as it can prevent the steam from thoroughly getting rid of all potentially infectious foreign materials present on medical items and waste. In gravity cycles, there a completely air-free environment cannot be guaranteed, which is why the steam can only treat certain parts of certain materials.

However, as their name implies, this is not an issue with pre-vacuum autoclaves – also known as “class B” autoclaves.

“Pre-vac” steam sterilizers like Celitron’s Azteca A or Azteca AC series use a powerful vacuum pump to dynamically remove all the air within their chamber. This allows the steam to penetrate the load inside almost immediately.

This enables vacuum autoclaves to treat materials such as:

  • Wrapped goods, surgical packs (which can trap air inside)
  • Pipette tips and other high-density polyethylene products, such as syringes
  • Cages with animal beddings at veterinary clinics
  • Media solutions in containers, such as tissue culture flasks with loose caps for a vacuum autoclave cycle
  • Medical textile items, such as textile-based PPE (Personal Protective Equipment) items

By increasing pressure inside their chamber, they can also increase the boiling point of water to over 100 degrees Celsius. With the temperature of sterilization cycles ranging between 121 and 124 degrees Celsius, Celitron’s vacuum autoclaves can kill any and all potentially infectious foreign materials present on dental tools and equipment, which can then be safely used again for the treatment of patients.

Pre-vacuum vs gravity: why does Celitron recommend vacuum autoclaves for hospitals and other medical facilities?

Pre-vacuum autoclaves can treat wrapped and unwrapped instruments, porous items, as well as medical textile products. This versatility is much needed in many medical facilities, especially hospitals that need to handle all kinds of materials for the treatment of patients.

Not to mention that having a vacuum pump also results in much faster sterilization and drying cycles, which helps staff work much more efficiently.

The benefits of using Celitron’s vacuum autoclaves for the sterilization of medical equipment and red bag waste

  • Capacities that suit medical facilities of all sizes. While we recommend larger hospitals and medical centers to opt for our previously mentioned Azteca AC and Azteca A medium and large models, Celitron can also provide smaller options with the Sting 11B Premium small vacuum autoclave.
  • Cost-effective and sustainable operation. With advanced water and energy-saving systems, Celitron’s pre-vac autoclaves allow your medical facility to reduce its operational costs as well as its environmental footprint.
  • Modern and easy-to-use technology. Thanks to a fully automated operation, medical staff can use our class B steam sterilizers without needing previous technical qualifications. Our autoclaves are also equipped with an LCD touch-screen display, facilitate maintenance with self and remote diagnosis capabilities, and make it easier to document your work with a PC connection.
  • Fast sterilization cycles. Once the process is launched with the push of a button, the load inside is sterilized, dried, and cooled down in about 20 minutes.
  • Extra safety features. While pressure and temperature levels still aren’t back to normal inside the vacuum autoclave’s chamber, its door cannot be opened.

There are many benefits to using vacuum autoclaves in the healthcare industry compared to gravity cycles. They provide a much-needed versatility for treating more complex medical equipment, not to mention they can be customized to suit the needs of small dental and veterinary clinics as well as large hospitals. Not to mention they are extremely user-friendly thanks to their automated technology.

Be sure to TAKE A LOOK AT CELITRON’S VACUUM AUTOCLAVES for more details and technical specs!

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