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Autoclave Sterilization Process Guide

Autoclave Sterilization Process Guide
January 11 , 2022

What is an autoclave used for?

An autoclave chamber sterilizes medical or laboratory instruments by heating them above boiling point. Most clinics have tabletop autoclaves, similar in size to microwave ovens. Hospitals use large autoclaves, also called horizontal autoclaves. They’re usually located in the the Central Sterile Services Department CSSD) and can process numerous surgical instruments in a single sterilization cycle, meeting the ongoing demand for sterile equipment in operating rooms and emergency wards.

tabletop autoclave

Small Autoclave, also known as tabletop autoclaves, can be found in dental offices

Generating Steam and Steam Quality
Steam is the autoclave’s sterilization agent. In our Sterilization Methods series, we explained the physics of steam and why it’s ideal for destroying microorganisms such as bacteria and spores. Part 1 of this post will explain how steam is generated for autoclaving purposes. Part 2 in this series will discuss the various types of autoclave steam supply and generation and when each is used.

Back to the Source
The ANSI/AAMI sterilization standard states:
There are two common sources of steam used for sterile processing: hospital steam boiler systems and self-contained electric boilers. In both cases, treated water supply is necessary to remove total dissolved solids (TDS). Each system should be designed, monitored, and maintained to ensure that the quality, purity, and quantity of the steam provided are appropriate for effective sterile processing

HouYuan Medical provides autoclaves that connect to the building or hospital steam supply as well as models equipped with self-contained electric steam generators. Other HouYuan autoclaves are fitted with a double-steam option (capable of changing steam supply source according to building steam availability) fitted to user requirements. The autoclave steam generator is either built-in or stand-alone, depending on chamber size.

Autoclave Steam Quality
When it comes to transferring large quantities of energy to an object requiring sterilization, nothing’s more powerful than steam. After all, steam engines propel ships and trains. Even the Titanic was powered by steam.

We discussed steam quality in a detailed post on sterilization methods, but let’s review the factors that determine this quality, because it’s crucial for proper autoclave functioning and the sterilization process as a whole. Two parameters are most important:
* the level of non-condensable gases
* the moisture level

Dry Steam? Wet Steam? Not in the Autoclave
Less than 3% humidity produces what’s called dry or superheated steam. This steam increases sterilization time because it reduces energy transferability. Superheated steam lowers humidity to roughly 0%, transforming the autoclave to a dry-heat oven. The energy transfer is reduced, and what takes three minutes in an autoclave at 134°C takes two hours at 160°C and thirty minutes at 180°C!!

However, greater than 3% humidity generates saturated or wet steam, which requires higher sterilization pressure and temperature. Wet steam also extends the drying time at the end of the sterilization process. A dry load is required at the end of the process when the load is wrapped and not intended for immediate use.

Autoclave sterilization standards and directives permit some flexibility in steam humidity levels, since it’s almost impossible to supply perfect steam at a steady flow. Even if conditions are nearly optimal, many variables affect steam as it’s transferred to an autoclave. Chief among them: weather conditions and temperature; piping quality, length, and structure; drainage stations; and availability of high-quality steam traps.

More about HouYuan autoclave sterilizers:

* Medical autoclaves like tabletop autoclaves and large horizontal autoclaves

* Dental autoclaves - ideal sterilizer for dentists

* Laboratory autoclaves like vertical autoclaves

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