Autoclave / Steam Steriliser of Class B and Class S | MELAG


MELAG Medizintechnik GmbH & Co. KG
Geneststraße 6 -10
10829 Berlin
T +49 30 75 79 11-0
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Autoclaves and steam sterilizers for practices and clinics

Class B and Class S steam sterilization in compliance with international standards

A safe and efficient reprocessing workflow provides protection for patients and clinic personnel alike. Steam sterilizers and autoclaves are a prerequisite for a reliable instrument decontamination workflow in practice and clinic context.

With the European standard EN ISO 13060 a new classification system was enforced for steam sterilizers and practice autoclaves, specifically classifying Class S and Class B units. Tailored to the needs of practices and clinics, MELAG provides autoclaves of both classes while ensuring the highest level of quality and reliability. Worldwide sales of over 500.000 steam sterilizers and autoclaves are proof of the international success and appreciation of the MELAG product line. Since the founding of the company in 1951, MELAG established an impeccable worldwide reputation and has set new standards in instrument decontamination with the innovative solutions.

Discover our product highlights of the MELAG autoclaves for steam sterilization:

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What is an autoclave / steam sterilizer?

A sterilizer can achieve the destruction of all pathogenic organisms using heat, pressure or radiation. International hygiene guidelines recommend using autoclaves, which perform sterilization of medical devices and instruments with saturated steam. Autoclaves are widely used in dentistry, medicine, podiatry, tattooing and veterinary medicine. The units for steam sterilization vary in size and function depending on the instruments intented to be sterilized.

The terms autoclave and steam sterilizer are often used interchangeably. Steam sterilizers are defined as gas-tight sealable pressure vessels for the thermal reprocessing of materials requiring elevated temperature and pressure different from ambient air pressure. The temperature of the saturated steam in combination with the holding time ensures successful sterilization of medical instruments, textiles and other medical devices. The steam sterilization is usually performed at 134 degrees. Fractionated pre-vacuum is applied multiple times to evacuate air from the sterilization chamber ensuring the decontamination of complex hollow body instruments, such as endoscopes, dental hand pieces and ultrasonic suction cannulas.

Learn more about the correct use of autoclaves in our video tutorials:

Watch now


The steam sterilization process

The difference between Class B and Class S autoclaves

International hygiene guidelines recommend that instruments are wrapped and sealed after cleaning and disinfection and then sterilized - preferably with saturated steam. Packaging the instruments in sterilization pouches or in sterilization containers prevents recontamination of the instruments after the sterilization cycle.

The European standard DIN EN ISO 13060 divides autoclaves into the classes B, S and N.

The following section presents the entire cycle of steam sterilization (in general) in an autoclave:

  1. The pre-conditioning phase: Air inhibits sterilization and must be removed from the chamber and the hollow bodies of instruments. The pre-conditioning phase comprises a conditioning and (as required) an evacuation phase. Steam is injected during the conditioning phase generating over-pressure in the sterilization chamber. The Class B or Class S steam sterilizer then evacuates the resulting air-steam mixture. This process is repeated in the autoclave up to three times. The air removal phase ensures that no air remains in the sterilization chamber and the inside of hollow body instruments.
  2. The heating phase: The continuous introduction of steam generates a pressure and temperature increase in the sterilization chamber.
  3. The sterilization phase / exposure phase: The sterilization phase starts as soon as the program-specific sterilization parameters have been achieved. Typically, the load is exposed to a set temperature of 134 degrees °C for a plateau time of 5.5 minutes. Heat or moisture-sensitive instruments and textiles can be sterilized using the Gentle-Program with a temperature of 121 °C for a holding time of min. 20.5 minutes.
  4. Pressure release phase: Pressure is released from the sterilization chamber through an exhaust valve after the holding time is reached.
  5. Drying phase: Depending on what sterilization method is used, the instruments and packaging are dried using either vacuum drying or high-pressure drying.
  6. Ventilation / exhaust phase: Upon completion of the sterilization program, autoclaves using Class B or Class S programs draw ambient air into the steam sterilizer chamber through the air filter, thus the sterilizer chamber is exhausted to atmospheric pressure. It is now possible to open the steam sterilizer door and remove the reprocessed instruments.

MELAG Class S and Class B autoclaves provide the most reliable steam sterilization solution for all medical fields. The next section explains the differences between these two classes.

Class B autoclave with sterilisation process graphic

Class B sterilization:

Class B autoclaves enable the sterilization of both wrapped and unwrapped instruments, no matter their type and complexity. The fractionated vacuum reduces the air in the sterilization chamber through repeated evacuation and steam injection. This process permits the sterilization not only of solid and porous instruments, but also of complex hollow body instruments with narrow lumen such as surgical hand pieces and endoscopes.

A standardized helix test body can be used to check the successful steam sterilization, even of complex hollow body instruments. Our Class B practice steam sterilizers use the same advanced technology as large autoclaves in hospitals and CSSD.

All MELAG Premium-Class, Pro-Class and Cliniclave autoclaves work according to the Classe B process.

Find out more about our Premium-ClassPro-Class and Cliniclave Series

Autoclave Class S with sterilisation process graphic

Class S sterilization:

The Class S steam sterilization ensures the decontamination of single and double wrapped instruments, porous products and small parts. The MELAG high-performance vacuum pump is even able to sterilize simple hollow body instruments such as hinged instruments (scissors, clamps). The user manual of your Class S steam sterilizer provides a comprehensive overview of the proper and intended use.

If you do not use complex hollow body instruments, we recommend to prefer a Class S steam sterilizer over a Class B steam sterilizer. The cost-efficient Class S autoclaves either use the method of gravity displacement or a simple fractionated pre-vacuum.

MELAG Class S autoclaves of the Euroklav and MELAtronic series provide reliable and safe sterilization for practices and clinics using solid and simple hollow body instruments.

Find out more about our Class S steam sterilizers of the Euroklav and MELAtronic Series

 Steam Sterilization of hollow body instruments

Stand-alone autoclaves vs. devices with a fixed water connection

The best technology for your decontamination room

Whether you choose a stand-alone device or a steam sterilizer with a fixed water connection, MELAG has the best solutions to meet all requirements in your decontamination room:

The stand-alone autoclave gives you the opportunity to be flexible and location-independent. The only pre-condition is an electrical power outlet in your decontamination room. As there is no additional installation required to ensure the water supply, demineralized water is to be manually filled into the integrated water tank of the autoclave. MELAG stand-alone steam sterilizers are fitted with high-performance air-cooling of the membrane pump to guarantee the reliable use during non-stop operation.

Learn more about filling and emptying stand-alone autoclaves / sterilizers in practice in our video tutorial:

Video tutorial for stand-alone autoclaves

Autoclaves with a fixed water connection save both time and money through the automated supply of high-quality demineralized water. These steam sterilizers require feed water and waste water connections. A small amount of tap water is reprocessed with a water treatment unit to be used for steam sterilization. The other fraction of tap water is used for effective cooling of the vacuum pump and other components.

High-quality demineralized water is very important for decontaminating instruments in a medical or dental practice and clinic. Low water quality can result in deposits building up on the instruments and in the sterilization chamber.

The combination of the MELAG autoclaves with a MELAdem water treatment unit ensures comprehensive instrument protection and value-retention of the steam sterilizer. The time-consuming acquisition and disposal of aqua dem canisters is not more than a distant memory. MELAG provides every practice and clinic with individual system solutions for the entire instrument decontamination process. An overview of the complementary water treatment units is available here

Learn more in our video tutorial about the correct filter exchange procedure for the MELAdem 40 water treatment system:

Video tutorial for fixed-water connection autoclaves


Decontamination room with Autoclave

Frequently Asked Questions

Which requirements are placed on the demineralized water for steam sterilization?

The terms distilled water and demineralized water are often used interchangeably. Whilst distilled water requires reprocessing through evaporation and condensation, demineralized water refers to water, which does not contain minerals. However, the achieved water quality using the respective methods can be the same. Demineralized water is usually produced in water treatment units using ion exchange or reverse osmosis.

The requirements placed on the demineralized water are defined in European standards DIN EN ISO 13060 and DIN 285. A reference on the labels of the aqua dem container provides reassurance about the suitability of the demineralized water for the sterilization process.

Please fill the demineralized water in the integrated water tank of the stand-alone autoclave. The water quality is checked before every program start using conductivity measurement. With a water quality of 40 µS/cm, the steam sterilizer issues a warning; a malfunction message is issued if 60 µS/cm is exceeded. If the tank of the autoclave contains water of insufficient quality, the program start is disabled. The abbreviation “µS/cm” stands for micro-Siemens per centimetre. This value defines the electrical resistance of the solution between two flat or cylindrical electrodes separated by a fixed distance.

Medical and dental practices or clinics are confident with MELAG autoclaves using an automatic feed water supply. We recommend the water treatment units of the MELAdem series for this purpose: The MELAdem 47 uses the reverse osmosis method while the MELAdem 40 and MELAdem 53 use the ion exchange method. Reprocessing the tap water produces optimal demineralized water with conductivity between 1 and 5 µS/cm.

Which costs are due in the operation of an autoclave?

International hygiene guidelines specify the performance of maintenance services to guarantee the reliable operation of the steam sterilizers. Only technicians with requisite training may be entrusted with performing this service task. Steam sterilizers and washer-disinfectors are usually equipped with maintenance counters, which issue a maintenance message after completing a specified number of cycles or time interval.

Other manufacturers of autoclaves use different maintenance sets and spare parts. During the product development stage, MELAG places considerable value on sustainability, thus aiming to minimize the number of spare parts for later maintenance while also reducing service times. The most important maintenance task performed on MELAG products is the inspection of all relevant components ensuring the functionality of the device, as well as the replacement of wear parts.

MELAG-trained technicians perform the maintenance measures quickly whilst seeking to minimize costs. The obvious advantage of using the MELAG system solution is that the maintenance can be performed quickly and most of the time in one sitting. However, the associated cost-savings are not achieved when setting up a multi-brand decontamination workflow that requires different service technicians to carry out inspection at different times of the year on different devices. MELAG offers a hassle-free, co-ordinated and cost-friendly alternative.

In addition to maintenance costs, the consumption costs for energy and water drive up the cost of steam sterilization. MELAG engineers attach significant importance to achieving low consumption figures without a loss in quality. Additional costs can also result from unforeseen repairs of the autoclaves. MELAG stands for quality “Made in Germany”. Our entire product range is produced exclusively in Berlin. With over 160 R&D, IT and testing engineers, we strive daily to improve quality. MELAG products have developed a reputation for being reliable, user friendly and low maintenance. Taking into consideration all the costs incurred throughout the devices life span, the total cost of ownership of MELAG devices is significantly lower than that of their competitors, even those initially retailing at lower prices.

How to load the autoclave / steam sterilizer correctly?

Get in our video tutorial all important information about the correct loading of the autoclave / sterilizer. The video tutorials for the compilation of an individual loading pattern can be found on our Multimedia channel.

Successful sterilization requires correct cleaning and disinfection of the instruments.

Please always comply with the reprocessing instructions from the instrument manufacturer. When performing instrument care, it is imperative not to use water-repellent care products or water-impermeable oils. Use only those care agents suitable for steam sterilization.

Correct loading of the autoclave is a prerequisite for effective sterilization and best drying results. In this regard, please comply with the following principles while loading the autoclave:

  • Place textiles on the top tray
  • Place the sterilization containers at the bottom
  • Place unwrapped instruments at the bottom
  • Place heavy loads at the bottom
  • Place sterilization packaging (foil and paper pouches) on the top trays. Except when sterilizing in combination with textiles: In this case, place them at the bottom.

As far as possible, sterilization pouches should be placed in an upright position in the steam sterilizer. If you place the sterilization packaging directly on a tray, make sure that the film side faces upwards to prevent the development of water droplets.

The fractionated vacuum used by Class B autoclaves also permits the sterilization of double wrapped instruments e.g. instruments wrapped in two pouches or in a pouch and a sterilization container. Closed sterilization containers (preferably made of aluminium) must be perforated on at least one side to permit steam injection. The MELAstore-Boxes and the MELAG sterilization containers ensure the best-possible sterilization and drying results.

Are bacterial checks (spore tests) prescribed for practice autoclaves?

Routine checks of the steam sterilizers are an important part of hygiene management in a practice and clinic.

Steam sterilizers used to be inspected bi-annually by using biological indicators or after 400 sterilization cycles. This requirement was specified in an obsolete chapter of DIN 58946-6. The current European standard DIN EN ISO 17665-1 does not specify any requirements regarding the use of biological indicators.

Biological indicators such as spore tests are not suitable for assessing the success of sterilization. The sterilization requires a longer holding time than required for the elimination of the biological indicators.

Thus, we recommend the use of a suitable indicator system for checking the batch quality after sterilization: The sterilization outcome of hollow body instruments is subject to control with a helix test body. As a system provider, MELAG developed the helix test bodies MELAcontrol Helix and MELAcontrol Pro to enable performing regular quality checks of the sterilized batches in Class B steam sterilizers. Both test bodies comply with the requirements of EN 867 – 5. Class S autoclaves can be checked with Class 5 indicators.

What is a vacuum test?

With a vacuum test, steam sterilizers monitor how well all steam-carrying parts are sealed. This test is carried out in accordance with DIN 58946-6: 2002 and is thus prescribed by the national hygiene regulations.

If you operate a large autoclave (>1 STU), we recommend carrying out this test on a monthly basis. For a table-top steam sterilizer, the test is recommended to be carried out once a week. Ideally, this will be done on Monday morning before work starts, as a cold sterilization chamber without loading is required.

To start the test, remove the tray mount from the sterilization chamber and check if it is dry. After closing the steam sterilizer, use the control panel to select the vacuum test. Now the air will be evacuated from the chamber of the autoclave. The test starts automatically after pressure equalization has taken place. During the test, the pressure change within the chamber per unit of time is measured to see how much air enters the unit during. If the leak rate exceeds a certain value, the autoclave will issue a malfunction message on the display. If the test is successful, you can start with the instrument decontamination process.

Learn more about routine tests for an autoclave in our video-tutorial.

How to clean the sterilization chamber of an autoclave correctly?

The regular chamber cleaning of your autoclave is an important step of the instrument reprocessing workflow and enables a long-term protection of the device.

For ideal cleaning results and long-lasting shine the MELAG Chamber Protect cleaning set should be applied to the autoclave once a week.

The cleaning set, including the Chamber Protect spray, 50 lint-free cloths and 1 microfibre cloth saves the chamber from discolouration and depsosits and removes even soiling that is invisible to the eye. Approved through extensive material compatibility tests it is particularly gentle on the material of the chamber and door seal and therefor ideally matched to all MELAG steam sterilizers.

Before starting the chamber cleaning, the autoclave should be switched off and cooled down. The Chamber Protect Spray is then sprayed onto the sterilization chamber and the inside of the door and is spread with a lint-free cloth.

After a short exposure time (approx. 3 minutes), the stainless steel surfaces are moistened with demineralized water and then wiped with another cloth that has also been moistened. After a further 5 minutes exposure time, the sterilization chamber and the inside of the autoclave door should be dried with the microfiber cloth.

The cleaning set can be applied to your autoclave as well as to all of your trays.

How to document and approve a sterilization batch?

The process documentation of the autoclave is vital as verification of a successfully completed sterilization program. The documentation can be done manually as well as digitally using a software solution. Learn more about the digital documentation and approval process via the colour-touch Display of the Premium-Class Evolution in our video-tutorial.

Manual documentation and approval takes place with the help of a documentation sheet from our MELAdoc articles. The approval decisions are then recorded by hand. With the help of the MELAdoc label printer, you can further facilitate the documentation process.

After sterilization, batch approval begins with the review and documentation of the correct process. The relevant process parameters are saved in a log file and the success of the batch is displayed on the autoclave’s display. In addition, the sterilization packaging is checked for integrity and dryness, and finally the labeling of the sterilized material takes place. Please always mark the wrapped instruments behind the seal seam on the foil side of the sterilization packaging. After using the instruments, you can remove the label from the foil packaging and transfer it to the patient record.

The approval of the sterilization batch on the documentation sheet requires following information:

  • Personnel-, equipment- and batch number
  • Sterilized on / Usable until
  • Program / Loading
  • Successful sterilization: yes / no
  • Batch indicators (e.g. MELAcontrol Helix) OK: yes / no
  • Release granted: yes / no
  • Signature for release

The log files may be stored on an output medium, such as the MELAflash CF card, for data backup. No additional software is required to open these files. The log files can be simply accessed with a word processing software (e.g. word or text editor). Please note the legal retention periods when storing the approval documents.

MELAtrace meets the requirements for complete documentation and approval quick, secure and paperless. The software solution combines sterilization, cleaning and disinfecting steps to ensure comprehensive and complete documentation of instruments reprocessing. MELAtrace guides you step by step through the approval process. The batches are released via the system and the labels for marking the instruments are printed out via the MELAprint 60. Scanning barcode labels even ensures digital assignment in a patient management software.

How to replace the MELAdem 40 water treatment filter / cartridges?

Learn more in our video tutorial about the correct filter exchange procedure for the MELAdem 40 water treatment system:

Watch now

The MELAdem 40 water treatment unit supplies the steam sterilizer with demineralized water. The Evolution series automatically tests the conductivity of the demineralized water during every sterilization procedure and issues a warning if the water quality is too low. Please change the mixed-bed resin cartridges as soon as the warning is displayed. Before changing the cartridges, please close the tap of the water line. Then start the Universal-Program and abort it after c. 20 seconds. You can now open the cartridge container using the wrench in the housing cap of the MELAdem 40. Please slide the wrench over the cartridge container and turn it clockwise.The water in the cartridge container can be poured into the drain and the exhausted cartridges can be disposed of in the domestic waste. Please insert the new cartridge in the thoroughly rinsed cartridge container and screw the container tight by hand and then with the wrench. Repeat this procedure for the second mixed-bed resin cartridge. After you have re-opened the water tap and have checked the MELAdem 40 for leaks, your steam sterilizer and water treatment unit are ready to use.

What is the difference between our Premium and Pro-Class autoclaves?

Our decades of development experience and focus on the instrument reprocessing segment are the basis for our innovative and permanently reliable products - made in Germany. Learn more about the differences between Premium and Pro-Class autoclaves in the following section:

The advantages of the Premium-Class Evolution

✓ Record operating times: Very fast cycle times of 10 to 25 minutes due to the patented double-jacket technology
✓ Intelligent drying DRYtelligence: Optimum drying results and an 80 % reduction in drying time
✓ Very high loading capacities: For up to eight trays and 9 kg
✓ XXL Colour-Touch Display: Intuitive user interface with integrated software for documentation and approval
✓ Documentation interfaces: CF card slot and two network interfaces in the device at no extra cost
Video Tutorials: how to use the autoclave explained quickly and easily with video tutorials
✓ MELAconnect App: Access the autoclave status and program progress at any time via mobile app
Customized to your decontamination room: As a stand-alone solution or autoclave with fixed water connection in chamber sizes 18 and 24 litres

Discover the product highlights in our video of the Premium-Class Evolution.

The advantages of the Pro-Class

✓ Short operating times: Fast cycle times from 20 to 50 minutes
✓ High loading capacities: For up to 6 trays and 7 kg
✓ Intuitive operation: With MELAG four key concept
✓ Serial interface: For paperless documentation with MELAflash or MELAnet Box
✓ Customized to your decontamination room: As a stand-alone solution or autoclave with fixed water connection in boiler sizes 17, 23 and 29 litres
✓ Vacuklav 24 BL+: With 60 cm chamber depth for sterilization of extra-long instruments such as endoscopes

Discover the product highlights in our Pro-Class video.

What is the advantage of a Class B autoclave?

Hygiene measures to prevent infections are more important than ever in times of COVID-19. In medical practices and clinics, special attention must be paid to the reprocessing of instruments in addition to the new distance and hygiene rules. Because only through sterilization a complete inactivation of all reproductive pathogens and thus absolute safety for patients and team can be achieved.

Numerous questions arise when choosing an autoclave. With regard to reliability, effectiveness and a wide range of applications, there can only be one answer for a practice: sterilization with saturated steam at 134 degrees Celsius. Steam sterilization enables reprocessing of unwrapped and wrapped instruments quickly using a reproducible process. The integrated process documentation provides legally compliant proof of error-free reprocessing.

Air inhibits sterilization and must be removed from the chamber and the hollow bodies of the instruments in advance. DIN EN ISO 13060 differentiates autoclaves into classes B, S and N according to their evacuation performance. Depending on the type and complexity of the instruments, a decision is made as to which sterilization method is suitable.

The fractionated vacuum process of a Class B autoclave reduces the air in the sterilization chamber by repeatedly evacuating the air and introducing steam. This process guarantees optimal saturated steam conditions for sterilization not only of solid and porous instruments, but also of complex hollow body instruments such as handpieces and endoscopes.

Watch the video to learn more about the sterilization process in a class B autoclave.

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