Hot-air sterilizers vs. steam sterilizers
Hot-air or steam sterilizer?
Why only saturated steam meets the standard for critical instruments — and what the RKI has to say about it.
Germany Austria Switzerland
Quick answer
For critical medical devices, the RKI recommends steam sterilization with saturated steam (autoclave). Hot air does not reliably meet the KRINKO requirements for critical instruments.
Hot air vs. steam: the difference
- Hot-air sterilizers use hot air to sterilize objects. They operate at higher temperatures than steam sterilizers.
They can be effective for sterilization, but some microorganisms may survive at the lower temperatures.
Hot-air sterilizers are frequently used in laboratories for glassware and metal instruments. - Steam sterilizers use steam to sterilize objects. They operate at lower temperatures, which can be gentler on certain materials.
As a rule they are more effective, because steam enables better heat transfer and thereby ensures more thorough sterilization.
Steam sterilizers are widely used in medical facilities, particularly for instruments and equipment that are heat-sensitive.
In medical practice, the admissibility of hot-air sterilization for critical items has been viewed negatively since 2021. Although this method is recognized for non-critical and semi-critical instruments when the devices have mechanical air movement, it does not meet all the requirements for the sterilization of 'critical' medical devices.
The German Medical Devices Operator Ordinance (MPBetreibV) refers in § 4 para. 2 to compliance with the recommendations of the Robert Koch Institute (RKI) on hygiene in the reprocessing of medical devices. According to point 2.2.4, the RKI prefers thermal sterilization procedures with saturated steam (at 121 °C or 134 °C) due to their more reliable effectiveness. A procedure using saturated steam is only possible with autoclaves.
The use of hot-air sterilization is not explicitly prohibited; however, the legally binding KRINKO requirements cannot be met for critical instruments. A risk assessment in accordance with the RKI recommendation is required for medical practices, and for the reprocessing of 'critical' medical devices the RKI recommends the use of steam sterilizers (autoclaves).
The MPBetreibVO (§ 4.2) requires medical devices to be reprocessed using suitable validated procedures and taking the manufacturer's instructions into account. The exact definition of a 'validated procedure' is not unambiguous, but some experts interpret it as automatic documentation of the sterilization processes, while others understand it as a reproducible and error-resistant procedure.
Responsibility for reprocessing lies with the operator of the sterilizer, who must carry out a practice-specific risk assessment in order to choose the appropriate procedure for sterilization. With Class B steam sterilizers from Steri24 the requirements for all risk levels are met.
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Frequently Asked Questions
Hot air sterilizers vs. steam sterilizers – key questions answered clearly.
What is the difference between a hot-air sterilizer and a steam sterilizer?
A hot-air sterilizer works with dry, hot air at comparatively high temperatures, whereas a steam sterilizer (autoclave) uses saturated water vapor under pressure. Steam transfers the heat considerably more efficiently and evenly, thereby achieving more reliable sterilization.
Why is a steam sterilizer better than a hot-air sterilizer?
For critical instruments, hot-air sterilizers have no longer been permitted since 2021 under the legally binding KRINKO recommendation; steam autoclaves are required. In addition, packaged items cannot be reliably sterilized in a hot-air sterilizer.
Does the RKI recommend hot air or steam for critical medical devices?
For critical medical devices, the RKI recommends thermal sterilization with saturated steam (autoclave). Hot air does not reliably meet the KRINKO requirements for critical instruments.
What does sterilization with saturated steam mean?
Saturated steam is saturated water vapor that releases its heat at a defined pressure and temperature (typically 121 °C or 134 °C). This heat transfer reliably kills all microorganisms, including spores, and is only possible with an autoclave.
Is hot-air sterilization still permitted since 2021?
Hot-air sterilization is not expressly prohibited, but since 2021 it cannot meet the legally binding KRINKO requirements for critical instruments. For non-critical and semi-critical instruments it may be recognized under certain conditions.
Can a hot-air sterilizer be validated?
No, hot-air sterilizers generally cannot be validated. Furthermore, they do not meet the RKI recommendations for the reprocessing of critical instruments (blood contact).
Is an ultrasonic cleaner, UV or hot-air device enough, or do I need an autoclave?
As soon as instruments come into contact with blood or mucous membranes (critical instruments), a Class B autoclave is mandatory; ultrasonic, UV and hot-air devices are not sufficient for this. The ultrasonic cleaner complements the autoclave during pre-cleaning, but does not replace it.
Why does steam transfer heat better than hot air?
When saturated steam condenses on the instruments, a large amount of energy is suddenly released, heating the items quickly and evenly. Dry air transfers heat much more slowly, which is why hot air requires longer times and higher temperatures and yet remains less reliable.
At what temperature does a steam sterilizer operate?
Steam sterilizers typically operate at 121 °C or 134 °C. At 134 °C the standard program usually runs considerably faster, while 121 °C is gentler on more sensitive materials.
Why do some germs survive in a hot-air sterilizer?
Hot air heats the items more slowly and unevenly, so not all areas reliably reach the required temperature for the required time. As a result, individual microorganisms can survive, which makes successful sterilization uncertain.
Can I sterilize packaged instruments in a hot-air sterilizer?
No, packaged items cannot be reliably sterilized in a hot-air sterilizer. For packaged, hollow and porous instruments, a Class B steam sterilizer with a fractionated vacuum process is required.
What are critical, semi-critical and non-critical medical devices?
Non-critical products only touch intact skin, semi-critical ones come into contact with mucous membranes, and critical ones penetrate skin or mucous membranes or come into contact with blood. The higher the risk, the stricter the requirements for reprocessing; critical instruments require steam sterilization.
Which sterilization do I need when instruments come into contact with blood?
As soon as instruments come into contact with blood or mucous membranes, they are considered critical and must be reprocessed with a Class B steam sterilizer (autoclave). Hot air is not suitable for this.
What is the difference between Class A, B and N autoclaves?
Class B offers full-scale sterilization with a vacuum process for packaged, unpackaged, hollow and porous instruments. Class N may only sterilize unpackaged, solid instruments and is not permitted in human medicine; Class A is not a European standard. For medical practices you need a Class B device.
What does Class B mean for an autoclave?
Class B refers to full-scale steam sterilizers with a fractionated vacuum process that can also sterilize packaged, hollow and porous instruments. For instrument reprocessing in medical facilities, a Class B device is mandatory in Germany.
What is the benefit of the vacuum process in a Class B autoclave?
The fractionated vacuum process removes the air from the chamber, packaging and cavities, so that the saturated steam reaches all surfaces. Hot-air devices do not have this air removal, which is why they fail with packaged and hollow items.
Which RKI recommendation does the MPBetreibV refer to?
The German Medical Devices Operator Ordinance (MPBetreibV) refers in § 4 para. 2 to compliance with the RKI recommendations on hygiene in the reprocessing of medical devices. For critical instruments, these recommend thermal sterilization procedures with saturated steam.
What is a validated procedure in reprocessing?
The MPBetreibV requires reprocessing with suitable validated procedures. This means a reproducible, error-resistant and demonstrably effective procedure; a steam sterilization process can be validated, a hot-air process cannot.
Who is responsible for choosing the sterilization procedure?
Responsibility lies with the operator of the sterilizer. They must carry out a practice-specific risk assessment and select the appropriate procedure; for critical instruments this leads to steam sterilization.
Do I need a risk assessment for my practice?
Yes, a risk assessment in accordance with the RKI recommendation is required for medical practices. It classifies the instruments by risk level and determines the appropriate reprocessing and sterilization procedure from this.
Do I meet all risk levels with a Steri24 Class B autoclave?
Yes, with a Class B steam sterilizer from Steri24 you meet the requirements for all risk levels – including critical instruments. This puts you on legally secure footing.
What are hot-air sterilizers typically still used for?
Hot-air sterilizers are frequently used in laboratories for glassware and metal instruments, for example when no packaged or critical items are being reprocessed. For the medical reprocessing of critical products they are not suitable.
Is a steam sterilizer gentler on instruments?
Steam sterilizers operate at lower temperatures than hot-air devices, which can be gentler on heat-sensitive materials. At the same time, they sterilize more thoroughly thanks to the better heat transfer.
Can I switch from a hot-air device to an autoclave?
Yes, the switch is straightforward. A Class B steam sterilizer fully replaces the hot-air device and additionally meets the requirements for critical instruments. The best way to determine which size fits your needs is via our autoclave configurator.
Are sterilization pouches also suitable for hot-air / dry-heat sterilizers?
No, our self-sealing pouches are designed exclusively for steam sterilization in autoclaves, not for hot-air or dry-heat sterilizers. There is no suitable sterilization packaging for those devices.
What is an autoclave and who needs one?
An autoclave is a steam sterilizer for reprocessing medical instruments for reuse. It is needed wherever critical instruments that come into contact with blood or mucous membranes are used, for example at dentists, podiatrists, in foot care or in tattoo studios.
What exactly does sterilization mean?
Sterilization refers to the killing or inactivation of all microorganisms, including bacteria, viruses, fungi and their resistant spores. An autoclave achieves this with saturated water vapor under pressure.
Why is disinfection not enough and is sterilization necessary?
Disinfection reduces germs but does not necessarily kill all microorganisms and spores. For critical instruments, complete sterilization is mandatory, which is reliably achieved only with saturated steam in the autoclave.
Is a thermal disinfector (washer-disinfector) enough, or do I also need an autoclave?
A thermal disinfector cleans and disinfects the instruments, but does not replace sterilization. For critical instruments, steam sterilization in the Class B autoclave is mandatory after reprocessing in the washer-disinfector.
How does instrument reprocessing with steam sterilization work?
Reprocessing is carried out in several steps: pre-cleaning/cleaning (e.g. ultrasonic bath or thermal disinfector), disinfection, drying and packaging, and then steam sterilization in the autoclave. The exact requirements follow the RKI/KRINKO and the manufacturer's instructions.
Which materials may I reprocess in the steam sterilizer?
In the Class B steam sterilizer, steam-stable metal and plastic instruments as well as packaged, hollow and porous items can be reprocessed. The decisive factor is the instrument manufacturer's specifications regarding steam sterilizability.
Do the Steri24 steam sterilizers meet the applicable standards?
Yes, our Class B steam sterilizers are Class B medical devices and designed in accordance with EN 13060, with CE marking via TÜV SÜD. They thus meet the normative requirements for the sterilization of critical instruments.
What happens if I continue to reprocess critical instruments with hot air?
When reprocessing critical instruments with hot air, the legally binding KRINKO requirements cannot be met, and successful sterilization is not assured. For legally secure and safe reprocessing, a Class B steam sterilizer is required.
Which sizes of steam sterilizers does Steri24 offer?
We offer Class B steam sterilizers in sizes 3L, 12L, 18L, 23L and 45L. The easiest way to determine which size fits your instrument volume is via our autoclave configurator or in a consultation.
Which steam sterilizer is right for my practice?
That depends on the instrument volume, the instrument length and the medical field. Small applications often manage with the 3L, while practices usually choose 12L to 23L. Use our autoclave configurator for a suitable recommendation.
How long does a sterilization cycle in the steam sterilizer take?
The duration depends on the program, load and device size. Quick programs of small devices run very rapidly, while programs for packaged items with drying take longer. Compared to hot air, steam cycles are generally considerably shorter.
Do I need distilled water for the steam sterilizer?
Yes, steam sterilizers require treated water (e.g. distilled or demineralized) to avoid the build-up of limescale and residue. For this we offer suitable water treatment such as AQUAdem or a water distiller.
What is a vacuum test and why is it important for a Class B device?
The vacuum test checks the tightness of the chamber and ensures that the vacuum process reliably removes the air. It is a regular routine check on the Class B autoclave – a procedure that hot-air devices do not have.
How do I document the sterilization in a legally secure way?
Our Class B autoclaves offer integrated digital logging and a printer; with SteriTrace, paperless RKI documentation is also possible. This way every batch can be traceably documented.
Is validation of the steam sterilizer mandatory?
In Germany, validation is mandatory for everyone who reprocesses critical medical instruments used on humans; the basis is, among others, the MPBetreibV. Hot-air devices cannot be validated and are ruled out for critical instruments.
What does the validation of an autoclave mean?
Validation is a formal examination that demonstrates that your autoclave and the entire reprocessing process meet the applicable standards and sterilize reliably. It is usually carried out on site every 2 years using your instruments as the load.
Does Steri24 handle commissioning, validation and maintenance of the steam sterilizer?
Yes, commissioning, initial validation, instruction and maintenance can be booked and are carried out on site – with free travel in Germany, Austria and Switzerland. You can find details and prices in the shop or in a non-binding offer.
Does the autoclave have to be validated in the veterinary sector?
In the purely veterinary sector, validation is not legally required, as the obligation only applies to the reprocessing of instruments used on humans. Voluntary validation is of course possible.
Is a steam sterilizer also mandatory for foot care or podiatry?
As soon as critical instruments that come into contact with blood are reprocessed in foot care or podiatry, a Class B steam sterilizer is mandatory. A hot-air or UV device is not sufficient for this.
Are steam sterilizers equally mandatory in Austria and Switzerland?
In Austria and Switzerland too, strict hygiene requirements apply to critical instruments, which in practice require steam sterilization; in some cases additional national requirements apply (e.g. ÖNorm). We advise you on a country-specific basis and are on site throughout the entire DACH region.
How much does a compact Class B steam sterilizer cost?
The current promotional price depends on the model and is shown on the product page. Compact devices are cheaper than large practice devices; you will receive a specific recommendation including price via the configurator or a consultation.
Is it worth switching from an aging premium device?
Yes. If you replace an older, expensive device, with a Class B steam sterilizer from Steri24 you get equivalent performance, a dense on-site service network and a fairer price – directly from the manufacturer without depot markup.
What sets Steri24 apart from other providers in terms of service?
Steri24 combines fair prices with a large, fast on-site service network in the DACH region, including a 24h emergency hotline. This way you get premium performance and service quality at a price that established expensive manufacturers usually do not offer in this form.
What should I do if the vacuum test fails?
A failed vacuum test usually indicates that air is flowing into the chamber and that the contact pressure of the door seal needs to be increased or the seal replaced. You will find a quick guide on the inside of the door; if that does not help, please use the help form at steri24.de/help.
How do I find the right steam sterilizer for my needs?
The fastest way is via our autoclave configurator: you enter your medical field, instrument volume and requirements and receive a suitable recommendation. Alternatively, we will advise you personally and prepare a non-binding offer.