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October 9, 2026
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The autoclave is one of the most critical equipment in highly regulated laboratories, hospitals and industries. It is a team that uses high pressure and temperature water vapor to sterilize materials, instruments and biological waste. Its objective is to eliminate microorganisms, including spores, guaranteeing safe processes in these sectors.
What you need to know about the autoclave in laboratories:
A Laboratory autoclave It is a thick-walled metallic container with an airtight closure designed to work at high pressures and temperatures. It is a robust physical containment system where a controlled tight atmosphere is generated to subject the materials to cycles of lethal humid heat for microscopic life.
Its main function is the total elimination of all forms of microbial life in objects and substances. This encompasses irreversible inactivation and destruction of viruses, vegetative bacteria, fungi, and spores more resistant to temperature.
The physical principle is based on the transfer of thermal energy by saturated steam at high pressure. Water in a liquid state is heated in a sealed chamber until it is transformed into water vapor. As the internal pressure rises above the atmospheric pressure, the boiling point of the water rises proportionally, reaching design temperatures of up to 134 °C. This vapor penetrates microorganisms, causing the immediate denaturation and coagulation of its structural proteins and vital enzymes, which results in its biological death.
To avoid costly maintenance errors and hazards within the enclosure, it is critical to differentiate which materials are autoclaved:
Dynamic operation of a typical autoclave cycle is divided into sequential phases controlled by the computer’s computer system:
The water contained in the internal boiler or supplied by an external steam generator is heated by electrical resistance. The steam begins to accumulate in the sterilization chamber, gradually raising the global temperature of the enclosure.
It is a critical phase to ensure the effectiveness of the process. The presence of bubbles or bags of cold air acts as a thermal insulator that prevents moist steam from entering direct physical contact with the surfaces of the samples. Modern autoclaves bleed the air through gravity methods (steam, lighter, displaces cold air down) or actively through fractionated pre-vacuum cycles using powerful mechanical vacuum pumps.
Once the target temperature is reached evenly throughout the chamber, the sterilization timer starts. The most widespread time and temperature standard parameters at the laboratory and industry level are:
Once the plateau time is over, the chamber releases the remaining vapor pressure in a controlled manner. In equipment equipped with a vacuum pump, an active drying phase is executed to extract excess moisture from the instrument and textile bags. Finally, the camera cools gradually until the sensors indicate that it is safe to open the door of the equipment.
For a cycle to be considered microbiologically effective, the equipment control sensors must constantly verify three thermodynamic variables: temperature, pressure and time. If a single of these variables deviates from the tolerance range, the cycle is classified as non-conforming and the process must be aborted and repeated.
The autoclave morphology, capacity and performance vary according to the workflow needs and the sample volume of the center:
Compact equipment of reduced dimensions (between 15 and 50 liters of capacity) designed to be installed on laboratory countertops. They are the standard solution for lower volume clinics, teaching laboratories or dental and veterinary clinics.
Top loading sterilizers and tower format. They are highly demanded in general microbiological laboratories to process large flasks with liquid culture media, bottles and bottles of reagents, thanks to the fact that they make the most of the cylindrical volume of the chamber.
Front loading equipment with cylindrical or rectangular cameras. They offer improved ergonomics for the placement of instrument trays and wire baskets, and are recommended for integration in clinical and diagnostic analysis laboratories.
Modular systems where the door opens pivoting or automatic vertical slider. They allow to expedite manual loading and transport carts, facilitating continuous work in research centers.
Large industrial equipment (from 150 to more than 2,000 liters) integrated in a built-in dividing technical walls. They are common in biotechnological production areas, pharmaceutical pilot plants and hospital sterilization plants.
The European standard UNE-EN 13060 classifies small steam sterilizers according to the type of loads that can be safely processed:
The manufacture, use and validation of wet heat sterilizers is part of an international strict regulatory body:
ISO 17665 (Sterilization of Wet Heat Sanitary Products) is the global reference standard. Exclusively establishes the technical requirements for the development, technical validation, routine control and documentation of steam sterilization processes in autoclaves.
It regulates the design specifications and the physical-chemical test methods applicable to industrial autoclaves and large steam sterilizers used in the hospital and pharmaceutical environment.
It is the European reference standard for small steam sterilizers (with chamber volume less than 60 liters). Classify the equipment in class B, S and N and detail the thermal validation tests that each category must support.
In the pharmaceutical sector, the GMP Guidelines (especially Annex 1 of the GMP Europeans on the manufacture of sterile drugs) require that each cycle of autoclave used in production be rigorously validated documentary to demonstrate its reproducibility and integrity of data.
Both the ISO 17665 and the US FDA guidelines (21 CFR Part 11) require autoclaves to keep a printed or digital record of each cycle performed. This record must indissolubly include the date, time, cycle number, operator identification and readings from analog pressure and temperature sensors.
Technical validation is the only scientific and instrumental procedure capable of ensuring that an autoclave cycle effectively sterilizes the load placed inside.
What does it mean to validate an autoclave?
Validating an autoclave is a documented process that provides objective evidence that the equipment, operating under certain parameters and types of load, achieves the lethal microbiological reduction conditions at all points of the sterilization chamber in a reproducible way.
The standard validation methodology is structured in three consecutive phases:
For these tests, high-precision data loggers are used with flexible PT100 resistance probes or calibrated traceable thermocouples. These thermal sensors are introduced through a dedicated validation port in the autoclave to measure the actual temperature at multiple internal geometric points of the camera.
It consists of mapping the camera to find the coldest point (slow heating point) of the installation. The steam must maintain the uniformity of the temperature (typically between +0°C and +3°C over the sterilization range) throughout the cavity.
Physical temperature sensors are introduced directly inside the vials, clothing bags, test tubes and reagent bottles to record how long it takes to effectively penetrate the heat into the geometric core of the load, calculating the cumulative biological lethality value of the cycle.
The ISO regulations 17665 and the GMP guidelines state that the technical validation of an autoclave is not a one-time action. The installation must be subject to periodic annual technical revalidations (or after major repairs to joints, generators or motherboards) to certify that its operating conditions remain unchanged over time.
For daily monitoring of cycles, technical staff is supported by a complementary system of three types of physical, chemical and microbiological indicators:
The life and accuracy of an autoclave depends on the methodical execution of a predictive and corrective maintenance plan:
The inner chamber, support trays, and water outlet drain filter should be cleaned daily to avoid dirt build-ups, remnants of culture media, or lime that can plug the evacuation ducts.
Door silicone gaskets suffer from high thermal and instrumental wear due to pressure variations, so they must be visually inspected every week and lubricated or replaced periodically to prevent microbial or steam leaks.
Internal temperature probes (PT100) and pressure transducers must be calibrated annually against ENAC accredited metrological calibration patterns to avoid drifts in reading critical variables.
Preventive changes should be scheduled in high operational fatigue parts such as heating resistors, overpressure safety valves, inlet air check filters to the chamber and mechanical seals of the vacuum pumps.
All mechanical work, inspections and repairs carried out on the autoclave must be placed in a record book of equipment auditable by quality inspectors or health agencies.
On LABSOM We provide a differential value of technical engineering and applied metrology to ensure that your sterilization equipment meets the most demanding international and national regulations. Our team of specialized engineers attends your center comprehensively through the following high-tech services:
The correct operation and methodical technical validation of an autoclave constitute the fundamental pillar to guarantee biosecurity, analytical validity and Compliance with laboratory standards o Plant that produces clean environments. Entrusting the instrumental validation of your autoclaves to a specialized team such as Labsom ensures that your processes strictly comply with the most advanced international standards, optimizing the operational performance of your biomedical installation.
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A standard autoclave usually reaches 121°C (at a pressure of 1.1 bar) or 134°C (at 2.1 bar), depending on the thermal resistance of the material to be sterilized.
Disinfection reduces the load of pathogens to safe levels but does not eliminate the most resistant bacterial spores. Sterilization is an absolute process that destroys all viable microbial life, including spores.
According to ISO 17665, an autoclave must undergo complete instrumental validation annually or immediately after major repairs on its critical components.
Installation qualification tests (IQ), empty operation (OQ) and performance with real load (PQ) are executed by thermal mappings with independent physical probes to calculate the actual lethality value.
Thermosensitive plastics (such as low-density polystyrene or polyethylene), flammable volatile solvents, corrosive acids, or chemical reagents that degrade with heat should not be introduced.
Class B autoclaves remove air by pre-vacuum fractionated by pump, allowing for sterilizing porous, hollow or bagged loads. Class N passively displaces the air by gravity and only serves for solid instruments without bagging.
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