---
title: "Autoclave guide: steam sterilizers and dental sterilization equipment"
url: https://www.kelingmed.com/blog/autoclave-guide/
published: 2026-09-23
updated: 2026-10-19
author: Keling Medical export team
---

# Autoclave guide: steam sterilizers and dental sterilization equipment

How to choose dental sterilization equipment and hospital steam sterilizers: Class B vs N vs S, gravity vs vacuum cycles, sizing, utilities and validation.

## Key points

- Dental sterilization equipment should be a Class B steam sterilizer to EN 13060 when the clinic reprocesses handpieces, lumened instruments or wrapped and porous loads.
- Steam sterilization works by saturated steam contact at a set temperature for a set holding time, typically 121°C or 134°C, after air has been removed from the chamber and load.
- Small sterilizers up to 60 L fall under EN 13060; large hospital sterilizers that hold at least one 300 × 300 × 600 mm sterilization unit fall under EN 285.
- Size a hospital autoclave from the peak daily instrument volume, cycle time and number of shifts, then add a second unit so sterilization never depends on one machine.
- Every medical autoclave needs installation, operational and performance qualification plus routine monitoring with physical, chemical and biological indicators.


The right dental sterilization equipment for most clinics is a Class B steam sterilizer, a benchtop autoclave with vacuum air removal that can sterilize wrapped, porous and hollow instruments such as handpieces. Hospitals use the same steam sterilization principle in larger chamber sizes. This guide explains sterilizer classes, cycles, sizing, utilities and validation, so you can specify the right machine.

## How steam sterilization works

Steam sterilization kills microorganisms, including bacterial spores, by bringing saturated steam into contact with every surface of the load at a set temperature for a set holding time. When steam condenses on a cooler instrument it releases a large amount of heat at once, which denatures microbial proteins far faster than dry hot air does.

Three conditions must all be met:

- **Air removal.** Air pockets block steam. A pack with trapped air can stay unsterile even when the chamber gauge reads correctly.
- **Saturated steam at temperature.** The common combinations are 121°C (250°F) at about 0.1 MPa (15 psi) gauge and 134°C (273°F) at about 0.21 MPa (30 psi) gauge.
- **Holding time.** Typical minimum exposure is about 3 minutes at 134°C in a vacuum cycle, and 15–30 minutes at 121°C depending on the load and air removal method. Your sterilizer's validated cycle, not a generic figure, is what counts.

The process is described by ISO 17665 (moist heat sterilization of health care products) and, in US health care facilities, by ANSI/AAMI ST79. For a wider comparison with dry heat, ethylene oxide and radiation, see our guide to [sterilization vs disinfection and the main sterilization methods](https://www.kelingmed.com/blog/sterilization-vs-disinfection/).

## Gravity displacement vs dynamic air removal

The way a steam sterilizer removes air is the biggest technical difference between machines, and it decides which loads it can handle.

A **gravity displacement sterilizer** lets incoming steam, which is lighter than air, push air down and out through a drain at the bottom of the chamber. It is simple, has few parts to fail and suits liquids, unwrapped solid instruments and laboratory waste. It is slow and unreliable for dense textile packs and lumens.

A **dynamic air removal sterilizer** (often called prevacuum or pre-vac) uses a vacuum pump or a series of steam pressure pulses to pull air out before the exposure phase. It sterilizes porous packs, wrapped trays and hollow instruments in shorter cycles and also gives a better post-cycle vacuum drying phase.

| Feature | Gravity displacement | Dynamic air removal (prevacuum) |
|---|---|---|
| Air removal | Steam pushes air out by gravity | Vacuum pump or steam pulses |
| Suitable loads | Liquids, unwrapped solids, lab waste | Wrapped trays, textiles, lumens, handpieces |
| Typical cycle at 134°C | Longer, less common | About 3–4 min hold plus pre-vacuum and drying |
| Drying | Limited | Vacuum drying |
| Daily air removal test | Not applicable | Bowie-Dick type test |
| Typical buyers | Labs, small clinics, field hospitals | Hospitals, CSSDs, dental clinics |

## Class B, N and S sterilizers (EN 13060)

EN 13060 covers small steam sterilizers with a chamber volume up to 60 L and groups their cycles into three types. When you buy a dental sterilizer or a small medical autoclave, the class tells you what the cycles have been tested for.

- **Class B ("big small sterilizer")**: tested for all load types, including hollow (lumened), porous and wrapped loads. It always uses fractionated vacuum air removal.
- **Class N ("naked")**: only for solid, unwrapped instruments. No vacuum. Items are used soon after the cycle, because they are not packaged.
- **Class S ("specified")**: the manufacturer declares which load types the cycle handles, for example single-wrapped solid instruments or a specific hollow load. Read the claims carefully.

A class B sterilizer is the safe default for dentistry, ophthalmology, day surgery and any clinic that stores wrapped instruments. A Class N unit only makes sense for simple, unwrapped solid instruments used immediately.

## Choosing an autoclave for a dental clinic

An autoclave for a dental clinic must handle handpieces, ultrasonic scaler tips, burs, mirrors, probes and cassettes, and most of these are wrapped or have narrow internal channels. That is why dental sterilization machines are usually Class B benchtop units with 17–23 L chambers.

Points to check before you buy a dental sterilizer:

1. **Cycle claims** for hollow and wrapped loads, and the time of a full 134°C cycle including drying.
2. **Chamber size and tray count.** Measure your instrument cassettes against the internal tray dimensions.
3. **Water supply.** Most benchtop units use a reservoir filled with distilled, demineralized or reverse-osmosis water; poor water leaves deposits and stains.
4. **Data recording.** A printer, USB or network log makes cycle records easy to keep.
5. **Test programs** for a Bowie-Dick type test, a hollow-load test and a vacuum leak test.

Dental tool sterilization also depends on the steps before the autoclave: cleaning, ultrasonic or washer-disinfector processing, drying, inspection and packaging in pouches or wrapped cassettes. Peel pack sterilization in pouches made to ISO 11607 works well for single instruments; label each pouch with date, sterilizer and cycle number.

## Benchtop, vertical or horizontal: matching size to workload

Steam sterilizer machines range from 18 L benchtop units to horizontal chambers of several hundred liters. The right size depends on peak daily instrument volume, not the average.

| Type | Typical chamber | Typical users | Keling examples |
|---|---|---|---|
| Portable / benchtop | 18–24 L | Dental, clinics, outpatient, small labs | [KL-ST001 Portable Pressure Steam Sterilizer](https://www.kelingmed.com/products/laboratory-sterilization/kl-st001-portable-pressure-steam-sterilizer/) (18 L and 23 L, 134°C, 0.22 MPa); [KL-ST003 Portable Pressure Steam Sterilizer](https://www.kelingmed.com/products/laboratory-sterilization/kl-st003-portable-pressure-steam-sterilizer/) (18 L and 24 L cylindrical) |
| Vertical (top-loading) | 35–100 L | Laboratories, small hospitals, media and waste | [KL-ST002 Vertical Pressure Steam Sterilizer](https://www.kelingmed.com/products/laboratory-sterilization/kl-st002-vertical-pressure-steam-sterilizer/) (35–100 L, up to 138°C) |
| Horizontal (front-loading) | 150–400 L | Hospital sterilizers, CSSD, large labs | [KL-ST004 Horizontal Pressure Steam Sterilizer](https://www.kelingmed.com/products/laboratory-sterilization/kl-st004-horizontal-pressure-steam-sterilizer/) (150–400 L, 0.25 MPa); [KL-ST005 Horizontal Steam Sterilizer](https://www.kelingmed.com/products/laboratory-sterilization/kl-st005-horizontal-steam-sterilizer/) (150–360 L, 115–138°C) |

A simple sizing method for hospital sterilization equipment:

- Count the instrument trays, packs and containers processed on your busiest day.
- Divide by how many fit in one load, then by the number of cycles one machine can run per shift (cycle time plus loading, unloading and cooling).
- Add capacity for growth and for the daily test cycle.
- Plan **at least two sterilizers** in any department where surgery depends on them, so maintenance or a failed test does not stop the operating room.

Large sterilizers that hold at least one sterilization unit (300 × 300 × 600 mm, about 12 × 12 × 24 in) are covered by EN 285. Ask which standard the machine is designed and tested to, and request the test reports.

## Utilities and installation

An electric steam sterilizer with its own steam generator is the easiest to install, and it is the norm for benchtop and vertical units. Large horizontal sterilizers may use building steam or an integrated generator. Before ordering, confirm:

- **Power**: single-phase for most benchtop units (the 18 L and 23 L Keling benchtop model in the table above is rated at 2.2 kW), three-phase for large chambers.
- **Water**: treated feed water to the quality the manufacturer specifies, and cooling water if the vacuum pump needs it.
- **Drainage** that tolerates hot condensate, and adequate ventilation for heat and steam release.
- **Floor loading and access** for a large chamber, including door swing and service clearance behind the machine.
- **Pass-through layout** for CSSDs: a double-door sterilizer with the loading side in the clean packing area and the unloading side in sterile storage.

Our [sterile processing department guide](https://www.kelingmed.com/blog/sterile-processing-department-guide/) explains how the sterilizer fits into the full reprocessing workflow.

## Validation, monitoring and maintenance

A medical autoclave is only as good as its validation. ISO 17665 describes qualification of sterilizing equipment in three stages:

- **Installation qualification (IQ)**: the sterilizer is installed and connected as specified.
- **Operational qualification (OQ)**: it delivers the specified cycles within tolerance, empty and with test loads.
- **Performance qualification (PQ)**: it sterilizes your actual load configurations, documented with temperature sensors placed in the load.

After that, routine monitoring uses physical records (time, temperature and pressure for every cycle), chemical indicators in and on every pack, a daily Bowie-Dick type test for prevacuum machines and biological indicators at a regular interval. Our [sterilization indicators guide](https://www.kelingmed.com/blog/sterilization-indicators-guide/) explains each test.

Maintenance items to plan for include door gasket replacement, chamber and drain strainer cleaning, valve and safety-valve checks, temperature and pressure sensor calibration, and pressure vessel inspection as required by local regulations. Clean the sterilizer chamber with the method in the instructions for use, never with abrasive pads or chlorine products that damage stainless steel.

## Immediate use steam sterilization

Immediate use steam sterilization (IUSS) is an unwrapped or minimally contained cycle for an item needed urgently, such as an instrument dropped during a procedure. The item still has to be cleaned properly first and is carried to the point of use without storage. IUSS is not a fix for short instrument inventories and should not be used for implants except in a documented emergency. If a department relies on IUSS every day, the solution is more instrument sets or more sterilizer capacity.

## What to put in a sterilizer specification

A clear tender or request for quotation saves weeks of back-and-forth with sterilizer manufacturers. Include:

1. Chamber volume, internal dimensions and number of trays or sterilization units.
2. Load types: solid, hollow, porous, wrapped, liquids, waste.
3. Required cycles (for example 121°C and 134°C, Bowie-Dick test, leak test, liquids, drying).
4. Air removal method and class (EN 13060 Class B, or EN 285 for large units).
5. Single or double door, loading orientation and installation space.
6. Steam source, power supply, water quality and drainage.
7. Cycle documentation: printer, data export, user access levels.
8. Accessories such as perforated stainless steel sterilization trays ([KL-TC076 Stainless Steel Sterilization Tray](https://www.kelingmed.com/products/medical-trolleys/kl-tc076-sterilization-tray/)), loading carts and baskets.
9. Documents: declaration of conformity, quality system certificate, pressure vessel documentation, test reports, IFU and service manual.
10. Training, spare parts list and warranty.

Keling Medical has manufactured hospital equipment since 1996 and works under an ISO 13485:2016 quality system certified by SGS. Ask for the documents that apply to the specific model and destination country.

## Next steps

Choose the sterilizer class from your load types, size it from your busiest day, and budget for validation and routine monitoring from the start. Browse Keling's [laboratory and sterilization equipment](https://www.kelingmed.com/products/laboratory-sterilization/), then [send your requirements through the quote form](https://www.kelingmed.com/contact/#rfq) with load types, daily volume and utilities, and the export team will suggest a configuration.


## FAQ

### What sterilizer does a dental clinic need?

Most dental clinics need a Class B benchtop steam sterilizer, because handpieces and other instruments with narrow channels need vacuum air removal to be sterilized reliably. A 17–23 L chamber covers a typical two- to four-chair practice. Busy clinics often add a second unit so one cycle can run while the other cools or is tested.

### What is the difference between Class B, N and S sterilizers?

Under EN 13060, Class B cycles are tested for solid, hollow and porous loads, wrapped or unwrapped. Class N cycles are only for solid, unwrapped items. Class S cycles cover the specific load types the manufacturer declares, which may include some hollow or wrapped items. Check the cycle claims in the instructions for use.

### What temperature does a medical autoclave reach?

Most medical autoclaves run at 121°C (250°F) or 134°C (273°F). The 134°C cycle at about 0.21 MPa gauge pressure is faster and is the common choice for wrapped instruments in vacuum sterilizers. Lower settings such as 115°C or 121°C are used for heat-sensitive liquids and some laboratory media.

### How does a steam sterilizer work?

A steam sterilizer removes air from the chamber, fills it with saturated steam under pressure, holds the load at the sterilizing temperature for a validated time, then exhausts the steam and dries the load. The condensing steam releases heat directly onto every surface it reaches, which denatures microbial proteins quickly.

### What is immediate use steam sterilization?

Immediate use steam sterilization (IUSS) is a short cycle for an item needed urgently, such as a dropped instrument during surgery, which is used directly without storage. It is meant for exceptional cases only, not as a substitute for adequate instrument inventory, and implants should not be processed this way except in a documented emergency.

### What is a gravity displacement sterilizer?

A gravity displacement sterilizer lets incoming steam push air down and out through a drain at the bottom of the chamber. It is simple and robust but removes air poorly from wrapped packs and lumens, so cycles are longer. Dynamic air removal (prevacuum) sterilizers use a pump or steam pulses and handle porous and hollow loads.

### How often should an autoclave be tested?

Physical readings are checked every cycle and a chemical indicator goes in every pack. Prevacuum sterilizers run a Bowie-Dick type test each day before the first load. Biological indicators are run at least weekly, and in every load that contains an implant. Follow your national guidance and the sterilizer's instructions.