Class N and Class S Autoclaves: What They Can and Cannot Sterilise
N and S are the two EN 13060 classes below Class B. They cost less and often run faster — and they are proven for a narrower set of loads. Here is where the line falls.
N, S and B side by side
EN 13060, the European standard for small steam sterilisers of up to 60 litres, does not grade machines from good to bad. It classifies cycles by the loads they have been proven to sterilise. A machine is described by the cycles it offers, which is why some Class B units also carry N or S cycles.
| Question | Class N | Class S | Class B |
|---|---|---|---|
| Loads proven | Unwrapped solid instruments only | Unwrapped solid instruments plus the load types the maker names | Wrapped and unwrapped solid, porous and hollow loads |
| How air is removed | Passively — steam pushes the air out | Varies by model: pressure pulses or a vacuum stage | Repeated vacuum pulses (fractionated pre-vacuum) |
| Pouched instruments for storage | No | Only if wrapped loads are on the maker’s list | Yes |
| Handpieces, cannulae and other lumens | No | Only if that hollow load type is listed | Yes |
| Gauze, drapes and gowns | No | Only if porous loads are listed | Yes |
| Built-in air-removal tests | No | Some models | Yes — Bowie-Dick or helix, and a vacuum leak test |
Read next Class B autoclaves in depth
What Class N is good for — and where it stops
N is often remembered as “naked”: the load goes in unwrapped and comes out for immediate use. Without a vacuum stage, steam has to push the air out of the chamber by itself. That works on smooth, open metal surfaces. It does not reliably work inside a pouch, a fold of fabric or a narrow tube, where air stays trapped and steam cannot reach the surface.
- Suited: solid, unwrapped metal instruments — forceps, scissors, nippers, tweezers — used straight after the cycle.
- Not suited: anything you pouch or wrap to store, because the inside of the pack cannot be shown to be sterile.
- Not suited: hollow instruments such as dental handpieces, cannulae, suction tips or anything with a lumen.
- Not suited: porous loads such as gauze, drapes and gowns.
- Once the door opens, unwrapped instruments are exposed to the room. They stay sterile only until they are handled or set down, so use them at once.
- Cycles are usually shorter, with no vacuum stage before the hold — but drying is simpler too, so check how dry a full load comes out.
Read next Class N for beauty and tattoo studios
Class S: read the load list, not the letter
Class S means “as specified by the manufacturer”. The maker must name the load types each S cycle has been proven on — for example unwrapped solids plus single-wrapped instruments, or certain hollow items — and the cycle is proven only for those. Two Class S machines can therefore cover very different loads.
Ask for the list in writing
The instructions for use should state the load types for each S cycle. If you are told a Class S unit “can do pouches”, ask to see where the manufacturer says so.
Check the hollow-load wording
EN 13060 separates narrow-lumen items, such as dental handpieces, from simple hollow items with wider openings. A cycle proven for one is not automatically proven for the other.
N and S cycles on a Class B machine
Some Class B units also offer N or S cycles as shorter options. Euronda’s E10 brochure, for example, lists N and S cycles that can be unlocked alongside its five B cycles where national rules allow. A fast N cycle on a B machine is still an N cycle: use it only for loads N is proven for.
Read next Euronda autoclave buyer’s guide
Choosing between N, S and B
Choose from the most demanding load you will process, not the most common one. One pouched or hollow item a week decides the class.
| Your situation | Usually enough | Why |
|---|---|---|
| Unwrapped solid tools, used straight after the cycle | Class N | Matches what N is proven for |
| Mostly solid tools, some single-wrapped, no lumens | Class S — if wrapped loads are listed | Depends entirely on the maker’s load list |
| Instruments pouched and stored for later | Class B | Only B is proven for all wrapped loads |
| Dental handpieces, cannulae, suction tips | Class B | Narrow lumens need fractionated vacuum |
| Gauze, drapes, gowns or textile packs | Class B | Porous loads trap air |
| Not sure what you will process in two years | Class B | Covers every load type; N may limit you later |
Read next Class B or N for a GP clinicWhy dental clinics need Class B
Monitoring a Class N or S autoclave
- Record every cycle — printout, memory or a written log of time, temperature and pressure.
- Put a chemical indicator in every load; for unwrapped instruments, place it on the tray among them.
- Bowie-Dick and helix tests are designed for vacuum cycles. A Class N unit without a vacuum stage does not run them; a Class S unit with one may — follow the manufacturer.
- Run biological (spore) tests at the interval your infection-control policy sets, and after any repair.
- Give it the same cleaning, water and door-seal care as any autoclave: dirty water and a worn seal fail N cycles just as they fail B cycles.
Read next Autoclave tests explainedAutoclave cleaning schedule
Related guides
Autoclave supply near you
Delivery, installation and training across Malaysia from Batu Caves, Kota Kinabalu and Kuching.
Frequently asked questions
What does Class N mean on an autoclave?
Can a Class N autoclave sterilise instruments in pouches?
Is Class S as good as Class B?
Is a Class N autoclave enough for a tattoo or nail studio?
Get a written quotation
Tell us your clinic or lab type, daily workload and location. We match suitable models and send a written quotation with delivery, installation and training spelled out.