If you’ve started shopping for an autoclave, you’ve almost certainly run into the alphabet soup: Class N, Class S, Class B. The internet will happily tell you Class B is the answer to everything. That’s nearly right but not always right, and the wrong answer for your setting can cost you anywhere from a few hundred pounds (overspent) to a Local Authority compliance notice (underspent).
This is a setting-by-setting honest answer, written by people who service the kit. We do sell more Class B than anything else, because most clinics actually need one. But there are a couple of genuine cases where an N or an S is the right call, and a couple of myths that need clearing up.
BS EN 13060 is the standard governing small steam sterilisers under 60 litres. It defines three classes. The difference between them is what they do with the air inside the chamber.
Class N: Naked. Gravity displacement. No vacuum stage. Will validly process solid, unwrapped, non-porous, non-hollow instruments and nothing else. Cycle times are shorter, usually 15 to 20 minutes for a 134 °C unwrapped cycle, and the units are cheaper, typically £600 to £1,500 new in the UK.
Class S: Specified. A middle ground. The manufacturer specifies exactly what loads the unit is validated for and you can only put those loads through. Some Class S units include a single-pulse vacuum which means they handle some wrapped loads, but only the wrapped loads on the manufacturer’s list.
Class B: Big or Broad, depending who you ask. Pre-vacuum and post-vacuum drying. Validated for everything: wrapped instruments, porous loads, hollow instruments, lumens, hinges, the lot. Cycle times of 25 to 50 minutes depending on the programme. New units start around £2,500 entry level and climb past £8,000 for the premium tier with cloud traceability and water recycling.
That’s the textbook answer. Now the useful answer, by setting.
In a UK dental practice, you can argue HTM 01-05 doesn’t literally write “you must buy a Class B autoclave.” It writes something more practical: that wrapped instruments can be stored for up to 12 months, pre-sterilisation wrapped if Type B or S, post-sterilisation wrapped if Type N, whereas unwrapped instruments are limited to a single working day in the clinical area (paragraph 2.4k and §4.22). It also requires that hollow instruments such as handpieces and 3-in-1 tips have their internal channels properly sterilised. The only autoclave class that can handle wrapped storage AND hollow instruments together is Class B.
That’s the why behind the “B-type is the dental standard” line everyone repeats. It’s not a clause in HTM 01-05 saying so; it’s the consequence of what HTM 01-05 actually requires.
There’s a fuller dental write-up in our no-nonsense buyer’s guide for dental practices if you want the longer answer. The summary: if you pouch anything for storage, if you process handpieces, or if you do any kind of surgical or implant work, the only defensible choice is Class B.
We’ve written a longer piece on this, the podiatry autoclave UK buyer’s guide, because the answer for podiatry needs unpacking. The short version: most podiatrists pouch box-joint nail nippers for storage sterility and sterilise hinged or hollow instruments. None of that is a Class N job. Class B is the practical answer.
The exception: a podiatrist who has gone fully single-use across every reusable instrument, has nothing pouched, and is sterilising nothing. That clinic doesn’t actually need any autoclave. Almost nobody operates that way.
This is the setting where people get the answer most wrong, and it’s the one where being wrong is most expensive.
Tattoo studios and body-piercing premises in England are licensed by the Local Authority under the Local Government (Miscellaneous Provisions) Act 1982. Wales now has its own regime under Part 4 of the Public Health (Wales) Act 2017, in force since 29 November 2024, the underlying compliance expectations around sterilisation are similar. Compliance is governed by your council’s bylaws, and the bylaws most LAs have adopted are based on the Kent Code of Practice for Hygienic Skin Piercing. That code is explicit:
“For the sterilisation of wrapped or pouched items and instruments with hollow parts (i.e. tubes, grips and tips), a vacuum steam autoclave MUST be used.”
And, on why:
“Wrapped or hollow items will not allow steam penetration unless there is active removal of air (vacuum stage) from within these items.”
If you operate a piercing or tattoo business and you process pouched items, tubes, grips or tips, your LA will expect a vacuum autoclave, which in practice means Class B or a properly load-validated Class S that explicitly covers your kit.
The “we don’t pouch anything” defence is half-true at best. It holds for a piercer running only solid, externally-threaded jewellery and clamps, using single-use cartridges for the gun, and storing nothing. That genuinely is a Class N use case. The moment you pouch one item for storage, run any tube or grip through, or your LA inspector reads “vacuum required” in their copy of the Kent Code, the N is the wrong machine.
Ring your council’s Environmental Health team before you buy if you’re not sure. Bylaws vary subtly.
Beauty clinics carrying out electrolysis or other skin-puncturing treatments fall under the same LA-licensing regime as tattoo and piercing. Most electrolysis needles are single-use sterile, so the autoclave only needs to handle reusable tweezers, forceps and probes, all solid metal, no hinges, no lumens.
A Class N can do that job, provided nothing is pouched and everything goes from autoclave to use within the same session. A Class S widens the envelope to give you wrapped storage if the manufacturer’s load list includes your specific instruments. A Class B handles whatever, and most established clinics buy a Class B anyway because the workflow flexibility is worth the extra spend.
The honest answer for a small electrolysis-only setup: if cash flow is tight and you genuinely never pouch anything, a Class N or S is defensible. Most clinics that start there end up upgrading within two or three years because workflow changes. Worth thinking about now.
Veterinary practices accredited under the RCVS Practice Standards Scheme are expected to operate vacuum autoclaves, and the convention is Class B because surgical kits get wrapped. Even outside the formal scheme, anything more than basic consultative practice means surgical hinges, lumens and wrapped trays, which is, again, a Class B requirement by load type if not by clause.
If you’re a vet-only practice considering a Class N because the surgical work is rare, the realistic question is whether you can guarantee no wrapped or hollow load will ever go through the machine. Most vet practices can’t, and the answer becomes Class B.
The one we hear most often: “I don’t need a B-type because I don’t sterilise anything fancy.”
It’s nearly always wrong, and here’s why. The class question isn’t about how fancy your instruments are. It’s about whether air can be removed from the load during sterilisation. A simple pair of forceps in a pouch is more challenging for an autoclave than the same forceps unwrapped, because the pouch traps air. A nail nipper with a box joint is harder than a straight scalpel handle, because the joint traps air. The class you need is dictated by your load, not the cost of your kit.
If you put any wrapped, hinged, or hollow item through your autoclave, you need vacuum. That’s a Class B, or in narrow cases a Class S explicitly validated for that load.
Class S autoclaves are sometimes pitched as the smart middle ground between N and B. The honest answer is they’re defensible only if you do the homework: get the manufacturer’s load list, confirm every reusable instrument you own is on it, and accept that adding a new instrument type later might mean it isn’t validated to sterilise the new one. The class only validates the loads the maker has tested, nothing else.
For small, low-complexity clinics with a stable kit list, a Class S can be the right call. For most dental practices and any clinic with growth ambitions, the safer answer is just a Class B and don’t think about it again.
Indicative new prices in the UK, ex VAT, vary by chamber size and feature set:
We sell three Class B brands across that range, the Castellini C Series at the value end, the Stern Weber SW Series as a no-frills entry, and the Mocom B Classic where design matters. We also have refurbished units in stock for buyers on a tight budget, give us a call on 01274 265566 and we’ll tell you what’s currently available.
If you’d rather have a five-minute conversation than read another comparison article, give us a ring on 01274 265566 or use the contact form. We’ll ask about your setting, your caseload, and your workflow, and we’ll tell you what we’d put in our own clinic, including when “go Class N and save the money” is genuinely the right answer.
