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HTM 02-01 (2026) & Dental Gas Scavenging
The new HTM 02-01 dental gas-scavenging section (§12.37–12.50) — what it says, published 19 August 2026, and how it is met in a real dental surgery.
The 2026 documentation reference
HTM 02-01: Medical Gas Pipeline Systems
Health Technical Memorandum 02-01 is the UK guidance covering the design, installation, validation and verification of medical gas pipeline systems. It sets the compliance benchmark for how medical gases — including the nitrous oxide and oxygen used in inhalation sedation — are delivered safely.
NHS England published the new 2026 edition on 19 August 2026. Its Part A now carries a dedicated dental gas-scavenging section — §12.37–12.50 — which applies to any dental surgery that uses inhalation sedation. This page is about that section: what it says, and how it is met in a real dental surgery.
The standard's §12.40 says the system works by “extracting exhaled gases from around the nasal mask”. That describes the classic double-mask design — the Porter Brown scavenges around the mask and through a flapper valve at the back of the inner mask. The newer Silhouette is different: it extracts from inside the mask and is not a double-mask system. Those two mechanisms are exactly why the breathing-system-specific rates in Part 2 matter.
Reference at a glance
- Document
- HTM 02-01 — Medical gas pipeline systems
- Part
- Part A: Design, installation, validation and verification
- Publisher
- NHS England — 2026 edition, published 19 August 2026
- Status
- Current 2026 edition
- Dental scope
- Part A, §12.37–12.50 — the dental gas-scavenging section
- Key dental figure
- Fan flow no less than 80 L/min (§12.43)
Part 1
What the new edition requires for dental gas scavenging
The dental section of the 2026 HTM 02-01, Part A §12.37–12.50, quoted in full:
DAGS should be used in dental surgeries that use sedation. This section does not apply to general anaesthesia for dentistry performed in operating theatres.
DAGS is a specialised independent system that is a single-chair installation.
Dental scavenging should be connected from the pump unit to the nasal mask disposal tubes using a disposal hose.
This system works by extracting exhaled gases from around the nasal mask.
DAGS should be installed in each dental treatment room. They should be simplex systems.
The unit should comply with BS EN ISO 80601-2-13.
The fan unit should produce a flow rate of no less than 80 L/min and should be controlled by a flow switch.
The unit should have a flow switch and a flow indicator to show that the system is running at a specific flow rate.
There should be an on/off switch on the front of the unit with a green LED indicator to show the unit is powered.
The connection for the disposal hose should comprise a female 30 mm conical connector.
The exhaust should be routed externally using a pipe of at least 32 mm diameter, made of material compliant with fire regulations. This pipe should be sleeved with a copper pipe one size larger.
A risk assessment should be undertaken when determining the discharge location. It should be sited at roof level, at least 5 m away from mechanical inlets and 3 m from passive inlets.
The discharge should not be located over opening windows or doors, or where recirculation of discharged air could occur over parapets.
Warning signs should be placed at the exhaust point.
Quoted from NHS England, HTM 02-01: Medical gas pipeline systems, Part A (2026 edition), §12.37–12.50. The §12.46 30 mm disposable-hose requirement is also addressed in Part 2.
Part 2
The established approach
The section's headline specs describe one particular kind of standalone unit. Here is how those figures land against the way dental scavenging actually works — and what the majority of practices use.
80 L/min is adjustable — the real challenge is the Silhouette
Chairside suction can operate at up to 80 L/min, and the benefit is that it adjusts down easily — on the handpiece and on the vacuum block — so the combined scavenging rate can be maintained across the range. The matching challenge is the newer Silhouette breathing system, which needs only 25–30 L/min at the nasal mask: depending on the strength of the motor, it can be hard to reduce a fixed standalone unit down to 25 L/min.
The dental section reads as written around one niche standalone unit
The §12.43 figure closely matches a fixed standalone 80 L/min anaesthetic gas scavenging unit (such as the Purair 80), which is not what the majority of dental practices use. Its inlet and exhaust connections are much larger than a MiniScav or chairside suction (30 mm), and it requires an adapting hose (30 mm) to connect — whereas a MiniScav or chairside suction uses a standardised connection that suits mainstream dental breathing systems directly. None of the currently established dental breathing systems can be connected to a 30 mm hose or inlet.
Roof-level discharge is situational, not routine
Roof-level extraction is only required where the exhaust would discharge onto a public footpath. Normally, 2 m clearance from any public area or walkway gives sufficient dispersion of waste nitrous oxide. Routing pipework up to the roof is, for a typical dental surgery, unnecessary cost.
AGSS systems are suitable for nitrous-oxide extraction
The new HTM's own note (Part A, §12.14) says AGSS are “not designed for the extraction of self-administered analgesic gases such as oxygen/nitrous oxide mixture”. In dental practice that caveat does not apply: the titrated gases are not self-administered by the patient but are administered and controlled by the clinician. The “self-administered” wording appears to be aimed at patient-controlled analgesia such as Entonox in maternity, where the patient self-administers. Anaesthetic gas scavenging systems have been used for a significant number of years to extract waste N₂O in dental surgeries, in addition to chair suction ports.
Less invasive by design
A MiniScav needs only a 15 mm external wall vent, versus a roughly 35 mm hole for a large standalone unit. A smaller hole means less disruption to the fabric of the surgery, a simpler installation, and quieter operation.
The 30 mm disposable hose is GA pipework — it is not compatible with dental
The section expects a disposal hose with a 30 mm conical connection (§12.39, §12.46). Dental breathing systems already come with their own reusable vacuum hose, so an additional 30 mm disposable hose is unnecessary and impractical. More importantly, a 30 mm disposable hose cannot be connected to current dental breathing systems at all: this is general-anaesthesia (GA) standard pipework being applied to a dental setting.
Correct scavenging rates
The scavenger removes the patient's exhaled waste gas — it should not pull on the gas the patient is inhaling. Rates are matched to the breathing system and the patient:
The modern generation of dental breathing systems are mostly double-mask types. In these, the patient inhales the fresh titrated gases from the inner liner. As they exhale, the waste gases are pushed through a flapper valve into the outer mask where a constant draw — between 40–45 L/min — removes the waste gases safely from the operatory.
The very latest design of the dental breathing system mask is a single, close-fitting hood. The titrated gases are delivered by means of a nasal cannula prong within the mask, and the scavenging takes place internally through a series of well-designed holes in the base.
| Breathing system / case | Scavenging rate |
|---|---|
| Porter Brown / ClearView | 35–45 L/min |
| Silhouette | 25–30 L/min |
Each reference, answered for dental
The section, clause by clause
For every clause of the new HTM dental section: what it requires, and how it is met in a dental surgery.
What it requires
DAGS should be used in dental surgeries that use sedation (not general anaesthesia in operating theatres).
The established approach
A correct statement — this page is about dental-sedation scavenging, and the section correctly applies here rather than to theatre anaesthesia.
What it requires
A specialised, independent, single-chair installation.
The established approach
Correct in principle: scavenging is typically per chair, per room. Typically, a MiniScav or chairside suction port is the proportionate single-chair answer unless a suitably placed AGSS terminal is available which can be connected by means of a special AGSS probe adaptor.
What it requires
Connected from the pump unit to the nasal-mask disposal tubes using a disposal hose.
The established approach
This is incorrect for dental. Dental breathing systems already include their own reusable vacuum hose. Detailing a separate 30 mm disposable hose which cannot be connected to any of the current dental breathing systems is meaningless.
What it requires
Works by extracting exhaled gases from around the nasal mask.
The established approach
This is incorrect for dental. All current dental breathing systems and masks are designed to extract exhaled waste gases from within the mask system; for example, the classic double-mask design (Porter Brown). The exhaled gases are drawn through a flapper valve at the back of the inner mask into the outer mask and then drawn away through the vacuum tubing. The latest type, Silhouette, extracts from inside the mask and is not a double-mask system.
What it requires
Installed in each dental treatment room; simplex systems.
The established approach
Agreed — one dedicated unit per room, simplex, is the right model, unless the facility has the option of using a suitably placed AGSS terminal or chair suction port. (Established practice within dental for 20+ years)
What it requires
The unit should comply with BS EN ISO 80601-2-13.
The established approach
This is the ISO standard written specifically for anaesthetic-workstation (AGSS) equipment electrical safety. However, of note, it is also the same class the new HTM’s §12.14 says is not suited to N₂O extraction. However, what must be taken into account is the existing extensive and widespread use of MiniScav units in dental operatories. Specifically designed for dental application and compliant with BS EN ISO 80601-2-13.
What it requires
Fan flow of no less than 80 L/min, controlled by a flow switch.
The established approach
80 L/min is not itself a problem — chairside suction and AGSS terminals can run up to 80 L/min (and in excess of) and these allow adjustment using the vacuum block, so the scavenging rate is maintained. The challenge is potentially the new Silhouette breathing system, which needs only 25–30 L/min at the nasal mask: depending on motor strength, it can be potentially problematic to reduce a fixed standalone unit down to 25 L/min. In this case, preferred use would be connection to a MiniScav.
What it requires
A flow switch and flow indicator showing the system running at a specific rate.
The established approach
Potentially good practice, but the operator will have to use the vacuum gauge that comes with the breathing system itself. A generic gauge on the pump can be misleading: it reads the pump’s own output, not the actual vacuum rate the breathing system was designed for. The operator should set and confirm the breathing system’s own integral vacuum gauge throughout the procedure.
What it requires
Front on/off switch with a green LED power indicator.
The established approach
Correct — a clear powered/on indicator is required.
What it requires
Disposal-hose connection is a female 30 mm conical connector.
The established approach
This is incorrect for dental. 30 mm conical is GA-standard pipework. Dental breathing systems use their own reusable hose, much smaller bore and thick-walled or reinforced. MiniScav/chairside suction connect with a standardised fitting that suits mainstream dental systems. A 30 mm disposal hose is neither required nor connectable to any of the current dental systems. This echoes the use of passive dental breathing systems (large 22 mm or 30 mm hose) — these have been obsolete for approximately 18 years.
What it requires
Exhaust routed externally, at least 32 mm diameter, fire-regulation compliant, sleeved with a larger copper pipe.
The established approach
This is incorrect for dental. This is theatre-scale exhaust. A MiniScav discharges through a 15 mm external wall vent — far less invasive, simpler and quieter — while assisting with staff COSHH exposure levels.
What it requires
Risk assessment; discharge sited at roof level, at least 5 m from mechanical inlets and 3 m from passive inlets.
The established approach
This is incorrect for dental. Roof-level discharge is only required where the exhaust would discharge onto a public footpath. Normally 2 m clearance from any public area or walkway gives enough dispersion of waste N₂O from a standard inhalation sedation session. Routing to the roof is unnecessary cost for a typical dental surgery and often impractical in dental settings.
What it requires
Discharge not located over opening windows or doors; avoid recirculation over parapets.
The established approach
Sensible — never discharge over openings. A practical low-level wall vent follows the same no-recirculation principle, nitrous oxide being heavier than air and sinks naturally, but dispersed by natural air movements.
What it requires
Warning signs placed at the exhaust point.
The established approach
Agreed — the discharge point should be clearly signed; if this is deemed applicable. Signage often brings attention to the outlet with undesired consequences in certain geographical areas.
The discipline of proper use
Six habits that keep a surgery compliant
Whatever the documentation debate, these six habits keep a surgery safe, quiet and compliant.
Use a dedicated sedation flowmeter
A purpose-designed, dedicated sedation flowmeter, regularly maintained by an OEM-trained service engineer. It delivers the titrated oxygen / nitrous oxide mix and, on modern units, prevents a hypoxic mixture being delivered.
Make active scavenging the first line of protection
Connect the breathing circuit and mask to a sustained active draw at the correct rate for your breathing system throughout the whole procedure, without fluctuation.
Keep a range of mask sizes
Nasal mask fit is the difference between a good seal and waste-gas leakage.
Assess surgery ventilation
Understand whether the room has natural or mechanical ventilation and enhance it where needed.
Monitor staff exposure — at least annually
(COSHH occupational limit: 100 ppm over an 8-hour TWA), repeating sooner if readings are high or unusual.
Run a pre-use check every session
A quick pre-use check of the flowmeter, breathing system and scavenger is designed to identify any potential faults.
From the manual — Medical Gases: Use, Care and Maintenance
Good practice, in practice
This is the working detail behind the six habits — condensed from the “Medical Gases: Use, Care and Maintenance” chapter of the BDJ Clinician's Guide (Pickles, R A Medical Services Ltd, 2026). Four operational areas do most of the heavy lifting:
Gas supply: guard the pressure and the hoses
- Only 137 bar (oxygen) and 44 bar (nitrous oxide) cylinders are designed for inhalation sedation flowmeters. The newer 230 or 300 bar cylinders are not suitable — using one can cause serious malfunction or damage to the equipment.
- Pressure-reducing regulators and low-pressure hoses carry a 5-year replacement cycle, sooner if any wear or damage is seen. Regulators can develop instability with age and sometimes fail without warning.
- Hoses are colour-coded and non-interchangeable — white for oxygen, blue for nitrous oxide — with DISS fittings that make a wrong connection physically difficult.
Storage & handling: keep it simple, keep it safe
- Store cylinders in a secure, weatherproof, well-ventilated area, clearly identified with compressed-gas warning and no-smoking signs — and inform the emergency services of the store location.
- Secure cylinders so they cannot topple (rigid brackets or hook-and-chain) and keep them separated into full, empty and faulty.
- Keep oil, grease and lubricants away — only oxygen-service lubricants — and handle oxygen with clean, oil-free hands (or gloves).
- Use Full and In-use cylinder labels — a requirement of the NHS England clinical standards for dental anxiety management.
The four-cylinder stand: care for the daily driver
- Bodok seals make the gas-tight connection at the yoke. A lost or flattened seal leaks (often with an audible hiss) — inspect them regularly, keep spares, and let the OEM engineer change them during the annual service.
- Modern stands (Matrx, Accutron) carry cylinder restraints that stop the E-size cylinders swinging and protect the pin-index yoke — older stands lack them.
- If yoke pins are ever damaged or missing, take the stand out of use until an OEM service engineer has repaired it.
- Valves differ by supplier: BOC cylinders open with a ratchet key, Air Liquide with an integral valve — train staff in the system you actually run.
Going piped? Use the proportionate standard
- Degreased medical-grade copper to BS EN 13348, silver-based brazing with no flux on any oxygen or nitrous oxide joint, completed by a competent medical-gas installer.
- Colour-code and label pipework to BS EN ISO 7396-1 (oxygen black-on-white, nitrous oxide white-on-blue), including flow-direction labels along the run.
- Purge with nitrogen after installation, then run a purging test and a functional test once cylinders and outlets are fitted — and record the results.
- Terminate at self-sealing gas-specific outlets (GEM 10); carry out an annual visual inspection and leak checks, and replace regulators and hoses every 5 years.
Whoever touches the gas must be trained for it
Every member of staff involved in handling, changing or connecting cylinders should be trained for the system in use and familiar with it — including spotting the signs of a failing regulator, a damaged hose or a leaking seal. Non-return valves prevent backflow of gases between supply and equipment.
Condensed from J. Pickles, Navigating the World of Dental Inhalation Sedation (BDJ Clinician's Guides, 2026), Ch. 2 — Medical Gases: Use, Care and Maintenance.
The equipment behind proper use
What we supply, and how it is used
Every piece of equipment R A Medical supplies is chosen to make the active, proportionate approach practical — and every flowmeter and scavenger we supply is backed by our own UK engineering and servicing.
Not sure what your surgery actually needs?
Our team will help you specify the established, compliant setup for your room — and keep it that way with annual OEM servicing.
References: Health Technical Memorandum 02-01: Medical gas pipeline systems, Part A — Design, installation, validation and verification (NHS England, 2026 edition, published 19 August 2026), §12.37–12.50 (dental gas scavenging) and its note to §12.14; the chapter “Medical Gases: Use, Care and Maintenance” in the BDJ Clinician's Guide to Inhalation Sedation (Pickles, R A Medical Services Ltd, 2026); Purair 80 AGSS product documentation (MEC Medical). This page is educational guidance, not a substitute for the current official documents or for your own risk assessment.