The decontamination room is the bit of a new build you cannot bolt on later. The drains go in before the floor, the sinks before the splashbacks, the ventilation before the ceiling. Every retrofit we get called to looks the same: a too-small room with the autoclave six inches from the dirty sink because someone scaled the plan off a Pinterest board.
This is the HTM 01-05 Chapter 5 walkthrough we’d put in front of any dentist at architect-drawings stage. What the standard literally requires, what it leaves to your judgement, and what the engineering bodies recommend on top.
Paragraph 5.5 is the key passage for any new build:
“When setting up new premises or planning significant modification to existing premises, the separation of the decontamination area from the clinical area is recommended. The provision of two separate rooms is the preferred option as it provides for a higher degree of separation between dirty instruments awaiting decontamination and cleaned/sterilized instruments… one room for dirty activity (cleaning and preliminary inspection of instruments); and one room for clean activity (inspection, sterilization and wrapping instruments).”
Two-room separation is the explicit Best Practice answer for a new build. One-room operation with internal dirty-to-clean workflow is the floor (Essential Quality Requirements). In-treatment-room decontamination is technically still permitted under EQR but the standard makes clear (§5.1) that “as dental practices progress towards higher standards, removing the decontamination process from the treatment room should be a priority.”
For a squat practice on an architect’s blank sheet, you have no excuse not to design for Best Practice. The marginal build cost of a second small clean room is far less than the retrofit cost five years later when CQC tightens its line.
HTM 01-05 §5.7 sets out the design points for a single decontamination area. Read it as a walking tour:
“The dirty zone will be used to receive contaminated instruments. An area of benching should be clearly designated for this purpose and used for no other activity.”
“The washer-disinfector (where available) and/or washing and rinsing sinks or separate bowls within a single sink unit should be installed adjacent to the receiving area… The ultrasonic cleaner (where used) should be separated from the receiving area and adjacent to the rinsing sink/bowl.”
“After washing and disinfection (where applicable), the instruments and devices require inspection. A dedicated clean area of benching with good task lighting should be provided.”
“The sterilizer should be situated well away from the other activities/facilities in order to promote staff safety and good decontamination practice.”
The flow on the plan should read left to right or right to left without doubling back: receive → wash → rinse → ultrasonic (or WD) → inspect → sterilise → wrap → store. If you find yourself drawing an arrow that crosses itself, your layout is wrong.
For the two-room Best Practice option, the dirty room gets receive/wash/rinse/ultrasonic; a double-ended washer-disinfector or pass-through hatch carries instruments into the clean room; the clean room gets inspect/sterilise/wrap/store. §5.7 specifically allows the WD to be built directly into the dividing wall.
The common shorthand of “HTM 01-05 requires three separate sinks” is a simplification. The literal text permits two bowls in a single double-sink unit (one for washing, one for rinsing) plus a distinctly separate wash-hand basin. That’s two physical sinks under EQR, three under Best Practice.
The wash-hand basin spec at §6.10 is precise:
“The basin should not have a plug or an overflow and be fitted with a remote running trap (that is, the U-bend is not directly under the plughole). It should have a sensor-operated or lever-operated mixer tap. Taps should not discharge directly into the drain aperture as this might generate aerosols.”
Note the sensor-OR-lever wording. Sensor taps are not mandatory; elbow-lever satisfies. If your budget pushes you towards lever-operated, you’re still compliant.
The decontamination sinks themselves need to be deep enough to fully submerge the longest instrument you process, typically 250mm depth or more, with hot and cold mixer supply plumbed into mains drainage.
§6.46 covers worktops:
“All work surfaces where clinical care or decontamination is carried out should be impervious and easily cleanable. They should be jointless as far as is reasonable; where they are jointed, such joints should be welded or sealed.”
§6.47 covers floors:
“Flooring in clinical care and decontamination areas should be impervious and easily cleanable. Carpets, even if washable, should not be used. Any joins should be welded or sealed. Flooring should be coved to the wall to prevent accumulation of dirt where the floor meets the wall.”
The standard finishes a UK decontamination room is built to:
What inspectors photograph and write up in reports: dirty grout joints behind taps, silicone failures at sink edges, uncoved flooring meeting the wall, painted skirting boards that have absorbed splash.
This is where many design specs go wrong. HTM 01-05 itself does not put a number on ventilation. §6.42 is qualitative:
“The ventilation system in the decontamination area or room(s) should be designed to supply reasonable quantities of fresh air to the positions where persons work and to remove excess heat from equipment and processes.”
§6.43 adds direction:
“Where used, mechanical extract units should be ceiling- or wall-mounted. Care should be taken to ensure that airflow is from clean to dirty.”
The hard quantitative figure comes from elsewhere. IHEEM’s Technical Guidance VPT.GN.001.V01 (March 2021), which applies HTM 03-01 ventilation principles to dental facilities, specifies that instrument cleaning rooms should achieve a minimum of 10 air changes per hour and be maintained at a negative pressure of −10 Pa to surrounding areas. Adjacent clean utility / clean storage areas should run at 6 air changes per hour at +5 Pa positive pressure.
The honest position for an architect spec is: HTM 01-05 sets the principle (clean-to-dirty airflow, no free-standing or ceiling fan-only units), and IHEEM sets the design number to engineer to. Mechanical extract through the dirty end, mechanical supply through the clean end, balanced for the recommended pressure cascade.
A practical equipment-positioning checklist taken from §5.7 with engineering judgement layered on:
Footprint reality: a 17-litre Class B autoclave from the Castellini, Stern Weber or Mocom range needs around 500mm of worktop run with 100mm rear clearance for ventilation. A Tethys H10 Plus washer-disinfector needs 470 × 500mm benchtop plus 100mm rear. Plan the worktop length around these footprints, not the other way round.
HTM 01-05 §2.4(k) sets the storage rules verbatim:
“Wrapped instruments may be stored up to 1 year… Unwrapped instruments in the clinical area: maximum storage 1 day. Instruments should be: dry; and protected from contamination, for example in mini-racks placed in cupboards or in covered drawer inserts. Instruments should not be stored on open work surfaces, particularly in clinical areas. Unwrapped instruments in a non-clinical area: maximum storage 1 week.”
Design the clean-zone storage as sealed wall cupboards or drawers, not open shelves. Open shelving above a worktop is one of the most common findings on first-CQC visits to a new practice.
Lighting at the inspection bench gets “good task lighting” (§5.7) without a lux number. Design to CIBSE LG2 (lighting for healthcare buildings), typically 500 to 1000 lux at the inspection surface. Daylight is a bonus but doesn’t replace the task lamp.
If you’re at architect-drawings stage, ring us on 01274 265566 before the plumbing layout goes in. We review decontamination room plans for new-build dental practices routinely. We can spec the autoclave, the washer-disinfector and the validation package against your worktop length and your throughput, then install and validate everything to HTM 01-05 from day one.
The kit options sit on the practice equipment page and the first-year compliance bundle is on the service and maintenance page.
