Hospital isolation room design: pressure, air and layout

By ZY Cleanroom · Updated 2026-11-01 · Sources at the end of the page

Three room types

Values are design parameters from the documents named. Check the current edition and local code.

Layout and doors

In the HTM lobby design, supply air enters the lobby and passes through a pressure stabiliser into the room. It leaves through a door undercut or transfer grille to the en-suite extract.

CDC calls for self-closing doors in these rooms. Seal windows in positive rooms. Keep exhaust outlets more than 25 ft (7.6 m) from air intakes, the AIA figure cited in CDC's Table 2.

Worked example: airflow and offset

Example only, with assumed numbers. A room 4.5 m by 4 m and 2.7 m high has a volume of 48.6 m³. Twelve air changes is 583 m³/h, or 0.16 m³/s. Ten is 486 m³/h.

To stay negative, extract must exceed supply by the air that leaks in. HTM 03-01 Appendix 4 gives 0.03 m³/s through a closed single door at 5 Pa, assuming 3 to 4 mm gaps. That is 108 m³/h, about 2.2 air changes of offset in this room. Real gaps differ, so confirm by test.

Doors, comfort and noise

HTM 03-01 Table 4 gives isolation rooms 20 to 25 °C, up to 60% RH and 35 dB(A). Its Appendix 4 notes that factory-assembled steel-frame door sets with pre-hung leaves have effectively no closed-door leakage. For those doors, design airflow follows the air-change rate or open-door protection, whichever is greater.

Exhaust and filters

CDC describes protective environment rooms as built for patients such as allogeneic hematopoietic stem cell transplant recipients, with HEPA filtration, high air change rates and minimal leakage. CDC says air from a negative room is preferably exhausted outside. Where recirculation is unavoidable, the air must pass through a HEPA filter, rated at least 99.97% at 0.3 µm.

A positive room needs the supply filtered to at least that grade in CDC's table. HTM 03-01 lists EPA10 to EPA12 filters for protective rooms. Match the filter to the patient group.

Monitoring

CDC prefers a calibrated hand-held reading daily for engineering purposes, and allows smoke or flutter checks of direction. Fit a room monitor with an alarm, and write the failure mode into the brief: what the room does when a fan stops.

Put these in the room data sheet

State the room type, the pressure value and sign, the air path from supply to extract, the air change basis, the filter grade, the door type and closer, the monitor and alarm, and what the room does when a fan stops. Each line can then be tested at handover.

Who approves the room

Your health regulator or accreditation body judges the hospital, not the contractor. The contractor builds to your room data sheet and supplies test results. To have a room list reviewed, send it to ZY Cleanroom, a cleanroom design-and-build contractor with its own panel factory in Tianjin, China.

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• Modular operating theatres: scope, air and pressure standards
• Turnkey cleanroom contractor
• Room list builder

Sources

• CDC, Guidelines for Environmental Infection Control in Health-Care Facilities (2003), section C, Air (web page dated 21 December 2023; checked 31 October 2026)
• CDC, Guidelines for Environmental Infection Control in Health-Care Facilities (2003), B. Key Terms Used in this Guideline (checked 31 October 2026)
• NHS England, Health Technical Memorandum 03-01, Specialised ventilation for healthcare premises, Part A (published 22 June 2021; checked 31 October 2026)