Cleanroom temperature and humidity requirements

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

Published ranges

These are design values from the documents named. Check the current edition.

What the standards actually say

Annex 1 para 9.6 asks that temperature and relative humidity be controlled within ranges that suit the product, process and personnel and support the defined cleanliness. Para 4.25 lists temperature and humidity tests in qualification.

EU Part IV for ATMPs asks that lighting, temperature, humidity and ventilation suit the activity and not harm the product or equipment (para 4.11).

For static control, the ESD Association says ANSI/ESD S20.20 does not rely on humidity. Items are typically qualified at 12% ± 3% RH and 23 ± 3 °C. Humidity helps but does not control charge, so grounding still matters.

Dew point and condensation

A surface colder than the air's dew point gets wet. Chilled pipes, cold glazing and uninsulated duct are common cases. The table is calculated with the Murphy and Koop (2005) vapour pressure formula for liquid water.

Worked example: heat sets airflow

Example only, with assumed values. Equipment gives off 5 kW. Supply air is 8 K cooler than the room. Air is 1.2 kg/m³ with a specific heat of 1.006 kJ/(kg·K).

Airflow equals heat divided by density, specific heat and temperature difference: 5 ÷ (1.2 × 1.006 × 8) = 0.52 m³/s, or about 1,860 m³/h. In a 120 m³ room that is 15.5 air changes per hour. Heat alone can set the airflow, so state the heat load in the room data sheet.

Worked example: removing moisture

Example only, calculated at 101,325 Pa. Make-up air at 24 °C and 60% RH holds 11.2 g of water per kg of dry air. Room air at 22 °C and 45% RH holds 7.4 g/kg. The difference is 3.8 g/kg.

Take the 0.52 m³/s above as the make-up flow, which is 0.62 kg/s of air. Removing 3.8 g/kg takes out about 2.4 g/s, or 8.5 kg of water per hour. This is the water only. It excludes the cooling energy.

How to write it down

State the set point, the tolerance, the measuring position, the room state and the alarm limits. Example only: 22 ± 2 °C and 30 to 60% RH at 1.5 m above floor, at rest and in operation, trended.

Give a separate target for the process if it needs one. UK guidance puts these rooms under building management system control.

Who approves the room

Your regulator or customer auditor judges the facility, not the contractor. The contractor builds to your room data sheet and supplies test data. 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.

Related guides

• EU GMP grades A to D compared with ISO classes
• HEPA filter integrity and leak testing
• Cleanroom pressure alarm: how to find the cause
• ISO 5 and ISO 6 cleanroom requirements
• Turnkey cleanroom contractor
• Room list builder

Sources

• NHS England, Health Technical Memorandum 03-01, Specialised ventilation for healthcare premises, Part A (published 22 June 2021; checked 31 October 2026)
• ANSI/ASHRAE/ASHE Addendum y to Standard 170-2025, Ventilation of Health Care Facilities, Table 7-1 (approved 22 September 2026; checked 31 October 2026)
• NABH, Revised Guidelines for Air Conditioning in Operation Theatres (issue 4, November 2018; checked 31 October 2026)
• EudraLex Volume 4, Annex 1: Manufacture of Sterile Medicinal Products (published 25 August 2022; applied from 25 August 2023, and from 25 August 2024 for point 8.123; checked 31 October 2026)
• European Commission, Guidelines on Good Manufacturing Practice specific to Advanced Therapy Medicinal Products, Part IV of EudraLex Volume 4 (adopted 22 November 2017; checked 31 October 2026)
• EOS/ESD Association, Does an ESD control program require humidity controls? (1 August 2024; checked 31 October 2026)
• Murphy and Koop (2005), Review of the vapour pressures of ice and supercooled water for atmospheric applications, Quarterly Journal of the Royal Meteorological Society 131, 1539-1565 (formula used for the calculated dew points; checked 31 October 2026)
• ISO 14644-1:2015, Cleanrooms and associated controlled environments, Part 1: Classification of air cleanliness by particle concentration (published 9 December 2015; checked 31 October 2026)