ISO 7726:2025

Overview - ISO 7726:2025 (Ergonomics of the thermal environment)

ISO 7726:2025 specifies the minimum characteristics and measurement methods for instruments that quantify physical quantities characterizing thermal environments. The third edition modernizes the previous 1998 version by clarifying the distinction between basic (directly measured) and derived (calculated) physical quantities and by formally introducing measurement uncertainty. This standard supports consistent, reliable monitoring of thermal conditions where human comfort, health or strain are central concerns.

Key topics and technical requirements

• Scope and purpose
  • Defines instrument minimum characteristics and acceptable measurement methods for thermal-environment assessment.
• Basic vs derived physical quantities
  • Basic quantities measured directly: air temperature, radiation, plane radiant temperature, dew point, relative humidity, surface temperature, air velocity, globe temperature, psychrometric and natural wet‑bulb temperatures.
  • Derived quantities calculated from basic measurements: mean radiant temperature, radiant temperature asymmetry, operative temperature, water vapour partial pressure, humidity ratio, turbulence intensity, etc.
• Instrument characteristics
  • Requirements for accuracy, response time and suitability for in-situ monitoring; includes integrating and point-measurement device guidance.
• Measurement methods and monitoring
  • Specifications for spatial and temporal sampling, mapping measured data and classifying measurement regimes into type C (moderate environments) and type S (severe environments).
• Measurement uncertainty
  • Formal guidance on evaluating and reporting uncertainty of measurement results.
• Informative annexes
  • Practical measurement guidance on air temperature, mean radiant temperature, plane radiant temperature, absolute humidity, air velocity, surface temperature, operative temperature and natural wet‑bulb temperature.

Practical applications and who uses ISO 7726:2025

• Instrument manufacturers - to design and certify measurement devices that meet minimum ergonomics and thermal monitoring requirements.
• HVAC engineers and building designers - for accurate assessment of thermal comfort and system performance.
• Ergonomists and occupational health professionals - to evaluate worker exposure, thermal stress, and compliance with workplace guidance.
• Environmental consultants and researchers - for standardized data collection in field studies and laboratory experiments.
• Regulatory bodies and contract managers - to define measurement specifications in procurement and compliance documents.

Related standards

• ISO 13731 (Vocabulary and symbols for ergonomics of the thermal environment) is normative for terms and definitions used in ISO 7726:2025.
• ISO 7726 is part of a wider suite of standards addressing ergonomics of the thermal environment and should be used alongside interpretation and exposure-limits documents in that group.

Using ISO 7726:2025 helps ensure consistent, reproducible thermal-environment measurements - a foundation for reliable thermal comfort assessment, risk evaluation and HVAC optimization.