ASHRAE
The engineering society whose thermal guidelines define the temperature and humidity envelopes for IT equipment.
Current numbers
G0-2019 / G1.1-2025 / Std 202-2024; G1.6P in first public review (Oct 2026)Published ASHRAE commissioning references and the data-center guideline now in public review; freeze the editions you adopt
Addendum b approved 27 February 2026ASHRAE CDU test and rating boundary: external head and electrical inputs
18–27 °CASHRAE A1–A4 recommended inlet band; allowable A1 15–32, A2 10–35, A3 5–40, A4 5–45 °C; H1 18–22 recommended, 15–25 allowable