One Air, Two Appetites

Every technology has a humidity envelope with failure at both edges — ASHRAE puts a data centre between 5.5 and 15°C dew point and 40–60% RH, static below, corrosion above. That claim is right and general. Two corrections follow: vapor pressure deficit is the wrong variable for dry hardware, because it measures evaporation from a wet surface; and the moss and the machine want opposite air. What…