[EN 16798-3:2017, 3.13]:reference conditions for pressure drop are: Clean filters and dry conditions for other components (e.g. heat exchanger, cooling coil and humidifier).

[EN 12792:2003, 298]:test ratio between the pressure suction effect and the pressure due to an air velocity passing over a cowl or roof outlet.

[EN 12792:2003, 300]:maximum pressure difference at which the rated watertightness is assured under test conditions.