We test our windows by exposing them to winds so highthat it is not found on the Danish wind force scale. Firstly, we expose the window to a positive pressure of up to 2,400 Pa and then to a negative pressure down to minus 2,400Pa.This is equivalent to the pressure which a window is exposed to during a strong hurricane. Then we expose the window to stress by switching fast between positive pressure and negative pressure. Finally, we check the panes or frames for damage. So we are not afraid to say that we test the robustness of our windows to the limit.