Hong Kong typhoon season means windows should stay shut: the risks otherwise are too high

I refer to the letter from John Fleming (“Pressure on for an answer over typhoon advice”, October 30) regarding how to minimise household damage brought about by air pressure under high winds. 

Ferocious winds of an intense typhoon like Mangkhut can cause a noticeable pressure difference inside and outside a building, and this accounts for the difficulty that Mr Fleming encountered in opening the front door of his flat. This can be explained by way of Bernoulli’s principle, which is the scientific cause of the force lifting the wing of an aircraft when air of different speeds flows along the two surfaces of the wing.

Although leaving a window slightly open could help better balance the pressure inside and outside the building, doing so would increase the risk of ferocious winds and rain funnelling through the gap. The fierce winds during a typhoon might also cause the open window to vibrate, increasing the risk of damage and associated danger to the people indoors.

Repairing properties mauled by Typhoon Mangkhut won’t be cheap

Members of the public are therefore advised to check that their windows and air conditioners are secure before the tropical cyclone season, and to shut and lock the windows securely during the passage of a tropical cyclone.

Lee Lap Shun, senior scientific officer, Hong Kong Observatory