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What's the hole for in an airplane’s windows?

Published on 25/10/2015 01:00 - By

If you have already taken the window seat in an airplane, you may have noticed a small hole in the glass, and probably wondered what it was for.

The windows in an aircraft consist of (at least) one outer and inner pane (much like double glazed windows). The little hole, of about 2 mm in diameter, which we can see, is only in the window’s inner pane, and therefore not connected to the outside of the aircraft.

The inner pane, called a decorative porthole, is itself protected on the passenger side by a transparent plastic sheet for safety reasons. The inner and outer panes are made of acrylic, (polymethyl methacrylate or PMMA), according to data from the French aircraft window manufacturer, Saint-Gobain.

The small hole, or breather hole, helps to equalize the air pressure and temperature between the two panes and those in the cabin. A pressure difference would weaken the inner pane, and a temperature difference could cause fogging up, or condensation, inside the window.

Our camera and mike recorded your answers at an airport that are, on the whole, not entirely wrong.

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