If you’ve ever been on an airplane, you may have noticed the little ‘hole’ in airplane windows. This hole is called a bleeding hole or a breathing hole. But have you ever wondered what this hole is for?
WHAT DOES THE HOLE IN THE AIRCRAFT WINDOWS DO?
According to aviation experts, the small opening in the window of commercial passenger planes, known as the breath hole, is actually an important safety feature. The hole helps regulate how much pressure is applied to the window panes from the cabin and ensures that if the glass is to break, the outer glass will break first.
A hole in the middle chamber helps direct cabin pressure to the outer chamber. If the outer glass bursts or cracks, the inner glass can maintain this pressure.
Insider says the FAA responded:
Airplanes are designed to keep the air pressure in the cabin at a safe level. The difference in air pressure inside and outside the cabin puts too much physical pressure on the airplane window.
Airplane windows consist of three separate panes. The outermost part takes care of this air pressure difference and makes use of tiny holes in the middle known as “bleed holes”. Its primary purpose is to balance air pressure. There is a small gap between the middle and outer windows.
The breathing hole, also known as the bleed hole, allows the pressure to be balanced between the passenger compartment and the air gap. That is, the outer chamber assumes the pressure, while the middle chamber acts as a fail-safe. The task of the inner glass layer is to help protect the middle and outer compartments from damage caused by passengers. In other words, it protects the layers that come after it. The “air hole” also releases moisture from the air gap. This prevents the glass from fogging up or icing up.
Therefore, in order for it to do its job properly, the vent must not be touched or covered in any way.
This question was brought up again when Robbie Gonzalez of iO9 was directed to Marlowe Moncur, director of technology at GKN Aerospace.
A patent filed by Daimlerchrysler Aerospace Airbus in 1997 explains that this “air duct” helps maintain the “outside atmospheric pressure” inside the windows. Air is pressurized by engines that compress it as it moves through a series of fans in the aircraft. This incoming air is retained in the cabin using an outlet valve to maintain cabin pressure even at high altitudes.
You can liken this system to the way a tire is inflated in automobiles. High-pressure air is “pumped” into the cabin and this air comes from the compression stage of the engines.
Sensors measure how much pressure is in the cabin, and this valve releases air at a rate that maintains that pressure. For example, this valve is open when the aircraft is stationary. It only starts to turn off when the plane is taking off. Due to the lack of oxygen at high altitudes, the airplane needs to be pressurized to keep it comfortable and safe for passengers.
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