Tag Archives: pressure regulator

Airplane Oxygen Pressure

Welcome to All Sensors “Put the Pressure on Us” blog. This blog brings out pressure sensor aspects in a variety of applications inspired by headlines, consumer and industry requirements, market research, government activities and you. In this blog we’ll discuss airplane oxygen pressure.

Airplane Oxygen Pressure

You hear it every time you fly on a commercial airline: “If a drop in cabin pressure occurs, oxygen masks will drop down. Oxygen is flowing even though the bag does not inflate.”

oxygenmask

As a pressure sensing proponent, this raises three questions: What is the tank pressure? What is the line pressure? What pressure drop occurs in the line?

While aviation regulations require that an emergency oxygen supply is available to passengers if there is a loss of cabin pressure, storing oxygen in tanks would add weight, complexity and maintenance issues to those already required for each airplane. As a result, the majority of commercial aircraft use chemical oxygen generators to provide emergency oxygen for passenger cabin occupants. Pulling down the oxygen mask releases the firing pin and activates the generator.

With this process, the three pressure sensing questions are moot. However, there are other pressure issues involved.

According to “Chapter 16: Cabin Environmental Control Systems,” “At sea level, oxygen pressure in the lungs is approximately three pounds per square inch (psi).” Without supplemental oxygen, this level drops to 1.74 psi at 15,000 mean sea level (MSL) and oxygen transfer to the bloodstream drops to 81% of saturation, typically resulting in sleepiness, headache, blue lips and fingernails, and increased pulse and respiration.

Pressurizing the passenger compartment avoids the problem of lower oxygen transfer – until a loss in cabin pressure occurs. In addition to the chemical oxygen generators, oxygen tanks are usually used for the crew in commercial airplanes and other non-commercial airplanes. The storage tanks have different rated pressures.

Certification Type Material Rated pressure (psi)
DOT 34A Steel 1,800
DOT 3HT Steel 1,850
DOT-E-8162 Composite 1,850
DOT-SP-8162 Composite 1,850
DOT 3AL Aluminum 2,216

In the oxygen tank system, a pressure regulator lowers the oxygen pressure from the storage cylinder(s) to approximately 60 to 85 psi and delivers it to individual regulators dedicated for each user where further pressure reduction occurs.

So sit back and relax. There are many reasons why flying is among the safest ways to travel.

What do you think/Comments?
Do you have a pressure sensing question? Let me know and I’ll address it in an upcoming blog.
-Han Mai, Marketing Coordinator, All Sensors Corporation (hmai@allsensors.com)