# The Pressure Impact from Higher to Lower Altitudes

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 pressure and the difference in impact from high to lower altitudes.

### The Pressure Impact from Higher to Lower Altitudes

If you have ever driven from a high altitude, say 5000’ above sea level to about 1000’, and you have a flexible sealed empty bottle in the car, at some point, you notice the creaking sound as the bottle collapses due to lower atmospheric pressure sealed inside and higher atmospheric pressure outside.  With the sound effect, the pressure increase on the sealed bottle taken from higher to lower altitude is quite noticeable. Obviously the pressure decreases (externally) during the reverse process and a gas tank (or other similar sealed vessel) taken to a higher altitude winds up visibly expanding.

This is just one example of the impact of altitude pressure. Athletes performing at higher altitudes know that the altitude affects their performance, especially their endurance, since high altitude (HA) causes faster and deeper breathing. Altitude also affects sleep and cardiac output, so those accustomed to living at lower altitudes need to take appropriate precautions to adjust to the change. Training at higher altitudes can actually enhance the performance of athletes when they compete at lower altitudes.

Humans aren’t alone in their need to adjust to altitude. Internal combustion vehicles must adjust to altitude as well. When electronics was first used to adjust spark and fuel to reduce emissions and improve fuel economy, carmakers used barometric pressure sensors to adjust for altitude.

The pressure change from one altitude to another can be calculated by calculating the pressure for each altitude and then subtracting.  Air pressure above sea level is:

p = 101325 (1 – 2.25577 10-5 h)5.25588

where,

p = air pressure (in Pa)

h = altitude above sea level (in m)

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)