What is the expected change in oxygen reading for every 40 meters descended in a shaft?

The expected change in oxygen reading for every 40 meters descended in a shaft is an increase of approximately 0.1%. This phenomenon is primarily due to the increase in atmospheric pressure as one descends deeper underground.

At sea level, the percentage of oxygen in the air is approximately 21%. However, as you descend into a mine or shaft, the pressure increases, and while the actual concentration of oxygen (in percentage terms) does not significantly change, the partial pressure of oxygen does increase because it is part of a higher total atmospheric pressure. This increase in pressure allows for a greater partial pressure of the gases, including oxygen, which is why we see a slight increase in the oxygen reading at a depth of 40 meters.

Understanding the relationship between pressure and gas concentration is crucial in fields that involve deep mining or underground work. This concept reflects principles of gas laws and is important for ensuring safety in environments with potentially hazardous atmospheric conditions.