Commercial Pilot License (CPL) Practice Exam 2025 - Free Commercial Pilot License Practice Questions and Study Guide

For aircraft certified to fly between 35,000 and 45,000 feet, the requirement for a pressure-demand mask is based on the need to provide adequate oxygen at higher altitudes where the atmospheric pressure is significantly lower. At these altitudes, the partial pressure of oxygen decreases, making it essential to deliver oxygen in a way that ensures the pilot receives sufficient amounts to breathe normally.

The pressure-demand mask provides a continuous flow of oxygen as the wearer inhales while also maintaining a positive pressure in the mask. This is crucial for preventing hypoxia in pilots operating at high altitudes, where oxygen availability is significantly reduced. Additionally, pressure-demand masks can prevent the inhalation of outside air, which could be harmful at such altitudes due to the lower oxygen levels and potential contaminants.

Other types of masks, such as diluter-demand and continuous flow masks, are not suitable for these altitude ranges due to their inability to supply sufficient oxygen in the low-pressure environment. Continuous flow masks can only deliver a set amount of oxygen, regardless of the pilot’s breathing demands, which may not meet the requirements at high altitudes. Therefore, the pressure-demand mask is the only choice that fits the needs of pilots operating in this specific altitude range.