Air Brake Coach
System partsQuestion 7 of 116

What does the desiccant in a modern air dryer do?

  1. It adds oil to the air
  2. It cools the brake drums
  3. It raises the air pressure
  4. It adsorbs moisture from the air
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Correct answer: It adsorbs moisture from the air

Desiccant adsorbs moisture as the air passes by. The dryer then blows the moisture out during a purge.

Source: Air Brake Manual: A Guide for Instructors (Government of Alberta, Alberta Transportation, March/April 2012), Module 3: Supply circuit, page 44

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Questions last reviewed: 18 October 2026