Which of the following statements about breathing air systems is NOT true?

The statement that there are three breathing air cylinders located on the top of the apparatus is not universally true because the number and location of breathing air cylinders can vary depending on the specific design and configuration of the fire apparatus. While many fire vehicles may carry multiple breathing air cylinders, the exact number and placement can differ by manufacturer, departmental needs, or model. Hence, stating that there are specifically three cylinders on top of all apparatuses misrepresents the standardization of breathing air systems, as some may have different capacities or be positioned differently.

In contrast, the other options regarding breathing air systems are accurate. They do serve the critical function of providing breathable air in environments that are hazardous to health, such as during firefighting operations, and they are vital for ensuring firefighter safety. Additionally, regular maintenance checks are essential to ensure the reliability and functionality of these systems, which are fundamental to maintaining operational readiness and ensuring the safety of personnel in dangerous situations.