For a responsive, breathing person receiving oxygen via a non-rebreather mask, how should you react if fluids start to collect in the mask?

Removing the mask and allowing drainage in the recovery position is the most appropriate response when fluids collect in a non-rebreather mask. This action is crucial because it addresses the immediate issue of fluid accumulation that can impair effective oxygen delivery. By placing the person in the recovery position, any fluids can drain out of the mask, preventing choking or additional respiratory distress.

The recovery position also helps maintain an open airway while ensuring that the individual remains stable and can continue to breathe comfortably. It is essential to monitor the person's airway and breathing throughout this process since clearing the mask of fluids is crucial for ongoing oxygen therapy to be effective.

Other options may not provide the best immediate care. For instance, switching to a simple face mask and lowering the flow could compromise the oxygen delivery, especially if the non-rebreather was being used for a critical respiratory condition. Waiting without changing the setup ignores the potential risk of fluid-related complications, and repositioning the individual flat on their back could risk airway obstruction due to fluid accumulation.