Certified Respiratory Therapist Exam 2025 – 400 Free Practice Questions to Pass the Exam

To determine the approximate total output flow from a 35% air-entrainment mask operating at a flow rate of 8 L/min, it's essential to understand how air-entrainment masks work. These devices mix oxygen with room air to achieve a desired oxygen concentration, in this case, 35%.

The total output flow from an air-entrainment mask can be calculated by the formula:

Total Output Flow = Flow Rate + (Flow Rate x (air to oxygen ratio))

For a 35% mask, the air-to-oxygen ratio is typically around 3:1, meaning for every part of oxygen, three parts of room air are entrained. When you calculate the total output for a mask like this:

1. The air entering is approximately three times the oxygen flow.

2. Therefore, for a flow-rate of 8 L/min set for oxygen, the flow of air mixed with this would be 3 times that amount, or 24 L/min of air.

Adding this to the 8 L/min of oxygen provides the total output flow:

Total Output Flow = 8 L/min (oxygen) + 24 L/min (air) = 32 L/min.

However, the question asked for an approximation,