Certified Respiratory Therapist Practice Exam

How long will an H-cylinder of oxygen last if it has 1100 psig and is emptying at a flow of 8L/min?

1. 4.5 hours

2. 6.0 hours

3. 7.2 hours

4. 9.0 hours

The correct answer is: 7.2 hours

To determine how long an H-cylinder of oxygen will last when it has a pressure of 1100 psig and is being depleted at a flow rate of 8 liters per minute, you can use the following steps: First, it's essential to know the capacity of the H-cylinder. An H-cylinder typically contains approximately 2440 liters of oxygen when full at 2000 psig. To find the amount of oxygen remaining at 1100 psig, we can use the formula that correlates the pressure in the cylinder to the volume of gas. The remaining volume can be calculated as follows: 1. **Calculate the percentage of gas remaining:** \[ \text{Remaining volume} = (1100 \text{ psig} / 2000 \text{ psig}) \times 2440 \text{ liters} \] 2. **Perform the calculation:** \[ \text{Remaining volume} = 0.55 \times 2440 \approx 1342 \text{ liters} \] Next, with 1342 liters still available and knowing that the flow rate is 8 liters per minute, you can determine how long the oxygen will last by dividing the