A classroom measurement gives 300 cfm of outdoor air and a room volume of 9,000 ft³. What outdoor-air change rate results?
- A0.033 ACH
- 2 ACH
- C30 ACH
- D1,800 ACH
Where to look it up
https://www.cdc.gov/niosh/ventilation/faq/index.html
Why B is correct
300 × 60 / 9,000 = 2 ACH. The 60 converts minutes to hours. This is a measured-rate calculation, not a Texas classroom minimum.