Table.

The following pressure readings, noise level, and air changes per hour were obtained during the tests.^∗

No. of HEPA Units Operating	Power Level	Pressure Readings Pa (Inches of Water)	Noise Levels, dB	Air Changes per Hour (Calculated)
1	High	−1.5 (−0.006)	Not tested	4.1
2	High	−4.5 (−0.018)	74	8.2
3	High	−8.0 (−0.032)	Not tested	12.3
4	High	−13.0 (−0.052)	76	16.4
4	Low	−8.0 (−0.032)	70	8.2

^∗Calculations of air changes per hour are number of units × (2,000 cubic feet per minute [cfm] on high setting or 1,000 cfm on low setting) × 60 minutes divided by 29,300 (cubic feet of room). Example based on 4 units on high setting: (4 units × 2,000 cfm × 60 minutes) ÷ 29,300 = 16.4 air changes/hour.