Measuring airflow through the portable high-efficiency air filtration (PHEAF) device to assess reliability of instrument and sample location

Figures & data

Figure 1. Diagram of PHEAF device showing major components.

Table 1. Summary of volumetric airflow for PHEAF manufacturer models measured by hot wire anemometer or balometer.

		N		Mean intake, cfm (SD)		Mean exhaust, cfm (SD)		Percent reduction from manufacturer’s stated airflow (SD)^+
PHEAF manufacturer model	Manufacturer stated airflow, cfm	Hot wire anemometer	Balometer	Hot wire anemometer	Balometer	Hot wire anemometer	Balometer	Hot wire anemometer	Balometer
D	1900	0	7	**	929.1	**	1033.6	**	48.3
					(201.4)		(253.9)		(11.9)
E	1975	126	155	1025.6	1193.2	1229.7	1308.7	42.9	36.8
				(402.4)	(398.0)	(562.3)	(426.9)	(21.9)	(21.0)
F	1000	6	0	977.5 (257.3)	*	1129.3 (217.6)	*	−5.3 (19.7)	*
H	2100	7	14	1025.4	1304.8	2284.9	1510.0	21.2	33.0
				(211.3)	(187.1)	(595.6)	(222.4)	(14.0)	(9.5)

⁺The percent reduction is computed using the average of the intake and exhaust measurements.

*Surface area of PHEAF unit was not of sufficient size for balometer measurement to seal again the unit’s cabinet.

**PHEAF units were not available during the period hot wire anemometer data were collected.

Figure 2. Distribution of hot wire anemometer and balometer readings in this study, grouped by location, for PHEAF model E. The vertical line denotes the manufacturer’s advertised capacity of 1975 cfm.

Table 2. Estimates of measurement error for different volume measurement techniques (PHEAF manufacturer model E).

Measurement technique	Within-unit SD	95% Confidence interval
Intake volume hot wire anemometer	252.1	241.7–295.9
Exhaust volume hot wire anemometer	409.8	349.2–480.9
Center sector volume hot wire anemometer	228.4	194.4–268.2
Intake volume balometer	272.4	238.6–310.9
Exhaust volume balometer	303.1	265.4–346.1

Table 3. Face velocities (feet per minute) measured at nine filter sectors on PHEAF manufacturer model E, mean (coefficient of variation) (n = 126 measurements per sector).

Sector 1	Sector 2	Sector 3
295.0	297.2	296.8
(43.9)	(41.3)	(41.6)
Sector 4	Sector 5	Sector 6
287.2	279.2	287.3
(42.9)	(37.8)	(40.6)
Sector 7	Sector 8	Sector 9
290.2	283.2	285.5
(42.1)	(38.6)	(40.3)

Figure 3. Simple linear regression model of intake volume and exhaust volume as measured by hot wire anemometer for PHEAF model E.

Figure 4. Simple linear regression model of intake volume and exhaust volume as measured by balometer for PHEAF model E.

Table 4. Effect of volume measurement on percent capture efficiency when particle penetration is measured at 10%.

Parameter	Hot wire anemometer	Balometer
Airflow	1025 cfm	1308 cfm
Photometer 100% setting	26 mg/m^3 (calculated)	21 mg/m^3 (corrected)
Photometer reading	10.0% (observed)	12.38% (corrected)
% Capture efficiency	100% − 10.0% = 90.0%	100% − 12.38% = 87.62%