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Indoor VOC's

Indoor Minus Outdoor VOC Concentrations in Call Center
Since the primary focus was on contamination sources associated with the building and occupants, indoor minus outdoor (In-Out) VOC and CO2 concentrations were calculated and are shown in Table 5.

Table 5 Indoor minus outdoor (In-Out) concentrations and emission factors of the 10 most abundant VOCs and CO2 in a call center.
  Concentration (ppb)   Emission Factora
  Outdoor In-Out In-Out Precision (µg m-2 h-1)
Compound Median Median Range (%) Median Range
Ethanol
  		9.0
  		26
  		7.0-112
  		12
  		380
  		153-780
 
2-Propanol
  		9.8
  		29
  		8.7-240
  		5
  		550
  		94-2,400
 
2-Butoxyethanol
  		1.2
  		2.6
  		0.7-17.8
  		4
  		62
  		14.7-990
 
Acetone
  		4.9
  		9.8
  		2.1-39
  		46
  		190
  		29-410
 
Formaldehyde
  		4.4
  		6.2
  		3.1-20
  		<15
  		40
  		20-174
 
Acetaldehyde
  		1.7
  		1.5
  		<0.1-3.2
  		<15
  		16.2
  		6.2-30
 
Hexanal
  		0.3
  		0.9
  		0.3-1.9
  		15
  		21
  		13.0-48
 
Isoprene
  		0.1
  		0.6
  		<0.1-2.6
  		22
  		10.9
  		5.5-28
 
d-Limonene
  		<0.1
  		0.8
  		0.2-4.9
  		4
  		27
  		17.0-79
 
D5 Siloxaneb
  		<0.1
  		2.3
  		1.0-7.4
  		6
  		230
  		114-300
 
CO2
(ppm, mg m-2 h-1) 		  210 122-510 -- 56 35-80
a Summary for 21 samples collected near steady-state conditions

b D5 = decamethylcyclopentasiloxane

Only ten VOCs had median In-Out concentrations for the 28 samples in excess of 0.5 ppb. With the exception of formaldehyde and acetaldehyde, the In-Out median values for these 10 exceeded their median outdoor concentrations by a factor of two or more. There were at least 6-fold variations in individual VOC concentrations with space and time among the 7 days. VOC emission factors (mass emitted per unit area per hour in µg/m2-h) also were calculated for the 21 samples that were collected near steady-state conditions. The solvents ethanol, isopropanol and acetone had the highest emission factors. The D5 siloxane (decamethylcyclopentasiloxane) is used in personal deodorants and previously has been associated with building occupancy.

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