Using Regional Data and Building Leakage to Assess Indoor Concentrations of Particles of Outdoor Origin

Figures & data

TABLE 1 Model for inputs to mass balance analysis

Modeling Approach	1: Detailed	2: Central Site with Measured ACH	3: Central Site Only Input Parameter
Input Parameter
P	0.75	0.75	0.75
K dep	0.2 hr^− 1	0.2 hr^− 1	0.2 hr^− 1
K evap	varies with indoor temperature	4.6 hr^− 1 for Oct 1.6 hr^− 1 for Dec-Jan	4.6 hr^− 1 for Oct 1.6 hr^− 1 for Dec-Jan
Initialization
Indoor sulfate and black carbon	Measured	50% of Central Site Concentration	50% of Central Site Concentration
Indoor nitrate	Measured	20% of Central Site Concentration	20% of Central Site Concentration
Outdoor Concentration	Measured	Equal to Central Site Concentration	Equal to Central Site Concentration
Air Exchange Rate	Measured	Measured	LBL infiltration model

FIG. 1 Indoor, outdoor, and central site concentrations of black carbon, sulfate, and nitrate, together with the air exchange rate inside the Clovis Study House, during a period when the ventilation rates were purposely manipulated.

FIG. 2 Indoor, outdoor, and central site concentrations of black carbon and nitrate during the period between the Christmas and New Years holidays when the house was unoccupied with doors and windows closed.

TABLE 2 Comparison of filter and continuous measurements ¹

	Central Site/Outdoor	Outdoor/Indoor
Black Carbon
Continuous	1.57	1.85
Filter	2.28	1.63
Sulfate
Continuous	0.96	1.92
Filter	0.97	1.79
Nitrate
Continuous	0.71	10.96
Filter	0.61	9.04

FIG. 3 Comparison air exchange rates estimated using the LBNL infiltration model to that measured by SF₆ tracer gas methods, showing the variation with the indoor-outdoor temperature difference. (Occasional spikes in measurements coincide with opening of doors to service instruments.)

FIG. 4 Modeled indoor concentrations of black carbon, sulfate, and nitrate calculated using the three approaches outlined in Table 1, with comparison to measured values. Results are for one week of measurements during the fall study period when doors and windows in the house were closed. For nitrate, results are also given for Model 1 when the evaporation term is set to zero.

FIG. 5 Modeled indoor concentrations of black carbon, sulfate, and nitrate obtained from the three approaches outlined in Table 1, with comparison to measured values, during wintertime closed-house measurements. For nitrate, results are also given for Model 1 when the evaporation term is set to zero.

TABLE 3 Comparison of measured and modeled concentrations from differing model inputs¹

	Fall study (μg/m^3)	Winter study (μ g/m^3)
Black Carbon
Measured Ambient and Indoor Concentrations (mean):
Central Site (ambient measurement)	1.8	5.2
Outdoors (immediately outside the study house)	0.86	4.7
Indoors	0.43	2.5
Modeled Indoor Concentrations (mean):
Model 1: Detailed	0.41	1.83
Model 2: Central Site with Measured ACH	0.87	2.18
Model 3: Central Site only (ACH from LBNL infiltration model)	0.85	2.54
RMS Error (Modeled–Measured) ^1
Model 1: Detailed	0.10	1.3
Model 2: Central Site with Measured ACH	0.56	0.84
Model 3: Central Site only (ACH from LBNL infiltration model)	0.54	0.91
Sulfate
Measured Ambient and Indoor Concentrations (mean):
Central Site	1.1	1.7
Outdoors	0.9
Indoors	0.42	0.58
Modeled Indoor Concentrations (mean):
Model 1: Detailed	0.43	—
Model 2: Central Site with Measured ACH	0.56	0.70
Model 3: Central Site only (ACH from LBNL infiltration model)	0.54	0.82
RMS Error (Modeled–Measured) ^1
Model 1: Detailed	0.12
Model 2: Central Site with Measured ACH	0.21	0.23
Model 3: Central Site only (ACH from LBNL infiltration model)	0.19	0.30
Nitrate
Measured Ambient and Indoor Concentrations (mean):
Central Site	6.2	17.
Outdoors	6.5	29.
Indoors	0.22	2.7
Modeled Indoor Concentrations (mean):
Model 1: Detailed	0.37	2.61
Model 2: Central Site with Measured ACH	0.34	1.49
Model 3: Central Site only (ACH from LBNL infiltration model)	0.31	2.05
Neglecting evaporation, but otherwise with detail input of Model 1	3.11	11.56
RMS Error (Modeled–Measured) ^1
Model 1: Detailed	0.25	1.0
Model 2: Central Site with Measured ACH, k evap varies with T in )	0.19	2.0
Model 3: Central Site only (modeled ACH, k evap constant)	0.16	1.5

FIG. 6 Histograms of the difference between modeled and measured indoor concentrations of black carbon, sulfate, and nitrate for the three modeling approaches outlined in Table 1. Model (1) uses measured air exchange rates, nitrate evaporation calculated from measured indoor temperatures and ambient concentrations measured immediately outside the house; model (2) uses outdoor concentrations from the central monitoring site and measured air exchange rages and (3) using central site data only, with air exchange rates estimated from the LBNL infiltration model. Penetration = 0.75, deposition = 0.2 hr^{− 1} for all scenarios. Data are from fall and winter study periods when windows and doors to the house were closed (October 10 midnight–October 16 noon, December 22 midnight–December 29 noon, December 31 noon–January 15 midnight).

FIG. 7 Comparison of regression coefficient squared (R²) and regression slope for linear fits of each of the three model calculations, the proximate outdoor concentration and the central site concentration to the hourly averaged indoor concentrations for black carbon, nitrate, and sulfate. Data are shown for black carbon, nitrate, and sulfate during a one-week period in October, and for black carbon and nitrate for a two-week period in January, when the house was unoccupied with windows and doors shut.

TABLE A1 Shielding and terrain class model constants

Class	C	Description
Shielding classes
I	0.34	No obstructions or local shielding whatsoever
II	0.30	Light local shielding with few obstructions
III	0.25	Moderate local shielding, some obstructions within two house heights
IV	0.19	Heavy shielding, obstructions around most of perimeter
V	0.11	Very heavy shielding, large obstructions surrounding perimeter within two house heights.
Class	A	B   Description
Terrain classes
I	1.30	0.10   Ocean or other body of water with at least 5 km of unrestricted expanse
II	1.00	0.15   Flat terrain with some isolated obstacles (buildings and/or trees well separated from each other)
III	0.85	0.20   Rural areas with low buildings and/or trees
IV	0.67	0.25   Urban, industrial or forested area
V	0.47	0.35   Center of large city (e.g., Manhattan)

TABLE A2 Stack and wind factors for terrain class IV for a one-story structure (H = 2.5 m)

	Leakage Distribution Factors
Stack factor	X	R = 0.7	R = 0.5	R = 0.3
f s	X = R	0.078	0.101	0.106
	X = 0.8 R	0.096	0.108	0.108
	X = 0.5 R	0.116	0.115	0.110
Wind factor	Shielding class
f w	III: C = .24	0.076	0.090	0.101
	IV: C = .19	0.060	0.071	0.080
	V: C = .11	0.035	0.041	0.046