Indoor Sources of Ultrafine and Accumulation Mode Particles: Size Distributions, Size-Resolved Concentrations, and Source Strengths

Figures & data

FIG. 1 Indoor number concentrations while indoor sources are active compared to concentrations due to outdoor particle infiltration. Error bars on means are standard errors.

TABLE 1 Number concentrations (cm^{− 3}) for six size ranges

Size (nm)	N	Mean	SD	SE	Maximum
Indoor Source
10–18	31371	4589	7382	42	115384
18–50	45185	10101	14312	67	277945
50–100	45185	6045	11431	54	198567
100–200	45185	2238	4346	20	78876
200–450	45299	405	1011	5	78576
450–950	14110	63	321	3	19186
Outdoor source
10–18	142474	337	407	1	6969
18–50	213104	1162	1136	2	8799
50–100	213104	1057	898	2	12073
100–200	213104	680	571	1	6124
200–450	213352	180	216	0	8442
450–950	72300	18	36	0	2826
Total
10–18	174092	1109	3557	8.5	115384
18–50	258812	2730	6955	14	277945
50–100	258812	1936	5206	10	198567
100–200	258812	955	1981	3.9	78876
200–450	259174	219	474	0.9	78576
450–950	86611	25	135	0.5	19186

TABLE 2 Indoor and outdoor contributions to particle number concentrations (cm^{− 3})

Size (nm)	N	Total	Outdoor	Indoor	Outdoor contribution (%)
10–18	174092	1109	337	772	30
18–50	258812	2730	1162	1568	43
50–100	258812	1936	1057	879	55
100–200	258812	955	680	275	71
200–450	259174	219	180	40	82
450–950	86611	25	18	7	70

TABLE 3 Number and duration ^a of 18 selected activities, with modal diameters for both particle number and volume

			Modal diameter (nm)
Activity	Number of events	Average duration (min)	Number	Volume
Gas clothes dryer	68	179	< 10	181
Tea & toast	375	33	< 10	51
Tea	36	31	11	46
Breakfast	149	33	11	66
Stir-fry	24	131	36	118
Unknown indoor sources	451	80	36	131
Dinner	225	83	39	181
Fried eggs	41	51	40	181
Unknown outdoor sources	174	207	40	429
Gas oven	58	19	45	95
Broiled fish, baked potato	217	53	46	98
Citronella candle	54	167	46	638
Open windows	52	120	53	241
Tortillas	221	48	64	146
Incense	11	114	64	250
Outdoors	502	31	69	168
Smoky cooking oil	5	128	69	233
No indoor sources	888	1188	69	269

TABLE 4 Size-resolved particle number (cm)^{− 3} produced by 18 activities

	Diameter (nm)
Activity	10–100	100–200	200–450	450–950	Total
No indoor sources	2557	683	183	18	3441
Tea	5763	58			5821
Citronella candle	3135	1613	1634	576	6958
Open windows	7585	864	150	3	8601
Tea & toast	9527	1			9528
Incense	6681	2309	722		9713
Unknown outdoor sources	9049	1074	222	34	10379
Outdoors	9522	18352	3030	16	11675
Breakfast	19966	117		13	20096
Unknown indoor sources	21432	1068	100	12	22611
Fried eggs	22507	2199	317	53	25077
Stir-fry	25375	1643	142	14	27174
Gas clothes dryer	27242	700	66	5	28013
Gas oven	29735	1395	68	21	31219
Dinner	30456	2311	321	41	33129
Smoky cooking oil	33509	8660	1516	132	43817
Tortillas	39700	8387	823	72	48982
Broiled fish	47230	2627	98	17	49972

TABLE 5 Size-resolved particle volume (μm/cm)³due to 18 activities

	Diameter (nm)
Activity	10–100	100–200	200–450	450–950	Total
Tea	0.08	0.06			0.14
Tea & toast	0.18				0.18
Breakfast	0.46	0.10		1.19	1.74
Gas clothes dryer	0.87	0.89	0.44	0.61	2.81
Open windows	0.59	1.17	1.28	0.52	3.56
Unknown indoor sources	1.11	1.31	0.88	1.46	4.76
No indoor sources	0.26	1.01	1.99	1.81	5.07
Stir-fry	1.51	1.82	1.20	2.08	6.62
Gas oven	2.15	1.42	1.02	2.72	7.31
Outdoors	0.88	2.53	2.72	1.80	7.62
Unknown outdoor source	0.64	1.49	2.52	3.68	8.32
Broiled fish	3.54	2.77	0.88	2.43	9.61
Incense	0.69	3.67	6.74		11.10
Dinner	1.94	2.97	3.34	4.68	12.93
Fried eggs	1.55	2.89	3.43	6.31	14.18
Tortillas	5.01	10.54	7.26	8.53	31.35
Smoky cooking oil	4.71	11.52	16.95	15.39	48.57
Citronella candle	0.25	2.99	24.29	70.96	98.50

FIG. 2 Size distributions of outdoor particles measured outdoors and indoors. “No indoor sources” refers to indoor measurements showing no influence of indoor sources. “Open windows” refers to indoor measurements made with windows open. “Unknown outdoor source” refers to indoor measurements showing slow increases typical of slow outdoor changes in concentration, with no apparent indoor source. “Outdoors” refers to measurements made outdoors. Discontinuities at 18 nm and 440 nm in this and following figures are due to different ranges associated with the two nozzle assemblies.

FIG. 3 Size distributions of particles created by the gas burner only (boiling water for tea) and the gas burner and electric toaster or toaster oven.

FIG. 4 Size distribution of particles created by frying using cooking oils.

FIG. 5 Size distributions of particles created by using the gas oven.

FIG. 6 Size distributions of particles created by burning incense or a Citronella candle.

FIG. 7 Size distribution of particles created by a gas clothes dryer.

TABLE 6 Variation of infiltrated outdoor particle number concentration (cm^{− 3}) by size category and by year

Year	10–18 nm	SE	18–50 nm	SE	50–100 nm	SE	100–200 nm	SE	200–450 nm	SE	450–950 nm	SE	N (10–18 nm)	N (18–450 nm)	N (450–950 nm)
1998	239	1	1019	4	1069	4	616	2	129	0			50027	50069	0
1999	393	2	1338	4	1249	4	834	2	236	1	21	0	43058	78291	36089
2000	407	2	1101	4	882	3	573	2	165	1	15	0	41376	77254	35459

TABLE 7 Variation of infiltrated outdoor particle number concentration (cm^{− 3}) by size category and by month

Month	10–18 nm	SE	18–50 nm	SE	50–100 nm	SE	100–200 nm	SE	200–450 nm	SE	450–950 nm	SE	N (10–18 nm)	N (18–450 nm)	N (450– 950 nm)
January	413	3	1415	8	1200	7	645	3	119	1	11	1	19037	20016	2356
February	380	3	1371	8	1226	6	733	4	162	1	18	0	15495	19480	3983
March	329	3	1196	8	964	5	512	3	112	1	8	0	15251	19939	4544
April	309	4	1310	9	1147	6	648	3	170	1	11	0	8427	20157	11841
May	315	3	1290	9	1316	7	808	4	226	2	20	0	11297	19589	8283
June	249	4	892	9	937	7	724	5	221	2	28	1	10490	14625	4166
July	341	4	948	9	990	8	724	5	155	1	17	1	12789	13293	562
August	313	4	1077	9	1010	7	795	5	310	3	38	1	9745	17989	8231
September	238	4	924	8	961	7	789	6	280	3	30	1	9815	16754	6789
October	328	7	926	8	748	6	521	4	169	2	9	0	5021	14321	9173
November	383	4	1040	8	857	6	532	4	118	1	14	0	11772	15101	3174
December	347	3	1265	7	1115	6	704	4	133	1	7	0	13335	21840	8446
Winter-Spring (Dec–May)	349	8	1308	20	1161	16	675	9	154	3	13	1
Summer-Fall (June–November)	309	12	968	29	917	23	681	15	209	6	23	2
Ratio (Winter–Spring/Summer–Fall)	1.13		1.35		1.27		0.99		0.74		0.56

TABLE 8 Variation of infiltrated outdoor particle number concentration (cm^{− 3}) by size category and by day of week

Weekdays	10–18 nm	SE	18–50 nm	SE	50–100 nm	SE	100–200 nm	SE	200–450 nm	SE	450–950 nm	SE	N (10–18 nm)	N (18–450 nm)	N (450– 950 nm)
Sunday	278	3	1148	7	1083	6	708	4	195	1	20	0.5	18984	28081	9215
Monday	374	3	1180	6	998	5	633	3	172	1	17	0.3	20419	30932	10653
Tuesday	343	3	1187	7	1043	5	624	3	170	1	19	0.4	19922	31041	11033
Wednesday	361	3	1151	6	1008	5	652	3	172	1	16	0.3	20681	31241	10395
Thursday	348	3	1153	6	1059	5	710	3	185	1	18	0.4	21628	32254	10803
Friday	336	3	1102	6	1082	5	694	3	174	1	15	0.2	20342	30297	10213
Saturday	318	3	1215	7	1131	5	743	4	193	1	20	0.3	20498	29258	9236

FIG. 8 Diurnal variation, no indoor sources. The increase observed at dinnertime (6–8 PM) may be partly due to difficulty in detecting minor peaks due to cooking.

FIG. 9 Diurnal variation, total particles (< 950 nm). When indoor sources are active, the mean particle concentration indoors is 6–10 times that due to infiltration of outdoor particles, with the main contribution coming during dinnertime cooking.

FIG. 10 Ultrafine particle concentration time course due to boiling water for tea and toasting bread (N = 245 events). Error bars are standard errors.

FIG. 11 Particle concentrations during and after baking a potato in a gas oven for 45 minutes and broiling fish in the oven for 8 minutes. (N = 66 events).

FIG. 12 Particle concentrations during and after deep-frying tortillas in peanut oil and then baking them with cheese and beans in an oven for 8 minutes. (N = 74 events).

TABLE 9 Size-resolved peak number and volume concentrations and estimated source strengths for common cooking events

	Tea & toast (N = 243)				Tortillas (N = 74)				Broiled fish (N = 64)
	Concentrations		Source strengths		Concentrations		Source strengths		Concentrations		Source strengths
Size	Number	Volume		Mass	Number	Volume		Mass	Number	Volume		Mass
(nm)	(cm ^−3)	(μ m/cm)^3	Number	(mg)	(cm^−3)	(μ m/cm)^3	Number	(mg)	(cm^−3)	(μ m/cm)^3	Number	(mg)
10–18	5360	0.01	2.06E+12	0.00	5259	0.01	2.02E+12	0.0	8347	0.01	3.21E+12	0.00
SE	382	0.00	1.47E+11	0.00	990	0.00	3.81E+11	0.0	1234	0.00	4.75E+11	0.00
18–50	5350	0.08	2.06E+12	0.03	38811	0.55	1.49E+13	0.2	40478	0.57	1.56E+13	0.22
SE	273	0.00	1.05E+11	0.00	3474	0.05	1.34E+12	0.0	4398	0.06	1.69E+12	0.02
50–100	1508	0.28	5.81E+11	0.11	41148	7.61	1.58E+13	2.9	20610	3.81	7.93E+12	1.47
SE	101	0.02	3.88E+10	0.01	3311	0.61	1.27E+12	0.2	3423	0.63	1.32E+12	0.24
100–200	616	0.91	2.37E+11	0.35	15291	22.63	5.89E+12	8.7	3643	5.39	1.40E+12	2.08
SE	27	0.04	1.05E+10	0.02	1449	2.14	5.58E+11	0.8	1005	1.49	3.87E+11	0.57
200–450	117	1.66	4.51E+10	0.64	1500	21.20	5.77E+11	8.2	225	3.18	8.66E+10	1.22
SE	6	0.08	2.17E+09	0.03	158	2.23	6.07E+10	0.9	34	0.48	1.32E+10	0.19
Total	12978	2.97	5.00E+12	1.14	102008	52.00	3.93E+13	20.0	73303	12.97	2.82E+13	4.99
SE	906	1.80	3.49E+11	0.69	9382	5.04	3.61E+12	1.9	10094	3	3.89E+12	1.03