The House As a Chimney Combustion Gas Concentrations from Unvented Fireplaces
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The House as a Chimney Combustion Gas Concentrations from Unvented Fireplaces Jeffrey Gordon Building Research Council University of Illinois 1 HUD Healthy Homes 04 Grant • Investigate the concentration of combustion gases in houses using “vent- free” gas fireplaces. • Examine the factors that will impact the gas concentrations, on both the generation and dilution sides. 2 Unvented Gas Fireplaces • About 30 million sold in the U.S. since 1980 • Intended use – supplemental heat, not primary heat, and decorative ambiance • Sizing of unit emphasized (40,000 Btu max) • All combustion gases released into home • Popular for cost, ease of installation, efficiency 3 Bridging the Chasm Industry BS and Others “These things “What are you, are safe. nuts? This is No problem.” crazy” AGARD report Some anecdotal studies 4 Project Activities • Field Test 30 houses – combustion gas concentrations • Lab test new and used vent-free fireplaces • Modeling • Survey of Users Analyygsis grew with the richness of the dataset – decay rates, moisture analysis Will focus on the field tests today 5 Gas Concentrations of Concern • Carbon Dioxide (CO2) • Water Vapour (H2O) • CbCarbon Monox id(CO)ide (CO) •NOx, NO, and Nitrogen Dioxide (NO2) • Oxygen (O2) Did not study particulates or other minor gases 6 BRC Researchers • Paul Francisco, Co-PI • Jeff Gordon, Co-PI • Bill Rose, Instrument Guru and Scapegoat 7 Experimental Setup BllVlBall Valve Vacuum pump Desiccant chamber Rotameter CO2 CO Permeation drier NO2 Heater Ball Valve Vacuum gauge Rotameter 8 Instrument Cart • CO and CO2 - non- dispersive infrared analyzer •NOx, NO, NO2 – chemiluminescence analyzer •O2 – paramagnetic analyzer integral to the NOx analyzer • Pumps, rotameters, gau ges, dry ers, bells and whistles All instruments were calibrated at each house 9 HOBO Remote Sensors • Temp/RH •CO •Exterior Temp/RH CO2 10 Field Tests • Tested 30 homes using unvented gas fireplaces • Measurements every minute for 3-4 days • Indoor combustion gas concentrations: CO, CO2, NOx, NO, NO2, O2, H2O • Also measured temperatures (on/off times of fireplace and primary heating – furnace) 11 Housing Characteristics House Age House Size Blower Door Fireplace Age (Years) (ft2) (ACH50) (Years) Minimum 3 1195 5.6 0 (4 weeks) MdiMedian 34 1959 11. 4 4 Maximum 100 3000 26.3 15 All houses in Central Illinois. Usage patterns were equally variable. 12 Threshold Values Combustion Threshold Value Source Notes Product 250 ppb – 1 hr avg Health Canada NO2 No US standard 110 ppb - 1hravg1 hr avg WHO 9 ppm – 8 hr avg US EPA 9 ppm WHO CO 35 ppm – 1 hr avg US EPA 25 ppm WHO CO2 3500 ppm Health Canada “Long-term” avg O “Oxygen depleted 2 19.5% continuous NIOSH (depletion) environment” Also Dewpo in t > 60% RH ASHRAE 55-92 H2O 10 Co 13 What does the data look like? Case Study: House #18 One study of n = 30, but also 30 studies of n = 1 In this case: • One story ranch house • Retired couple • Infrequent fireplace usage – aabecembience 14 Temp F 200 100 120 140 160 180 20 40 60 80 0 1238 What doesthedatalook like?– 1421 min 156 1604 12/11 1747 1930 2113 2256 TtTili T 39 222 empera 405 548 731 914 12/12 1057 1240 1423 1606 Figure 1: Fireplace Use 1: Fireplace Figure 1749 79 min 1932 min t 2115 ure 2258 41 224 407 550 733 Ti 916 12/13 1059 me 1242 1425 74 min 1608 min 1751 li 1934 2117 ne 2300 43 226 exterior temp F temp exterior Furnace Room Fireplace 409 12/14 552 735 918 1101 15 ppm 1000 1500 2000 2500 3000 3500 4000 500 0 1238 1416 1554 12/11 1732 1910 935 ppm - average Test period 935 ppm 2048 Carbon DioxideTimeline 2226 4 142 320 458 636 814 952 12/12 1130 Canada - Health Long Term 3500 ppm 1308 4:Figure Concentration CO2 1446 1624 1802 1940 2118 2256 34 212 350 528 706 844 1022 12/13 1200 1338 1516 1654 1832 2010 2148 2326 104 242 420 12/14 558 736 914 1052 16 10 15 20 25 30 0 5 CO ppm 1238 1420 1602 12/11 1744 Carbon Monoxide Timeline 1926 2108 2250 32 214 8-hr standard9 ppm = EPA 356 538 720 902 1044 12/12 1226 Monoxide 1408 1550 Figure 2: CO Concentration 2: CO Figure 1732 1914 2056 2238 20 202 344 526 708 850 12/13 1032 1214 Timeline 1356 1538 1720 1902 2044 2226 8 150 332 8hour CO 1hour CO CO ppm 12/14 514 656 838 1020 17 NO2 ppm 0.1 0.2 0.3 0.4 0.5 060 0.7 0.8 . 6 0 1238 1415 1552 12/11 1729 Nitrogen Dioxide Timeline 1906 2043 Health Canada = 250 ppb 1 hr avg 2220 avg hour 1 ppb 110 = WHO 2357 Canada 134 311 448 = 625 250 802 ppb 939 12/12 1 1116 hr 1253 avg 1430 6:Concentration Figure NO2 Dioxide 1607 1744 1921 2058 2235 12 149 326 503 640 817 954 12/13 Timeline 1131 1308 1445 1622 1759 1936 2113 2250 27 204 341 NO2 1hour NO2 NO2 ppm 12/14 518 655 832 1009 1146 18 Dewpoint Temperature 55 50 12/11 45 40 F p Tem Timeline 35 12/12 Figure 7: DewPoint Temp 30 25 20 1238 mantel Dewpt F Nextrm Dewpt 1509 midrm Dewpt Condesation potential of double pane window @ 10 F outside 1740 12/13 2011 2242 113 344 615 846 1117 12/14 1348 1619 1850 2121 2352 223 Ti me 454 725 956 1227 1458 1729 2000 2231 102 333 604 835 1106 19 O2 % 19.25 19.75 20.25 20.75 19.5 20.5 20 21 19 1238 1416 1554 12/11 1732 1910 2048 2226 4 142 320 458 Oxygen Timeline 636 814 952 12/12 1130 1308 Concentration 5: Oxygen Figure 1446 O2 ThresholdNIOSH = 19.5% 1624 1802 1940 2118 2256 34 212 350 528 706 844 1022 12/13 1200 1338 1516 1654 1832 2010 2148 2326 104 242 420 12/14 558 736 914 1052 20 Vent-Free Field Tests Results CO CO2 NO2 O2 H2O FIELD TEST >35> 35 >9> 9 > 3500 > 250 >110> 110 SUMMARY ppm ppm ppm ppb ppb <19.5 DP > 1hr avg 8hr avg test avg 1hr avg 1hr avg % 10 Co Year 1 Count 0 2 0 7 11 0 4 Field Tests % 0.0% 13.3% 0.0% 46.7% 73.3% 0.0% 26.7% (n=15) Year 2 Count 04061313 Field Tests % 0.0% 26.7% 0.0% 40.0% 86.7% 6.7% 20.0% (n=15) All Count 0 6 0 13 24 1 7 Field Test % 00%0.0% 20. 0% 00%0.0% 43. 3% 80. 0% 33%3.3% 23. 3% (n=30) 21 N = 30 Conclusions • 20% of homes exceeded the 8-hour avg. threshold for CO, typicall y durin g extended use of the fireplace. Only one of these exceeded 10.1 ppm. None of the homes exceeded the 1-hour avg. threshold of 35 ppm. • Most problematic combustion product was NO2. 43% exceeded the 250 ppb threshold. 80% exceeded the 110 ppb threshold. • Humidityyp was not a problem in an y house. • Oxygen depletion was rare, and never triggered the oxygen depletion sensor. One house fell below the 19. 5% t hres ho ld. 22 N = 30 Conclusions • Primary vs. Secondary heating . This was an elusive distinction. Some occupants turned down the thermostat to the furnace. In many cases, proximity to fireplace overrode the furnace thermostat. Fireplace was often the prihtimary heat source. OhOne house use ditd it exclusively as primary, and had extremely high CO2 and NO2 levels • When the fireplace is operating it usually acts as primary – furnace does not operate 23 Gas Concentration Factors • Generation – Size (BTU/hr) of appliance – Duration of Use – High vs. low settings – Maintenance – Primary vs. Secondary heat source – Continuous vs. Cycling operation – Insulation – heat loss 24 Gas Concentration Factors • Dilution – Air change rate (blower door test) – House size, CAZ size – Ventilation provided at installation – Supplemental ventilation during operation (window use, door use) – Age of house 25 Conclusions: Correlations • Correlations. Based on single and multi- variable analysis, there was no specific house or fireplace characteristic that predicted the concentration of any of the combustion gases. • None of these factors had a statistically significant correlation to any gas concentration or accumulation rate • IdiIndicator o f many iflinfluences, too sma llfll of a dataset to extricate causality 26 Relationship between gases • All gas accumulation rates were highly correlated, EXCEPT for CO. • Suggests that all gases but CO are purely from basic combustion • CO has o ther con tr ibu tors 27 CO vs . NOx • Common belief: – Cooler flame leads to higher CO, lower NOx – Hotter flame leads to lower CO, higher NOx • Does not consider additional contributors tCOdto CO produc tion • Does not necessarily mean NO2 28 CO vs NO/NO2 Ratio 16 14 12 R2 = 0.4858 ee 10 8 -hour averag -hour 88 6 Max C0 C0 Max 4 2 0 0 5 10 15 20 25 30 35 40 45 50 NO2/NOx % 29 AFewNA Few N = 1Examples1 Examples • What about an old leaky house? • 26.3 ACH50 • 2ldfil2 year old fireplace • Constant cycling on thermostat 30 Temp F 100 120 140 160 180 20 40 60 80 0 1501 1701 1901 2/5 2101 2301 101 301 501 701 901 1101 2/6 1301 1501 1701 Figure 1: Fireplace Use 1:Fireplace Figure 1901 2101 2301 101 301 501 701 901 1101 2/7 1301 1501 1701 1901 2101 2301 101 Temp Exterior Room Temp Fireplace 301 Temp 2/8 501 701 901 31 10 9 2/5 8 7 6 EPA standard = 9 ppm 8-hr avg O ppm C 5 Fi 2 CO C t ti 2/6 gure 4 2 : CO 3 C oncen 2 tra ti ons 1 0 1501 1731 2/7 2001 2231 101 331 CO ppm 601 CO -1hr avera CO -8hr average 831 1101 g 2/8 e 1331 1601 1831 2101 2331 201 431 701 931 1201 1431 1701 1931 2201 31 301 531 801 32 CO2 ppm 4000 1000 1500 2000 2500 3000 3500 500 0 1501 1701 1901 2/5 2101 3500 ppm Long Term - Health Canada -Health 3500 ppm Term Long 2301 101 301 501 701 901 1101 2/6 1301 Figure 3: CO2 Concentrations 1501 1701 3: 1901 CO2 2101 Concentrations 2301 101 301 501 701 901 1153 ppm Test Period Average Period Test ppm 1153 1101 2/7 1301 1501 CO2 ppm Hariba CO2 exterior 1701 exterior 1901 2101 2301 101 301 2/8 501 701 33 901 House Example #3 – Site 26 • 12.