Influence of attached garages on indoor voc concentrations in anchorage homes
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Influence of Attached Garages on Indoor VOC Concentrations in Anchorage Homes. Stephen S. Morris, P.E. Municipality of Anchorage Department of Health and Human Services. Acknowledgements. Anne Schlapia, Matt Stichick and Larry Taylor – MOA DHHS John Freeman, Phil Kaluza, Ginny Moore – ABSN

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Influence of Attached Garages on Indoor VOC Concentrations in Anchorage Homes

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Influence of attached garages on indoor voc concentrations in anchorage homes

Influence of Attached Garages on Indoor VOC Concentrations in Anchorage Homes

Stephen S. Morris, P.E.

Municipality of Anchorage

Department of Health and Human Services


Acknowledgements

Acknowledgements

Anne Schlapia, Matt Stichick and Larry Taylor – MOA DHHS

John Freeman, Phil Kaluza, Ginny Moore – ABSN

Sally Liu, Tim Gould, Dave Hardie and Timothy Ting University of Washington


Background

Background


Influence of attached garages on indoor voc concentrations in anchorage homes

A previous Anchorage study sparked interest in a further investigation of the influence of attached garages on air quality inside Anchorage homes.


Influence of attached garages on indoor voc concentrations in anchorage homes

Architectural, Behavioral, and Environmental Factors Associated with Indoor VOCs in Anchorage Homes (1995)

  • Sampled 137 homes for BETX between December 1994 and February 1996

  • Summa canisters deployed in living space of homes for 24 hours

  • Documented architectural, behavioral and environmental characteristics of each home sampled


Influence of attached garages on indoor voc concentrations in anchorage homes

The most important factor influencing [benzene] and other BTEX compounds was the presence of an attached garage.

  • Cigarette smoking was not an important factor in determining benzene concentration in living space of the home.

  • The presence of an attached garage was the single most important variable associated with elevated benzene inside the home.


Influence of attached garages on indoor voc concentrations in anchorage homes

Comparison of Mean Benzene Concentrations in Single Family Homes

1994-1996 Anchorage Study

20.0

18.0

18.0

16.0

14.0

12.0

[benzene] ppb

10.0

8.0

6.8

6.0

3.2

4.0

2.0

0.0

garage

garage

no attached

with parked cars

w/o parked cars

garage

N = 46

N = 16

N = 14


Influence of attached garages on indoor voc concentrations in anchorage homes

Data suggested that attached garages increase in-home exposure to benzene five-fold. Incremental increase in lifetime exposure cancer risk was approximately 1 in 6,000.


Benzene content 3 9 and volatility of alaska gasoline is higher than most of the u s

Benzene content (3.9%) and volatility of Alaska gasoline is higher than most of the U.S.


We wanted to explore the mechanisms responsible for elevated benzene in homes with attached garages

We wanted to explore the mechanisms responsible for elevated benzene in homes with attached garages.


Study objectives

Study Objectives

  • Measure VOC concentrations in a representative sample of 50 Anchorage homes with attached garages to assess personal exposures.

  • Measure garage to house air infiltration rates. Determine architectural / mechanical factors affecting the amount of air entering house from the garage.

  • Identify possible strategies for reducing in-home VOC exposures through modification of architectural features, mechanical systems and/or modification of personal behaviors.


Influence of attached garages on indoor voc concentrations in anchorage homes

  • How much garage air infiltrates into the home and what are the responsible mechanisms?

  • How high are benzene and other VOCs inside the garage and what sources are responsible?


Influence of attached garages on indoor voc concentrations in anchorage homes

We narrowed study scope to include non-smoking, detached single familyhomes with attached garages only.

  • Simplified analysis of air exchange rates.

  • Eliminated other possible confounding variables.

  • Confined sampling to winter season when previous study showed VOC concentrations were highest.


House selection

House selection


A representative sample of anchorage homes was selected for sampling

A representative sample of Anchorage homes was selected for sampling.

  • Used Anchorage municipal property tax database to characterize housing stock by age and square footage.

  • Selected proportional number of houses in each sampling bin.


Influence of attached garages on indoor voc concentrations in anchorage homes

Age and size distribution of detached single family homes with attached garages in Anchorage.

Resultant sampling profile (50 home target)


Tracer gases were used to estimate air exchange rates between garage and house

Tracer gases were used to estimate air exchange rates between garage and house.


Influence of attached garages on indoor voc concentrations in anchorage homes

A PMCH tracer gas source emitter was deployed in each house and a PDCH source in each garage. The emission rate of each source was known.

PMCH

PDCH

house

garage


Influence of attached garages on indoor voc concentrations in anchorage homes

Capillary absorption tubes (CATs) were deployed in the house and garage to measure concentrations of PMCH and PDCH over a 24-hour period.

PMCH

C

A

T

PDCH

C

A

T


Influence of attached garages on indoor voc concentrations in anchorage homes

Mass balance approach was used to compute air exchange rates between garage and house, house and outside, and garage and outside.


Influence of attached garages on indoor voc concentrations in anchorage homes

QLG

QLA

PMCH

QGA

QGL

PDCH

Four simultaneous equations were developed to estimate 4 unknown flows from measured [PMCH] and [PDCH] and the known emission rates of the two tracer gases.

Simultaneous equations could be solved and flow rates QGL, QGA, QLG, and QLA could be computed for each house.


The proportion of air in the house coming from the garage could be easily derived

The proportion of air in the house coming from the garage could be easily derived.

Proportion of house air coming from garage =

QGL/(QGL + QAL)

QAL

PMCH

QGL

PDCH


Voc sampling methodology

VOC sampling methodology


Influence of attached garages on indoor voc concentrations in anchorage homes

  • ATD tubes were used to collect VOC samples in the house and garage.

  • Samplers were deployed in active living space in home, typically in living room.


Influence of attached garages on indoor voc concentrations in anchorage homes

Relationship Between Outdoor [CO] and [benzene]

7.0

6.0

5.0

4.0

ppb

Outdoor [benzene]

y = 1.7858x + 1.6288

2

3.0

R

= 0.5882

2.0

1.0

0.0

0.0

0.5

1.0

1.5

2.0

2.5

3.0

Outdoor [CO]

ppm

Ambient CO measurements were used to estimate outdoor concentrations of BTEX and butadiene.


Voc results

VOC results


Influence of attached garages on indoor voc concentrations in anchorage homes

Summary of In-house VOC Concentrations

N

mean

median

max

1,3-butadiene

46

0.73

0.44

6.26

benzene

45

7.60

5.16

35.49

carbon tetrachloride

46

0.08

0.09

0.13

chlorobenzene

46

0.14

0.09

0.62

ethylbenzene

46

2.51

1.65

9.34

methylene chloride

46

2.79

0.35

73.16

napthalene

46

0.14

0.08

1.20

o-xylene

46

2.98

2.15

11.21

toluene

46

18.89

12.91

81.73

trichloroethene

44

0.03

0.02

0.49

m,p-xylene

46

6.92

5.19

33.78


Influence of attached garages on indoor voc concentrations in anchorage homes

Distribution of Benzene Concentrations

Inside Homes with Attached Garages

25

22

20

15

12

Number of Homes

10

6

5

2

2

1

0

0

0 to

5 to

10 to

15 to

20 to

25 to

>30 ppb

5 ppb

10 ppb

15 ppb

20 ppb

25 ppb

30 ppb


Influence of attached garages on indoor voc concentrations in anchorage homes

For benzene and other BTEX compounds, mean concentrations in the house were approximately 5 times higher than outside.Garage concentrations were 10 to 15 times higher than outside.


Influence of attached garages on indoor voc concentrations in anchorage homes

Mean Benzene

30.00

26.08

25.00

20.00

ppb

15.00

10.00

7.60

5.00

1.66

0.00

House

Garage

Outdoor


Influence of attached garages on indoor voc concentrations in anchorage homes

Ethylbenzene

7.00

6.51

6.00

5.00

4.00

3.00

2.51

2.00

1.00

0.46

0.00

House

Garage

Outdoor

Toluene

70.00

61.35

60.00

50.00

40.00

30.00

18.89

20.00

10.00

5.42

0.00

House

Garage

Outdoor

o-Xylene

m,p- Xylene

9.00

25.00

8.50

21.82

8.00

20.00

7.00

6.00

15.00

5.00

4.00

10.00

2.98

3.00

6.92

2.00

5.00

0.72

1.00

1.44

0.00

0.00

House

Garage

Outdoor

House

Garage

Outdoor


Data analysis and discussion

Data Analysis and Discussion


Influence of attached garages on indoor voc concentrations in anchorage homes

Garage to house infiltration rates varied considerably among homes sampled.Homes with forced air furnaces in the garage had higher infiltration rates than homes with other heating configurations.


Influence of attached garages on indoor voc concentrations in anchorage homes

Comparison of Median Infiltration Rates

Proportion of House Air Originating from Garage

45%

40%

36.7%

35%

30%

25%

18.4%

20%

17.0%

15%

10%

5%

0%

Forced Air

Forced Air

Hydronic

Furnace

Furnace

N=11

in Garage

in House

N = 15

N = 5


Influence of attached garages on indoor voc concentrations in anchorage homes

Although the [CO] in many garages was high immediately after vehicle start-ups, exhaust emissions do not appear to be the primary source of VOCs in the garage.


Influence of attached garages on indoor voc concentrations in anchorage homes

House 30

50

House

40

Garage

30

Outside

[CO]

ppm

20

10

0

0

1

2

3

4

5

6

7

8

9

11

12

13

14

15

16

17

18

19

20

21

22

23

Hour of Day


Influence of attached garages on indoor voc concentrations in anchorage homes

CO vs benzene in garage

120

100

80

benzene (ppb)

60

2

R

= 0.2729

40

20

0

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

CO (ppm)


There was a stronger relationship between co and butadiene concentrations

There was a stronger relationship between CO and butadiene concentrations.


Influence of attached garages on indoor voc concentrations in anchorage homes

CO vs butadiene in garage

8

7

6

5

2

R

= 0.4111

butadiene (ppb)

4

3

2

1

0

0.00

2.00

4.00

6.00

8.00

10.00

12.00

14.00

16.00

18.00

CO (ppm)


The data do not show a significant association between the benzene level in the garage and

The data do not show a significant association between the benzene level in the garage and:

  • The number of vehicles parked in the garage;

  • The age of the vehicles in the garage; or

  • The number of trips originating from the garage.


Evaporative emissions may be a more important source than exhaust emissions

Evaporative emissions may be a more important source than exhaust emissions.


Influence of attached garages on indoor voc concentrations in anchorage homes

Comparison of Benzene Concentration in the Garage

35.0

32.3

30.0

25.0

20.0

median [benzene]

ppb

15.0

10.0

7.6

5.0

0.0

Garage Used

Garage Not Used

for Gasoline

for Gasoline

Equipment Storage

Equipment Storage

N = 23

N = 8


Influence of attached garages on indoor voc concentrations in anchorage homes

Having an elevated level of benzene in the garage was a good indicator that benzene levels in the house would also be high.


Influence of attached garages on indoor voc concentrations in anchorage homes

Garage Benzene vs. House Benzene

40

35

30

25

measured benzene in house (ppb)

20

y = 0.2789x + 0.4748

2

R

= 0.7291

15

10

5

0

0

20

40

60

80

100

120

measured benzene in garage


Influence of attached garages on indoor voc concentrations in anchorage homes

The benzene concentration in the house could be precisely predicted from the garage concentration if the air exchange rate between the garage and house was known.


Influence of attached garages on indoor voc concentrations in anchorage homes

[benzeneA]

QAL

?

PMCH

[benzeneL]

[benzeneG]

QGL

PDCH

[benzeneL] =

[benzeneA] x QAL/(QGL + QAL) + [benzeneG] x QGL/(QAL + QGL)


Influence of attached garages on indoor voc concentrations in anchorage homes

Computed vs. Measured House Benzene

40

35

30

25

y = 0.9224x +0.6102

2

R

= 0.9563

computed benzene in house (ppb)

20

15

10

5

0

0

5

10

15

20

25

30

35

40

measured benzene in house


Influence of attached garages on indoor voc concentrations in anchorage homes

The “average” Anchorage house….

- benzene concentration is 6 times higher than outside

- 27% of air in the house comes from garage

- over 90% of benzene in house comes from the garage

Outside air

[benzene] = 1.4 ppb

house

garage

[benzene] = 8.8 ppb

73% of air from outside

27% of air from garage

[benzene] = 29.8 ppb


Btex concentrations dropped considerably between 1994 96 study and 2003 2004 study

Comparison of In-home BTEX Concentrations

1994-94 study vs. 2003-2004 study

40.0

35.0

30.0

25.0

20.0

ppb

15.0

10.0

5.0

0.0

Benzene

Toluene

Ethylbenzene

m,p-Xylene

o-Xylene

1994-96 Study

2003-2004 Study

BTEX concentrations dropped considerably between 1994-96 study and 2003-2004 study


Phase 2 evaluation of mitigation strategies

Phase 2 – Evaluation of Mitigation Strategies


Candidate strategies

Candidate Strategies

  • Remove gasoline-fueled equipment from garage.

  • Modify forced air systems placed in garages to reduce air infiltration

  • Ventilate garage to reduce VOC concentrations

  • Lower benzene content in gasoline


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