Lessons learned from a woodstove changeout on the Nez Perce Reservation

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Abstract

A woodstove changeout program was conducted within 16 homes on the Nez Perce Reservation in Idaho to evaluate the effectiveness of a woodstove changeout in improving indoor air quality. PM2.5 samples were collected within the common area (rooms where the stoves were located) of the homes both before and after the installation of cleaner burning EPA-certified stoves. During the pre- and post-changeout sampling, indoor PM2.5 mass, Organic Carbon (OC), Elemental Carbon (EC), and chemical markers of woodsmoke (including levoglucosan) were measured.

Sampling results from this study showed that indoor air quality was improved in 10 of the 16 homes following the woodstove changeout and educational training program. Five homes had increased indoor PM2.5 concentrations following the changeout, while one home did not have final PM2.5 results for comparison. The median pre-changeout PM2.5 mass (as measured by TSI DustTraks) was 39.2 μg/m3, with a median post-changeout concentration of 19.0 μg/m3. This resulted in an overall 52% reduction in median indoor PM2.5, a 36% reduction in mean indoor PM2.5 and a 60% reduction in PM2.5 spikes when the old stoves were replaced with EPA-certified stoves. Another significant finding of the project was that targeted education and outreach is a critical component of the overall success of the program. Effective messaging to homeowners on proper use of their new stove is a necessary task of a woodstove changeout.

Research highlights

▶ Indoor air quality was improved in 10 of 16 homes following the woodstove changeout and training. ▶ There was an overall 52% reduction in median indoor PM2.5 and a 36% reduction in mean indoor PM2.5. ▶ Targeted education and outreach was a critical component of the overall success of the program.

Introduction

In several rural valley locations throughout the northern Rocky Mountains, the major source of wintertime ambient PM2.5 has been identified as woodsmoke from residential woodstoves (Ward et al., 2006, Ward and Lange, 2010). These findings are consistent with studies conducted in other areas of the U.S. (Fairley, 1990, Larson et al., 2004, Maykut et al., 2003, Schauer and Cass, 2000, Sheesley et al., 2007, Zheng et al., 2002), New Zealand (McGowan et al., 2002), and Europe (Caseiro et al., 2009, Gelencser et al., 2007; Puxbaum et al., 2007, Szidat et al., 2007) showing that wood burning is a major source of ambient PM2.5. In many of these communities, woodstoves also serve as the primary source of home heating throughout the cold winter months. The Consumer Product Safety Commission estimates that there are 8.9 million woodstoves in use in the U.S., and they are the most intensively used type of space heater with an average annual usage per heater of 2100 h (Air Quality Management Work Group (AQMWG), 2005, Zamula, 1989).

One strategy of reducing ambient emissions of residential woodsmoke PM2.5 is by changing out old woodstoves with new, cleaner-burning EPA-certified woodstoves. An EPA-certified woodstove is defined as a stove that has been independently tested by an accredited laboratory, and meets a PM emissions limit of 7.5 g/h for noncatalytic wood stoves and 4.1 g/h for catalytic wood stoves. While older uncertified stoves and fireplaces release 40 to 60 g of particulate matter per hour, new EPA-certified stoves typically produce only 2 to 5 g of particulate matter per hour.

It has previously been demonstrated that aggressive campaigns to replace or remove uncertified, or “dirty,” woodstoves can have a substantial impact on local air quality, reducing ambient emissions by 60 to 80% (Air Quality Management Work Group, 2005). The first community-wide changeout was conducted in Crested Butte, CO in 1989–1990 where 48% of the 406 uncertified stoves were replaced by newer units, and another 33% were removed or disabled. This resulted in a 60% reduction in particulate matter during the subsequent winter (Houck et al., 2005). In another study, nearly 1200 old polluting woodstoves (out of over 2000 total home heating appliances) were changed out with cleaner burning models in Libby, Montana from 2005 to 2007. As a result of this changeout, average winter PM2.5 mass was reduced by ~ 20%, and woodsmoke related PM2.5 was reduced by 28% (Ward et al., 2010).

Even though old woodstoves are considered significant sources of ambient PM2.5, they have also been shown to be significant sources of indoor PM2.5. In a 20-home study conducted in Libby, Montana, indoor PM2.5 samples were collected to evaluate the effectiveness of a woodstove changeout on the indoor environment. Results from this study showed that average PM2.5 concentrations and maximum PM2.5 concentrations were reduced by 71% and 76%, respectively (as measured by TSI DustTraks) when old stoves were replaced with EPA-certified stoves (Ward et al., 2008). The results from this study suggested that woodstove changeouts have perhaps a bigger impact on the indoor environment compared to the intended reductions in reducing ambient woodsmoke PM2.5 concentrations.

The goal of this project was to evaluate the effectiveness of a woodstove changeout on indoor air quality within homes on the Nez Perce Reservation in Idaho. In addition to the initial changeout, comprehensive education/outreach training was provided within the homes to ensure that the residents were using best-burn practices. In this manuscript, we present the methodologies used throughout the project, as well as the results of the air sampling program. In addition, we present a summary of our lessons learned, which may be of interest to those public health officials considering woodstove changeouts within their communities.

Section snippets

Materials and methods

Sixteen homes were recruited into the Nez Perce woodstove changeout program. To participate in the study, homes had to be non-smoking, occupied by a tribal member, have an asthmatic child between the ages of 6 and 17, and use an older model woodstoves as their primary source of heat. The Nez Perce Tribe's Environmental Restoration and Waste Management (ERWM) Air Quality Program recruited homes through a number of outreach methods. As homes had to meet specific qualifications, finding

Results

The goal of the sampling program was to collect as many samples as possible within the 16 homes both before and after the stove changeout in an effort to evaluate the potential improvement in indoor air quality. Some homes had only one 24-hour sample collected pre- and post changeout, while other homes had up to five 24-hour samples collected. Before final concentrations were calculated for PM2.5, OC/EC, and chemical markers of woodsmoke, each 24-hour sample run collected in each of the 16

Impact of education and outreach following the changeout

Following the installation of EPA-certified woodstoves, some of the homes had higher PM2.5 concentrations measured inside the homes after the changeout when compared to pre-changeout levels. After determining the causes of these elevated concentrations through a review of the datasheets/activity logs collected within these homes, ERWM staff worked with the homeowners to deliver additional training. As a result of this education/outreach effort, PM2.5 concentrations were lowered within four

Conclusions

Over a three winter period (winters of 2006/2007, 2007/2008, and 2008/2009), a woodstove changeout program was conducted within 16 homes on the Nez Perce Reservation in Idaho. During each sampling event, continuous PM2.5 mass, OC, EC, and chemical markers of woodsmoke were measured to evaluate the impact of the woodstove changeout on the indoor environment. In addition, this afforded the opportunity to evaluate different outreach/education strategies in achieving optimal burn practices.

Sampling

Acknowledgements

The authors would like to thank the homeowners for participating in the study. Primary funding for this project was provided by the U.S. EPA Region 10. Additional funding was provided by NIH COBRE grant P20 RR017670 from NCRR.

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