Dirty Air from Outdoor Wood Boilers (OWBs) in Indiana

About Outdoor Wood Fired Boilers, OWB’s or Hydronic Heaters

OWB SmokeMore than 8,000 homes across Indiana heat their homes and water using an Outdoor Wood Boiler (OWBs), a technology that looks, from the outside, like a small metal shed with a smokestack 8 to 10 feet above ground level.




The basic design of outdoor wood boilers causes fuel to burn incompletely, or smolder, which results in thick smoke and potentially high particulate matter emissions.

The EPA estimates that most OWBs have only a 30 to 50 percent combustion efficiency .

OWB can be especially a problem if an OWB has a small smokestack height and/or a short distance from a neighboring property.

OWBs are supposed to be powered by dry wood, but unfortunately some users – with complete disregard for the health of their neighbors – burn treated lumber, painted wood, cardboard boxes, trash, dead animals, all of which can be especially damaging .
“The smoke drifts across property lines and can penetrate even closed nearby structures, due to the very small size of PM2.5.”

A recent study showed that 50 to 70 percent of outdoor wood smoke entered homes that were not burning wood .

Real Suffering, Especially for School Kids, the Elderly, and those with Respiratory Illnesses

“Some of the health effects reported…include awakening at night with coughing, headaches, inability to catch breath, continual sore throats, bronchitis and colds requiring children to stay home from school. In some cases the breathing difficulty has gone into asthma attacks requiring emergency-room treatment. Even episodes of short-term exposures to extreme levels of fine particulates from wood smoke and other sources, for periods as short as two hours, can produce significant adverse effects.”

–Public Health Toxicologist David Brown, Sc.D., an expert in wood smoke.

“In addition to the fine particulate matter, wood smoke contains a number of organic compounds that are potential or recognized carcinogens. Exposure over time may raise the risk not only of chronic lung disease but also of lung cancer. As well, wood smoke interferes with normal lung development in infants and children. It increases children’s risk of lower respiratory infections such as bronchitis and pneumonia. Wood smoke exposure can depress the immune system and damage the layer of cells in the lungs that protect and cleanse the airways.”

-Oncologist D. Barry Boyd, MD.

Other Struggles Facing Victims of OWB Wood Smoke
•    People boarding up their homes to try to keep out smoke.
•    Working class families spending money that could have been used to buy food or clothing are forced to buy expensive air filtration systems to protect their families from the plumes of smoke coming at them, 24 hours a day, 7 days a week.   One HEPA replacement filter can alone cost $90.

The Science: Public Health Dangers of OWBs or Hydronic Heaters
•    “Pollutants in the emissions from outdoor Hydronic heaters also include carbon monoxide, and volatile organic compounds, including air toxics such as formaldehyde, benzene, and a number of trace chemicals”
•    Operating year round, one OWB emits 1.55 tons/year of PM2.5.  That’s the same amount as 50 diesel trucks .
“An average outdoor Hydronic heater (OWB) emits 72 grams of particulate matter per hour and an indoor US EPA certified wood stove emits on average less than 6 grams of particulate matter per hour”
•    OWBs emit 5-40 times more cancer-causing particles than normal wood stoves .
•    OWBs emit 1000 times more cancer-causing particles than natural gas furnaces .
•    A house 120 feet from an OWF had over 8 times the levels of PM 2.5 as the houses not near an outdoor wood furnace, and 6 times the levels of the EPA air standards .

More Problems with OWBs or Hydronic Heaters
•    They can depress property values
•    Homeowners are legally required to disclose to potential buyers that the neighbor’s OWBs are potential hazards because of the wood smoke.
•    They can be very labor-intensive to operate and maintain.

The Current Situation
•    Some municipalities have moratoriums or bans on OWB’s or Hydronic Heaters:
◦    Cities (Indianapolis, Evansville, Greencastle, Michigan City, The City of LaPorte, Long Beach )
◦    Towns (Avilla, Batesville, Greendale, Lagootee, Petersburg, Rome City)
•    Indiana’s Outdoor Wood Boiler rule does pertain to both existing and new OWBs, but it still has serious gaps that continue to lead to harm.    The federal government’s new OWB rule only pertains to new OWBs.

How HEC is Responding

  • HEC has led coalitions that have successfully blocked anti-environmental legislation that may have foreclosed the possibility of amending Indiana’s weak Outdoor Wood Boiler policy.
  • HEC won a six year lawsuit that put an end to the suffering of people exposed to noxious outdoor wood boiler smoke – while setting legal precedent that will help safeguard other families
  • HEC and our Indiana public interest colleagues partnered with the American Lung Association of the Upper Midwest to launch an innovative program that incentivized the replacement of old OWBs with clean, renewable energy.   It is, to our knowledge, the first such program in the country.    Media interest in this innovative program has been significant, as seen by reports by WFYI, WFPL, Elkhart Truth, and more.