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Basic Information
A typical outdoor wood-fired hydronic heater (OWHH, also known as an "Outdoor Wood Heater," "Outdoor Wood Boiler," or "Outdoor Wood Furnace") burns wood to heat water that is piped underground to a nearby structure (usually a home) resulting in heat for the building. An OWHH resembles a small shed with a smokestack, typically located on the outside of the building to be heated. Most OWHHs are sold for use in rural, cold climate areas where wood is readily available; however, OWHHs can be found throughout the United States.
Source: Hearth, Patio and Barbecue Association (HPBA)
Outdoor wood-fired hydronic heaters can be substantially dirtier and less efficient than most other home heating technologies. With their smoldering fires and short smokestacks (usually no more than six to ten feet tall), OWHHs create heavy smoke and release it close to the ground, where it often lingers and exposes people in the area to nuisance conditions and health risks.
Although these units are designed to burn dry, seasoned wood, some people use them to burn green wood, which generates much more smoke. Others burn household trash or construction debris, which not only release harmful chemicals and pollution, but can be against state law.
Outdoor wood-fired hydronic heater emissions are a significant concern in many local areas. Numerous scientific studies report potentially serious adverse health effects from breathing smoke emitted by residential wood combustion. Residential wood smoke contains fine particles, which can affect both the lungs and the heart. In some areas, residential wood smoke can be a significant source of exposure to fine particle pollution.
Many local agencies have developed ordinances that will soon regulate outdoor wood-fired hydronic heaters. EPA worked with the Northeast States for Coordinated Air Use Management (NESCAUM) and others to develop a model rule that state and local agencies can use to regulate outdoor wood-fired hydronic heater emissions.
EPA also has initiated a voluntary program for manufacturers of OWHHs. EPA’s primary intent is to first encourage manufacturers to produce cleaner OWHH models. EPA also wants those who buy an OWHH to buy the cleanest models available, which are those that meet EPA performance verified levels. In addition, the program will focus on educating new and current OWHH users on the health effects of woodsmoke, what to look for when purchasing these units, and how to properly operate an OWHH.
This program encourages manufacturers to produce and sell cleaner, more efficient OWHHs that meet a certain performance level. To participate in the OWHH program, manufacturers commit their best efforts to develop cleaner models with the goal of distributing these units starting in April 2007.