Published February 21, 2010 07:10 pm – The deadline is fast approaching for comments to be postmarked, faxed or hand delivered to the Indiana Department of Environmental Management (IDEM) regarding new limits on outdoor hydronic heaters.
Wood Stove Discussion Becoming Heated
Pollution Potential A Cause For IDEM Concern
Greensburg Daily News
Editor’s Note: This is the second of a two-part series examining pending rule changes for outdoor hydronic heaters – woodstoves used to heat water that warms homes and other buildings. This part focuses upon the inspiration for this regulation. Comments on this regulation will be accepted until the Monday deadline.
The deadline is fast approaching for comments to be postmarked, faxed or hand delivered to the Indiana Department of Environmental Management (IDEM) regarding new limits on outdoor hydronic heaters.
The Outdoor Hydronic Heater Model Regulation was developed and released by Northeastern States for Coordinated Air Use Management (NESCAUM), with technical and financial assistance from the EPA. IDEM has reviewed the model rule and believes that it can be tailored to address concerns about particulate matter emissions from outdoor hydronic heaters through the implementation of emission standards for new units and establishment of operational standards for existing units. The draft rule language proposes an emission limit based on the Phase 2 limit since this rulemaking will not be effective before March 31, 2010, the compliance date in the NESCAUM rule for Phase 2. This Second Notice of Comment Period proposes draft rule language adapted from the provisions contained in the model rule. Since IDEM’s proposed program relies on the EPA certification program, the applicability of the rule is limited to units designed for a thermal output of less than 350,000 British thermal units per hour (Btu/hr).
Several factors cause smoke to be an issue with outdoor hydronic heaters that citizens have complained about to IDEM, according to the organization. Larger capacity, low stack heights, design differences, operating conditions and lower operating temperatures cause more intense smoking and smoldering conditions nearer to ground level than with other wood-burning devices. Stack heights on outdoor hydronic heaters are typically in the range of eight to 10 feet above ground level. Chimneys on homes are almost always above the roof line and are typically 20 to 30 feet above ground level. The lower stack heights on the heater decrease the opportunity for wood smoke to disperse in the surrounding air before affecting nearby individuals and residences at ground level.
The basic design of older outdoor hydronic heaters causes fuel to burn incompletely, or smolder, which can result in thick smoke and high particulate emissions. The firebox in many older outdoor hydronic heaters is surrounded by a water filled jacket. The fire in the combustion chamber heats the water, but at the same time that water surrounding the firebox cools temperatures in the combustion chamber. Cooler combustion temperatures result in incomplete combustion, causing the fire to smoke. Problems with smoke are aggravated if an outdoor wood boiler is not sited properly or not used following manufacturers recommendations.
Another design feature of older outdoor hydronic heaters which results in increased emissions is the way the unit cycles on and off. Unlike natural gas and oil furnaces, outdoor hydronic heaters are not designed to cut off the fuel supply when heat is no longer required. The units are designed to slow combustion by significantly reducing the air supply to the combustion chamber. This results in a slow burning, smoldering fire which causes creosote to form on the inside of the firebox. When heat is again required from the unit, the air flow is restored and the rekindled fire then burns the accumulated creosote, resulting in thick smoke and increased pollutant emissions.
Outdoor hydronic heaters are used not only to provide heat to residences, but also to provide hot water to heat a variety of structures, including barns and warehouses. Outdoor hydronic heaters are also used for domestic hot water needs, as well as to heat swimming pools and hot tubs. Such uses can lead to year round operation of the units. During warm weather conditions the heavy smoke from outdoor hydronic heaters can result in nuisance conditions for nearby residents exposed more directly to the smoke due to an increase in outdoor activities or the opening of windows of the neighboring residence. Temperature inversions cause smoke to stay close to the ground.
As a result of the aforementioned factors, outdoor hydronic heaters have much higher amounts of particulate matter emissions and affect neighboring properties and individuals more directly than other home heating devices. According to a 1998 U.S. EPA report summarizing research on the issue, particulate matter and polycyclic aromatic hydrocarbon (PAH) emissions are much higher for all wood burning appliances than for other home heating appliances, such as for oil or natural gas furnaces. Based on ambient air quality testing performed on a typical unit operating in the field, NESCAUM estimates that currently available outdoor hydronic heaters can produce at least twenty times the amount of particulate matter emissions as a EPA-certified indoor woodstove, and can emit as much particulate matter as 50 to 500 idling diesel trucks. Among wood burning appliances, outdoor hydronic heaters have the highest emissions of particulate matter and PAHs. PAHs are a toxic air pollutant. Pellet stoves have the lowest amounts of these pollutant emissions. According to a 2005 report issued by the New York State Office of the Attorney General, outdoor hydronic heater emissions of fine particulate matter range from 18 to 147 grams per hour. The 2005 report summarized data from the EPA emissions tests as well as manufacturer supplied emissions tests and found the average outdoor hydronic heater to emit 72 grams per hour.
Newly installed units must be certified to meet an emission limit. Existing units may not be operated outside the normal winter heating season unless they have been certified to meet the emission limit. Existing units that do not meet emission limit must have a permanent stack extending five feet higher than the peak of any roof structure located within 150 feet of the unit. All units must meet a 20 percent opacity limit and follow fuel use restrictions. Opacity is the measure of how much light is visible through smoke and is used as a visual test for the concentration of particulate matter emissions. Sellers of outdoor hydronic units must provide notice to buyers of operating restrictions and notify the department of the transaction.