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Outdoor Hydronic Heaters


Picture Source: Hearth, Patio and Barbecue Association (HPBA)

Outdoor hydronic heaters (also referred to as outdoor wood boilers or outdoor wood furnaces) are primarily used to heat homes or businesses; however, they also may be used to heat swimming pools and hot tubs. Indoor wood stoves and fireplaces are not considered outdoor hydronic heaters. To protect the air Hoosiers breathe, Indiana has adopted state rules concerning the purchase and use of outdoor hydronic heaters, joining other states that have adopted similar rules. Emissions from an outdoor hydronic heater can cause air pollution problems when the unit is not sited, installed, or operated properly.

How the Rule Affects Dealers, Sellers, and Buyers

The Outdoor Hydronic Heater rule at 326 IAC 4-3 establishes emission limits for new outdoor hydronic heaters. In addition, fuel use restriction, stack height requirements, and a limited summertime operating ban has been adopted for existing units. Sellers and dealers must provide a copy of the rule to buyers, and the buyer must sign a notice confirming receipt of the rule. The seller or dealer must send the signed notice to IDEM within 7 days of delivering the unit to the buyer or lessee. Dealers may use the Notice to Buyer (State Form 53597, available on the IDEM Forms page) to provide notice to IDEM.

Background Information

The Outdoor Hydronic Heater rule was adopted by the Indiana Air Pollution Control Board on March 2, 2011. The effective date of this rule is May 18, 2011. Note: the compliance date for the stack height requirement is November 30, 2011. The Indiana General Assembly website provides links to information including preliminary drafts and the final rule in the Indiana Register.

On April 2, 2020, U.S. EPA published the finalized amendments to the 2015 New Source Performance Standards (NSPS) for New Residential Wood Heaters, New Hydronic Heaters, and Forced-Air Furnaces (collectively referred to as wood heating devices). A fully searchable, U.S. EPA-certified Wood Heater Database provides information about heaters that are in compliance with the 2015 New Source Performance Standard (NSPS) for New Residential Wood Heaters, New Residential Hydronic Heaters, and Forced-Air Furnaces at 40 CFR Part 60 (Subpart AAA). More information about U.S. EPA’s regulation of outdoor hydronic heaters and other wood burning devices can be found on the Burn Wise site.

Local governments have authority to adopt ordinances that are more stringent or specific than state rules, and outdoor hydronic heaters may be regulated by local ordinances in some Indiana communities. IDEM’s Air Compliance and Enforcement Branch investigates air pollution complaints and works in coordination with local health officials to educate the public about reducing air pollution and nuisance smoke.

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