The Indiana Air Pollution Control Board has passed a new rule—to take effect
on Wednesday, May 18—regulating the use of outdoor hydronic heaters (OHHs)
in the State of Indiana, the Indiana Department of Environmental Management
(IDEM) said on Wednesday.
That rule will restrict sales of future heaters to qualified units and
places restrictions on existing units close to neighbors’ buildings.
Outdoor hydronic heaters, also known as outdoor wood boilers or outdoor wood
furnaces, provide heat and hot water to homes, barns. and small businesses
by using wood to heat water.
“Traditionally used in rural or remote areas, OHH units are being installed
in more populated areas due to increases in petroleum and electric heating
bills,” IDEM said. “The smoke from these units can affect neighbors,
particularly when best management practices are not being used by the
The rulemaking process began over six years ago after IDEM received an
increasing number of complaints regarding OHH units. Development of the rule
was delayed several times as state and federal regulators researched the
impact of OHH emissions on human health and the environment.
Highlights of the new rule:
•All units are only allowed to burn clean wood or other approved fuels.
•Newly-installed OHH units must pass the U.S. EPA’s Phase II emission
•Non-Phase II units within 150 feet of occupied buildings on neighboring
property must have stack heights that are five feet above the peak of the
occupied building (stack height limited to 22 feet).
•Non-Phase II units within 300 feet of occupied buildings on neighboring
property are not allowed to operate from May 1 through September 30.
IDEM created a fact sheet about the rule. The fact sheet and other
information about OHHs can be found at
The agency is reaching out to owners of OHH units affected by the rule.
“A large number of comments from the public and regulated community also
affected the rulemaking,” IDEM said. “The agency received comments from over
1,000 citizens and businesses while considering the rule. Each type of
comment required a response before rulemaking could proceed.”
“We received more comments on this rule than we have on any other single
topic,” IDEM Commissioner Thomas Easterly said. “Getting the public to
participate throughout the process helped IDEM and the air board understand
how Hoosiers and our environment are being affected by these heaters. The
comments helped IDEM write a rule that would protect human health and the
environment while addressing public concerns. We also made a conscious
effort to not put undue restrictions on the people who operate their heaters
in a responsible manner.”