Authority: IC 13-14-8-1; IC 13-14-9; IC 13-17-3-4

Affected: IC 13-11-2; IC 13-17-3

Sec. 2. The following definitions, and the definitions found in IC 13-11-2 and 326 IAC 1-2, apply to this rule:

(1) "Affected source" means any stationary source that meets the applicability requirements as specified in 326 IAC 10-7-1.

(2) "Affected facility" means any emission unit that meets the applicability requirements as specified in section 1 of this rule and is not exempt under section 7 of this rule.

(3) "Auxiliary boiler" means either a boiler that produces steam and operates at a capacity factor of less than ten per cent (10%) or a boiler at a nuclear electrical generating facility that produces steam for the facility during either emergency periods or atypical extended periods of nuclear plant outage.

(4) "British thermal unit" or "Btu" means the amount of heat needed to raise one (1) pound of water one degree Fahrenheit.

(5) "Capacity factor" means either the ratio of gross actual output to the gross rated output or the ratio of actual heat input to potential heat input for the calendar year, expressed as a percentage.

(6) "Cell burner" means burner cells that consist of two or three circular burners combined into a vertically oriented assembly that creates a compact, intense flame.

(7) "Diesel fuel" means a low sulfur fuel oil of grades 1-D or 2-D, as defined by ASTM D975, "Standard Specification for Diesel Fuel Oils"*.

(8) "Distillate oil" means fuel oil that complies with the specifications for fuel oil number one or two, as defined by ASTM D396, "Standard Specification for Fuel Oils"*.

(9) "Engine testing operation" means the activities, or the apparatus used in conducting testing of an internal combustion engine for the purpose of quality assurance or quality control in the manufacturing process of the engine, or for evaluating the pollutant emissions emitted by the engine.

(10) "Gaseous fuels" means natural gas, blast furnace gas, coke oven gas or refinery fuel gas.

(11) "g per kW-hr" or "g/kW-hour" means grams per kilowatt-hour.

(12) "g per hp-hr" or "g/hp-hour" means grams per horsepower-hour.

(13) "Hp" means horsepower.

(14) "Industrial boiler" means a steam generating unit that generates steam to supply power or heat to an industrial, institutional, or commercial operation. This term does not include boilers that serve electrical generating units and cogeneration facilities.

(15) "Internal combustion engine" means any engine in which power, produced by heat or pressure developed in the engine cylinder by burning a mixture of air and fuel, including diesel fuel, is subsequently converted to mechanical work by means of one (1) or more pistons.

(16) "kW" means kilowatt.

(17) "Lb per mmBtu" or "lb/mmBtu" means pound per million British thermal units.

(18) "Lb per MW-hr" or "lb/MW-hour" means pound per megawatt-hour.

(19) "Large boiler" means an industrial boiler with a maximum heat input capacity greater than one hundred (100) mmBtu/hr and equal to or less than two hundred fifty (250) mmBtu/hr.

(20) "Low-NOx burner" means a burner designed to reduce flame turbulence by the mixing of fuel and air and by establishing fuel-rich zones for initial combustion, thereby reducing the formation of NOx.

(21) "Mid-size boiler" means an industrial boiler with a maximum heat input capacity greater than fifty (50) mmBtu/hr and equal to or less than one hundred (100) mmBtu/hr.

(22) "MmBtu/hr" means million British thermal units per hour.

(23) "Municipal waste combustor" means any device that combusts any solid, liquid, or gasified municipal waste.

(24) "Natural gas" means a naturally occurring mixture of hydrocarbon and non-hydrocarbon gases found in geologic formations beneath the earth's surface, of which the principal constituent is methane.

(25) "ng/J" means nanogram per joule.

(26) "Nitrogen oxides" or "NOx" means all nitrogen oxides which are determined to be ozone precursors, including, but not limited to, nitrogen oxide and nitrogen dioxide, but excluding nitrous oxide, collectively expressed as nitrogen dioxide.

(27) "O₂" means Oxygen.

(28) "Oil" means crude oil or petroleum, or a liquid fuel derived from crude oil or petroleum, including distillate oil and residual oil.

(29) "Operating day" is defined as any calendar day with twelve (12) or more hours during which wind is being added to a furnace and the top pressure of the furnace is greater than five (5) pounds per square inch gauge.

(30) "Potential to emit" means the maximum capacity of a facility or stationary source to emit NOx under its physical and operational design. Any physical or operational limitation on the capacity of the facility to emit NOx, including air pollution control equipment and restrictions on hours of operation or on the type or amount of material combusted, stored or processed, is treated as part of its design if the limitation or the effect it would have on emissions is federally enforceable.

(31) "Ppm" means parts per million.

(32) "RACT" or "reasonably available control technology" means the lowest emissions limitation that a particular facility is capable of meeting by the application of control technology that is reasonably available considering technological and economic feasibility.

(33) "Reheat furnace" means a furnace in which metal ingots, billets, slabs, beams, blooms and other similar products are heated to the temperature needed for hot-working.

(34) "Research and development facility" means a research or laboratory facility the primary purpose of which is to conduct research and development into new processes and products, that is operated under the close supervision of technically trained personnel, and that is not engaged in the manufacture of products for sale or exchange for commercial profit, except in a de-minimis manner.

(35) "Residual oil" means crude oil, fuel oil that does not comply with the specifications under the definition of "distillate oil," and all fuel oil numbers four, five, or six, as defined by ASTM D396, "Standard Specification for Fuel Oils"*.

(36) "Small boiler" means an industrial boiler with a maximum heat input capacity greater than twenty (20) mmBtu/hr and equal to or less than fifty (50) mmBtu/hr.

(37) "Space heating unit" means any fuel burning equipment that is used only for space heating purposes during the period from November first through March thirty-first or during other periods of cold weather conditions.

(38) "Stand-by fuel burning equipment" means any fuel burning equipment which is used only as a direct substitution for other fuel burning equipment for a limited period due to unpredictable breakdown or failure, or routine scheduled maintenance of such other fuel burning equipment or its associated air pollution control system. Stand-by fuel burning equipment includes engines that meet the definition of:

(A) emergency stationary reciprocating internal combustion engine (RICE) under 40 CFR Part 63, Subpart ZZZZ*; or

(B) emergency stationary internal combustion engine under:

(i) 40 CFR Part 60, Subpart IIII*; and

(ii) 40 CFR Part 60, Subpart JJJJ*.

(39) "Stationary combustion turbine" means any:

(A) simple cycle combustion turbine;

(B) regenerative cycle combustion turbine; or

(C) combustion turbine portion of a combined cycle steam or electric generating system;

that is not self-propelled, but which may be mounted on a vehicle for portability.

(40) "Stationary internal combustion engine" means any reciprocating internal combustion engine that is not self-propelled, but which may be mounted on a vehicle for portability.

(41) "Tune-up" means adjustments made to a burner or boiler in accordance with procedures supplied by the manufacturer (or approved specialist) to optimize the combustion efficiency.

(42) "Very large boiler" means an industrial boiler with a maximum heat input capacity greater than two hundred fifty (250) mmBtu/hr.

*These documents are incorporated by reference. Copies may be obtained from the Government Publishing Office, www.gpo.gov, or are available for review at the Indiana Department of Environmental Management, Office of Legal Counsel, Indiana Government Center North, 100 North Senate Avenue, Thirteenth Floor, Indianapolis, IN 46204.

(Air Pollution Control Division; 326 IAC 10-7-2; filed Oct 27, 2025, 10:54 a.m.: 20251126-IR-326250204FRA)