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

Affected: IC 13-17-3

Sec. 3. (a) Compliance with the emissions limitations specified in this rule shall be based on one or more of the following:

(1) For stack testing, the average of three (3) one-hour stack test runs.

(2) For permanent continuous emissions monitors, a twenty-four (24) hour daily heat input-weighted average.

(A) The twenty-four (24) hour daily heat input-weighted average NOx emission rate shall be determined based on the heat input-weighted average of the block hourly arithmetic average emission rates during each twenty-four (24) hour daily period from 12:00 a.m. to 12:00 a.m. the following day using continuous emissions monitor data. The block hourly heat input-weighted average emission rate shall be calculated for each one (1) hour period:

(i) starting with the period 12:00 a.m. to 1:00 a.m. and continuing through until the last period 11:00 p.m. to 12:00 a.m.; or

(ii) starting with the period 12:00 p.m. to 1:00 p.m. and continuing through the last period 11:00 a.m. to 12:00 p.m.

(B) The thirty (30) day rolling heat input-weighted average shall be the average of the twenty-four (24) hour daily heat input-weighted NOx emission rate.

(3) For temporary continuous emissions monitors, a thirty (30) day heat input-weighted average emission rate based on the twenty-four (24) hour daily heat input-weighted averages.

(A) The twenty-four (24) hour daily heat input-weighted average NOx emission rate shall be based on the heat input-weighted average of the block hourly arithmetic average emission rates during each twenty-four (24) hour daily period from 12:00 a.m. to 12:00 a.m. the following day using continuous emissions monitor data. The block hourly heat input-weighted average emission rate shall be calculated for each one (1) hour period:

(i) starting with the period 12:00 a.m. to 1:00 a.m. and continuing through until the last period 11:00 p.m. to 12:00 a.m.; or

(ii) starting with the period 12:00 p.m. to 1:00 p.m. and continuing through the last period 11:00 a.m. to 12:00 p.m.

(4) For permanent continuous emissions monitors, a daily, twenty-four (24) hour arithmetic average of all the block hourly mass emission rates, in pounds per hour, or concentrations, in parts per million by volume, during each calendar day.

(A) The block hourly mass emission rate or concentration shall be calculated for each one-hour period starting with:

(i) period 12:00 a.m. to 1:00 a.m. and continuing through until the last period 11:00 p.m. to 12:00 a.m.; or

(ii) starting with the period 12:00 p.m. to 1:00 p.m. and continuing through the last period 11:00 a.m. to 12:00 p.m.

(b) Compliance with a twelve (12) consecutive month limitation shall be determined at the end of each month.

(c) The owner or operator of a blast furnace gas boiler subject to tune-up requirements specified in this rule shall perform a tune-up of any unit no later than thirty (30) days after determining that the unit burned less than ninety percent (90%) blast furnace gas in a twelve (12) consecutive month period. If a unit has a continuous oxygen trim system and had a tune-up within three (3) years before a twelve (12) consecutive month period during which the unit burned ninety percent (90%) or more blast furnace gas by volume, the owner or operator must perform a subsequent tune-up no later than:

(1) thirty (30) days after determining that the unit burned less than ninety percent (90%) blast furnace gas by volume in a twelve (12) consecutive month period; or

(2) five (5) years after the previous tune-up.

(Air Pollution Control Division; 326 IAC 10-7-3; filed Oct 27, 2025, 10:54 a.m.: 20251126-IR-326250204FRA)