Authority: IC 13-14-8; IC 13-17-3-4; IC 13-17-3-11

Affected: IC 13-15; IC 13-17

Sec. 4. (a) Uncontrolled total annual mass emissions shall be determined by the following methods:

1. (1) Direct process vent emissions measurements taken prior to any release to the atmosphere, following any recovery device, prior to mixing with vents from other process trains or unrelated operations, and prior to any control device, provided the measurements conform with the requirements of measuring the mass flow rate of VOC incoming to the control device as set forth in section 5(f)(2), 5(f)(3)(A)(i), and 5(f)(3)(A)(ii) of this rule.

2. (2) Engineering estimates of the uncontrolled VOC emissions from a process vent or process vents, in the aggregate, within a batch process train, using either the potential or permitted number of batch cycles per year or total production as represented in the permit for the batch process train as follows:

   1. (A) Engineering estimates of the uncontrolled VOC emissions shall be based upon accepted chemical engineering principles, measurable process parameters, or physical or chemical laws and their properties. Examples of methods include, but are not limited to, the following:

      1. (i) Use of material balances based on process stoichiometry to estimate maximum VOC concentrations.
      2. (ii) Estimation of maximum flow rate based on physical equipment design, such as pump or blower capacities.
      3. (iii) Estimation of VOC concentrations based on saturation conditions.
   2. (B) All data, assumptions, and procedures used in any engineering estimate shall be documented.

(b) Average flow rate shall be determined by any of the following methods:

1. (1) Direct process vent flow rate measurements taken prior to any release to the atmosphere, following any recovery device, prior to mixing with vents from other process trains or unrelated operations, and prior to any control device, provided the measurements conform with the requirements of measuring incoming volumetric flow rate set forth in section 5(f)(2) of this rule.

2. (2) Average flow rate for a unit operation having multiple emission events or batch process trains shall be the weighted average flow rate, calculated as follows:

   Where:	WAF	=	actual weighted average flow rate for a unit operation or batch process train.
   	AFRi	=	average flow rate of emission event i.
   	ADEi	=	annual duration of emission event i.
   	i	=	subscript denoting a specific emission event.
   	n	=	number of emission events.

3. (3) Engineering estimates calculated in accordance with the requirements in subsection (a)(2).

(c) For purposes of determining the average flow rate for steam vacuuming systems, the steam flow shall be included in the average flow rate calculation.

(Air Pollution Control Division; 326 IAC 8-19-4; filed Nov 3, 2009, 3:32 p.m.: 20091202-IR-326090222FRA; readopted filed Oct 18, 2024, 2:09 p.m.: 20241113-IR-326230809RFA)