(c) The overall removal efficiency of an air cleaning device used as a control strategy must be determined, for every surface coating formulation, on a solids as applied basis using Equation 2 unless a 90 percent or greater overall removal efficiency is achieved by the air cleaning device. The air cleaning device must be designed and operated to provide, at a minimum, an overall removal efficiency of either 90 percent or as determined by Equation 2.

Equation 2

​

where:

η is the overall removal efficiency

(VOC)_a is the VOC content of an as applied coating, expressed as pounds of VOC per gallon of coating minus water and excluded compounds.

(V_n)_c is the volumetric fraction of solids, expressed as gallon of solids per gallon of coating minus water and excluded compounds, in a compliant coating expressed as:

Equation 3

(V_n)_c = 1 − (V_v)_c

(V_v)_c is the volumetric fraction of VOC, expressed as gallon of VOC per gallon of coating minus water and excluded compounds, in a compliant coating expressed as:

Equation 4

​

(V_n)_a is the volumetric fraction of solids, expressed as gallon of solids per gallon of coating minus water and excluded compounds, in an as applied coating expressed as:

Equation 5

(V_n)_a = 1 − (V_v)_a

(V_v)_a is the volumetric fraction of VOC, expressed as gallon of VOC per gallon of coating minus water and excluded compounds, in an as applied coating expressed as:

Equation 6

​

d_voc is the density of VOC as applied, i.e., total volatiles minus water and excluded compounds, in pounds of VOC per gallon of VOC.

(d) An owner or operator of a coating line which utilizes a coating system as a control strategy, which control strategy may also employ a control device, must comply with the following provisions:

1. (1) the coating system must be approved by the department prior to the use of the coating system in the manufacture of a product for sale;
2. (2) coatings which are applied manually by handheld spray guns cannot be utilized in a coating system;

3. (3) the emission differential (ED) for a coating system must be determined using equation 7 below. The ED for the coating system is the sum of the individual ED values calculated for every coating used in the coating system. The ED calculation requirement is to be performed each time the series of coatings in a coating system is changed. The coating system ED must be less than or equal to zero before the coating system may be operated. ​ ​

   Equation 7

   ​

   where:

   V is the actual coating volume used, minus water and excluded compounds, in gallons.

   η is the overall removal efficiency, expressed as:

   Equation 8

   ​

   where:

   η_c is the percent CE, as determined by section 228-1.6(d)(2) of this Subpart.

   η_d is the percent destruction and/or removal efficiency, as determined by section 228-1.6(d)(1) of this Subpart.

   η = 0, for coating systems without a control device and capture system.

   d_VOC = 7.36 pounds of VOC per gallon of VOC when (VOC)_a = 0 and (V_n)_a=1

   When section 228-1.6(d)(1) of this Subpart applies, η is the VOC solvent recovery fraction.

   All other terms are defined in subdivision (c) of this section.

4. (4) the ED figures for the individual coating used in the coating system must be calculated on an instantaneous basis. There is no averaging period for individual coatings which are part of a coating system; and

5. (5) the method or instrument by which the owner or operator will measure or calculate the volume of coating applied must be approved by the department.

   (e) Process specific RACT demonstrations.

6. (1) The department may allow surface coating processes to operate with a lesser degree of control than is required by this section provided that a process specific reasonably available control technology (RACT) demonstration has been made to the satisfaction of the department. Such process specific RACT demonstrations must be submitted to the administrator for approval as a revision to the State Implementation Plan and must address the technical and economic feasibility of:

   1. (i) utilizing compliant coating(s) and/or inks;
   2. (ii) utilizing demonstrated and proven emission control technologies which would achieve the required overall removal efficiency determined pursuant to subdivision (c) of this section;
   3. (iii) utilizing demonstrated and proven emission control technologies which would achieve a level of overall removal efficiency less than the required level determined pursuant to subdivision (c) of this section; and
   4. (iv) utilizing demonstrated and proven production modification methods which would result in real, documented, and enforceable reductions in the VOC emissions from the process.
7. (2) Facilities with surface coating processes subject to this Part with an annual potential to emit of less than five tons of VOCs will only be required to comply with subparagraphs (1)(i) and (iv) of this subdivision in order to demonstrate that a lesser degree of control is RACT for these processes.