(1) Measure Finish as Applied. Use a finish inventory log to record the pounds of each type of finish applied for each leather product process operation and the mass fraction of HAP in each applied finish. Figure 1 of this subpart shows an example log for recording the minimum information necessary to determine your finish usage and HAP loss. The finish inventory log must contain, at a minimum, the information for each type of finish applied listed in paragraphs (b)(1)(i) through (vii) of this section:

(2) Chemical Inventory Mass Balance. Determine the actual monthly HAP loss from your affected source through mass balance calculations. You must follow your detailed mass balance procedures and calculations in your plan for demonstrating compliance in accordance with § 63.5325. The HAP mass balance must be based on a detailed inventory of stored chemicals at the beginning and end of each month, and business purchasing records to indicate additions to the inventory of chemical supplies. The net loss of chemicals used for finish applications is determined by subtracting the end of the month chemical inventory from the beginning of the month chemical inventory and adding the quantities of all chemicals purchased during the same 1-month period. In situations when an excess amount of finish is formulated, you must have documented procedures on how the excess amount is accounted for in the mass balance.

(1) For facilities not using add-on emission control devices, the entire HAP content of the finishes are assumed to be released to the environment. Using the finish inventory log, multiply the pounds of each recorded finish usage by the corresponding mass fraction of HAP in the finish. The result is the HAP loss in pounds from each finish application. Sum the pounds of HAP loss from all finish applications recorded during the previous month to determine the total monthly HAP loss in pounds from your finishing operation.

(2) For facilities using add-on emission control devices, the finish inventory log and the emission reduction efficiency of the add-on capture and control devices can be used to determine the net HAP loss in pounds. The emission reduction efficiency for a control device must be determined from a performance test conducted in accordance with §§ 63.5375 and 63.5380. Using the finish inventory log, multiply the pounds of each recorded finish usage by the corresponding mass fraction of HAP in the finish. The result is the gross HAP loss in pounds from each finish application prior to the add-on control device. Multiply the gross HAP loss by the percent emission reduction achieved by the add-on control device and then subtract this amount from the gross HAP loss. The result is the net HAP loss in pounds from each finish application. Sum the pounds of net HAP loss from all finish applications recorded during the previous month to determine the total monthly net HAP loss in pounds from your finishing operation.