Appendix B VOC/HAP Calculation

Air emissions that result from the evaporation of solvents such as those in paints can be calculated using a material balance approach. To calculate the pounds of HAPs or VOCs emitted, a firm needs to know:

• Quantity of product used annually
• Total density of the product
• Weight percent HAPs or VOCs

Calculating the Quantity of Product Used

The quantity of product used can be taken from purchasing records provided a company maintains an essentially constant inventory. If the firm is disposing of waste materials and has records to show the amount of HAPs or VOCs in the waste, that amount can be subtracted from the total used since it was not emitted into the air.

Calculating the Total Density

The total density of the product can be found on the Material Safety Data Sheet (MSDS). Sometimes it is listed as a specific gravity, calculated by using the ratio of product density/density of water. If specific gravity is given, multiply by 8.314 pounds per gallon (the density of water), to get the density of the product.

Calculating Weight Percent

The HAP content in the paint can be found on the MSDS. HAP content may be listed as a volume percent (vol %) or weight percent (wt %). VOC or solids content also may be listed. If the paint does not contain water or exempt VOCs, the VOC content can be calculated from the weight content using the following relationship:

wt % VOC = 100 - wt % solids

If the paint contains water or an exempt VOC, the amount of VOCs in the paint is calculated as follows:

wt % VOC = 100 - wt % solids - wt % water - wt % exempt VOC

Calculating HAPs and VOCs

Using the volume percent (vol %) of HAPs (or VOCs), the total weight of HAPs (or VOCs) can be determined using the following equation:

(HAP density) x (product vol.) X (vol % HAP/100)= HAP wt (KSBEAP, p. 41-42)