Coating VOC Emissions Calculator

Table of contents

• How to use
• Common mistakes
• Definitions
• Methodology
• Limitations & assumptions
• Sources

VOC: Volatile organic compounds, which are carbon-containing chemicals that can evaporate into air from coatings and solvents.

As-applied VOC content: VOC mass per gallon after the coating, catalyst, and thinner or reducer are mixed in the entered recipe.

Mix parts: Relative amounts in a recipe, usually parts by volume. A 4:1:1 recipe has 6 total parts.

Cleanup or purge solvent: Solvent used to clean equipment or clear lines, counted separately from mixed coating material.

Reclaimed solvent: Cleanup or purge solvent recorded as recovered. The calculator subtracts reclaimed gallons from used gallons before estimating cleanup-solvent VOC.

Short ton: A US short ton equals 2,000 pounds.

Mistake: Entering a regulatory less-water or less-exempt-compounds value in Coating VOC content.
Fix: Use the product's as-supplied lb VOC/gal value for Coating VOC content, Catalyst VOC content, and Thinner or reducer VOC content.

Mistake: Treating Mixed material used in one year as gallons of coating alone.
Fix: Enter total gallons of the fully mixed material. The calculator splits that amount using Coating mix parts, Catalyst mix parts, and Thinner or reducer mix parts.

Mistake: Leaving Catalyst VOC content blank while Catalyst mix parts is greater than 0.
Fix: Enter the catalyst's VOC content or change Catalyst mix parts to 0 if no catalyst is used.

Mistake: Entering Cleanup or purge solvent used for selected period without Cleanup or purge solvent VOC content.
Fix: Check Estimate period and then recalculate. Enter both values for a cleanup record, or clear both fields if cleanup solvent is not included.

Mistake: Entering more Cleanup or purge solvent reclaimed for selected period than Cleanup or purge solvent used for selected period.
Fix: Check Estimate period and then recalculate. Check that both entries cover the same selected period and that reclaimed gallons do not exceed used gallons.

Mistake: Using Estimated VOC emitted for selected period as a compliance decision.
Fix: Compare As-applied VOC content only with the applicable coating-category limit on the same VOC basis, and verify permit requirements separately.

• This is a mass-balance estimate. It assumes VOC included in the entered mixed coating and net cleanup solvent is emitted during the selected period.
• Use as-supplied VOC values that match the product documents. Regulatory VOC values may use a different basis, such as less water or less exempt compounds.
• The result does not determine compliance, permit applicability, reporting requirements, fees, coating-category limits, or control-device performance.
• Transfer efficiency, capture efficiency, destruction efficiency, overspray, water, exempt compounds, and hazardous air pollutants are not calculated.
• Cleanup solvent is included only when both its VOC content and gallons used are entered. Reclaimed gallons reduce the cleanup estimate only as recorded.
• Each selected period is calculated from its own material-use entry. The calculator does not convert jobs or hours into annual use.

Recipe calculation

The calculator adds the three recipe-part entries, then uses each product's share of those parts to find the VOC content of one gallon of mixed coating.

total_mix_parts = coating_parts + catalyst_parts + thinner_parts

as_applied_voc_lb_per_gal = (coating_voc_lb_per_gal * coating_parts + catalyst_voc_lb_per_gal * catalyst_parts + thinner_voc_lb_per_gal * thinner_parts) / total_mix_parts

A component with 0 mix parts contributes no VOC and does not need a VOC value. Total mix parts must be greater than 0.

Emissions calculation

The selected mixed-material use is multiplied by the as-applied VOC content. This gives VOC from the mixed coating recipe for the selected period.

recipe_voc_lb = selected_material_use_gal * as_applied_voc_lb_per_gal

If a complete cleanup or purge-solvent record is entered, the calculator subtracts reclaimed gallons before adding the solvent's VOC contribution.

cleanup_solvent_voc_lb = (cleanup_solvent_used_gal - cleanup_solvent_reclaimed_gal) * cleanup_solvent_voc_lb_per_gal

estimated_voc_emitted_lb = recipe_voc_lb + cleanup_solvent_voc_lb

For One year, the calculator also divides annual pounds by 2,000 to show US short tons.

annual_voc_tons = estimated_voc_emitted_lb / 2000

Worked example

For a 4:1:

1 recipe with coating at 3.0 lb VOC/gal, catalyst at 1.0 lb VOC/gal, and thinner at 6.0 lb VOC/gal, the mixed VOC content is (3.0 x 4 + 1.0 x 1 + 6.0 x 1) / 6 = 3.1667 lb VOC/gal. If 100 gallons are used in one year, recipe VOC is 316.67 lb. Adding 10 gallons of cleanup solvent at 5.0 lb VOC/gal with 2 gallons reclaimed adds 40 lb, for 356.67 lb total, or about 0.1783 short tons.