Calculating VOC Content of a Material

There is sometimes confusion over the terms VOC of coating/colorant/adhesive and VOC of material. The VOC of coating/colorant/adhesive is the same as the term “regulatory VOC,” which is equivalent to the term "VOC, less water and exempts." The VOC of material is the same as the term "actual VOC," which is equivalent to the term "VOC, including water and exempts."

The regulatory VOC calculates the VOC less exempts and water, which is a more complicated calculation than the actual VOC, in that it subtracts the volume of water and the volume of exempt compounds from the volume of material, in the denominator. The calculation was derived to express the VOC emitted per volume of coating solids to eliminate the effect of dilution. Dilution with water or exempt solvents would reduce the VOC-to-paint-volume ratio while maintaining a constant VOC-to-paint/adhesive-solids ratio. This is important because those materials are applied at a certain film thickness so dilution would result in a larger volume of the material being applied to achieve the same film thickness. For conventional solvent based products with no exempt compounds, the two values are always the same.

For waterborne coatings and coatings containing exempt compounds, the VOC of coating is always the higher of the two values. The VOC limits listed in the Table of Standards (PDF, 35kb) refer to the VOC of coating. The only exception is for low solids coatings where the purpose of the coating is not to build film thickness. Low solids coatings, which are defined as coatings containing less than one pound of solids per gallon of coating, are regulated by the VOC of material. VOC emissions, including the emissions fee in Rule 314, are also calculated based on the VOC of material.

The VOC Calculator (XLS, 90kb) is a spreadsheet that will calculate both VOC values based on the solids, water content and density of the material. 

Sample Coating Calculation:

Density= 0.99 g/mL
Water= 50% by weight
Density of water= 0.997 g/mL
Solids= 48% by weight

VOC of Coating Calculation
(Regulatory VOC, less water and exempt compounds):
 
Remove the volume solid from denominator
 Volume Solids= [Weight Solids]/[Density]

VOC of Material Calculation (Actual VOC):

Guidance on VOC Labeling and Test Methods for Coatings

Coatings products sold or used within South Coast AQMD's jurisdiction may be required to include VOC content on product labels pursuant to Rule 443.1 ─ Labeling of Materials Containing Organic Solvents. VOC content for labeling purposes may be determined by calculation from formulation data and/or by test results. The approved VOC test methods appropriate for determining product VOC content, whether for labeling or compliance purposes, vary by coating application. Please refer to the specific VOC rule applicable to the coating product to identify the required test methods and VOC calculation procedures. Further information on VOC test methods is available at: https://www.aqmd.gov/home/rules-compliance/compliance/vocs/architectural-coatings/current-and-past-activities/working-group.

For energy-curable coatings, VOC content may be determined using ASTM D5403 ─ Standard Test Methods for Volatile Content of Radiation Curable Materials, which is an approved method for establishing VOC content for both labeling and compliance purposes. However, thin-film energy-curable coatings (including UV/EB/LED-cured materials applied with very low film thickness) currently do not have an approved compliance test method for determining VOC content under South Coast AQMD rules. When VOC content must be included on product labels pursuant to Rule 443.1, manufacturers may use formulation data or estimate the VOC emissions of the reactive components of the thin film energy curable coatings using ASTM D7767 ─ Standard Test Method to Measure Volatiles from Radiation Curable Acrylate Monomers, Oligomers, and Blends and Thin Coatings Made from Them. ASTM D7767 is not a U.S. EPA approved test method and as such is not an appropriate compliance test method that a third-party laboratory, or the South Coast AQMD Laboratory, could rely on to verify the VOC content of a thin-film energy curable coating. For determining compliance with VOC limits for thin-film energy-curable coatings, manufacturers may rely on formulation data and ASTM D7767 to determine product VOC content for labeling purposes.