1. Evaluation of VOC Definition Based on Vapor Pressure
Nicolas Peterson
EMAssist, Inc
Joint Services Environmental Management Conference & Exposition 2005

2. When is an organic compound no longer volatile?
Introduction
Volatile Organic Compounds (VOC) are extensively regulated.
Generally, VOC are either exempt or not exempt.
Not all VOC are created equal, but they are typically regulated as such.
Some are less volatile.
Some are less reactive.
The EPA is currently re-examining how VOC are regulated.
When is an organic compound no longer volatile?

3. Overview Benefits of updating VOC definition and/or regulation
VOC definitions and regulations
Suggested approach
Recent EPA actions
Conclusions

4. Benefits of Modifying Approach to VOC
Less burdensome regulations for “VOC” that are minimally volatile and/or reactive (i.e. have minimal ability to produce smog):
Focuses resources where they have more impact.
Reduces risk of non-compliance without impacting the environment.
Encourages the use of “greener” materials.

5. Scientific Definition of Vapor Pressure
Surrounding Hg (1 atm)
Vapor Pressure (Pvap)
High energy molecules escaping to the surrounding atmosphere
Liquid at temperature (T)

6. Vapor Pressure and Temperature

7. Regulatory Definition of VOC
The EPA has defined a Volatile Organic Compound (VOC) as any compound of Carbon that participates in atmospheric photochemical reactions excluding the few listed as “Exempt VOC” by this section. [40 CFR (s)(1)].
No quantitative definition or lower-limit for “volatile” is provided; however,
Disjointed approaches exist regarding this.
Sampling and test methods do have limitations.
Industry standards are typically used in the absence of regulatory specifics.

8. Regulatory Definition of Semi-VOC
Semi-Volatile Organic Compounds (semi-VOC) have been quantitatively defined as a subset of the aforementioned VOC compounds whose atmospheric boiling point is >100oC.
This definition has not been incorporated into the regulations governing VOC.

9. LVP-VOC are exempt from the VOC Content Limits for consumer products.
California Air Resources Board (CARB) Definition of Low Vapor Pressure VOC
The California Code of Regulations contains the definition of Low Vapor Pressure VOC “LVP-VOC”:
A chemical “compound” or “mixture” containing at least one Carbon atom and one of the following:
Vapor pressure <0.1 mm 20oC, or,
Composed of chemical compounds with more than 12 Carbon atoms, or
A boiling point >216oC.
LVP-VOC are exempt from the VOC Content Limits for consumer products.

10. National VOC Emission Standards for Consumer Products
Criteria for VOC Exemption:
Vapor pressure <0.1 mm 20oC; or,
Consists of more than 12 Carbon atoms; or
A melting point higher than 20oC (and does not sublimate).

11. Solvents exempt from VOC Housekeeping requirements:
Aerospace National Emissions Standards for Hazardous Air Pollutants (NESHAP)
Solvents exempt from VOC Housekeeping requirements:
Vapor Pressure <7 mm 20oC; and,
Must not contain HAP.
This was set to encourage sources to use less volatile solvents.

12. De Nevers’ VOC Definition
According to Dr. Noel De Nevers’, “Air Pollution Control Engineering” VOC are those organic liquids or solids whose room temperature (20oC) vapor pressures are greater than about 0.52 mm Hg, and;
Whose atmospheric boiling points are up to about 260oC, or,
Most compounds with less than about 12 Carbon atoms.

13. EPA Test Methods
EPA test methods in 40 CFR 60, Appendix A are used for measuring VOC when determining compliance with emission limits.
Test methods for VOC sampling and analysis have inherent limits in what compounds they can capture and detect.

14. EPA Test Methods
EPA Methods 8260 and 8270 use either a Volatile Organic Sampling Train (VOST) or Tedlar Bags to collect the sample for analysis.
The Semi-VOST will not capture compounds with a boiling point >200oC. (for Semi-VOC).
The Tedlar Bags and VOST will not capture compounds with a boiling point >121oC.
Semi-VOST – Sampling Method 0010.
VOST – Sampling Methods 0030 and 0031.
Tedlar Bags – Sampling Method 0040.

15. EPA VOC Emissions Report to Congress
EPA VOC Emissions Report to Congress (March 1995) categorized certain VOC as “not reportable” where the VOC:
Were solids,
Had a vapor pressure <0.1 mm 20oC, or
Had > 12 carbon atoms.

16. Compilation of Reference Material
Considering regulatory definitions, requirements, EPA Methods, etc., regarding Low Volatility VOC (LV-VOC) together suggests:
A commonality among physical parameters.
Further definition and integration within rules would be useful and appropriate.
Regulations should take into account “how” the LV-VOC are used (e.g. heated).
Boiling Point
Vapor Pressure
# Carbon Atoms

17. Low Volatility VOC
Suggest LV-VOC be defined as those organic compounds that meet any one of the following:
Vapor pressure <0.1 mm 20oC,
Boiling point >216oC (at 1 atm), or
Contain more than 12 Carbon atoms.
Suggested LV-VOC parameters are beyond noted method detection limits (boiling point >216oC vs 121oC or 200oC).
Examples: Breakthrough, PD680 Type III, etc.

18. Low Volatility VOC LV-VOC criteria were suggested based on:
EPA test methods
Academic reference
CARB definition of LVP-VOC
Consumer Products VOC Emission Standards
EPA’s 1995 VOC Emissions Report to Congress
Aerospace NESHAP treatment of solvents

19. Comparison of Parameters and Definitions
LOW - VOLATILITY VOC DEFINITION
Citation, Authority or Rule
Vapor Pressure
mm 20C
Boiling Point (C)
# Carbon Atoms
Other
Context/Technology
40 CFR Aerospace NESHAP
<7
Must not contain HAP
Exempt from Housekeeping req’ts
"Air Pollution Control Engineering", De Nevers
<0.52
>260
>12
Heuristic
CA Code of Regulations Section 94510(d) - CARB Consumer Products
<0.1
>216
Exempt from VOC content limits.
40 CFR (f) - Consumer Products
melting pt >20C
EPA’s VOC Emissions Report to Congress (March 1995)
For solids, N/A
Emission Inventory Reporting.
EPA Test Method 0040 (for 8260b &/or 8270c) - Tedlar Bag
>121
Sampling limit
EPA Test Method 0030 & 0031 (for 8260b &/or 8270c) – VOST
EPA Test Method 0010 (for 8260b &/or 8270c) – Semi-VOST
>200
LV-VOC
>216 
 >12
Suggested criteria

20. Recent EPA Action
The EPA is currently exploring alternative definitions/classifications to their VOC definition.
The EPA noted plans to publish a notice inviting public comment on the VOC exemption policy. [Federal Register: Sep 3, 2003]
The EPA proposed updating the VOC definition for Aerosol Coatings to include California’s new, reactivity-based VOC definition. [Federal Register: Jan 7, 2005]

21. Reactivity-Based Definition of VOC
Specific VOC are given a numerical reactivity value.
Values are relative and based on laboratory testing that determines grams of ozone formed per gram of organic compound reacted.
These relative reactivities are determined for a number of specific compounds to make up the Maximum Incremental Reactivity (MIR) Scale.

22. Reactivity-Based Definition of VOC
The new definition targets VOC on a reactivity basis instead of the original “Exempt or Not” approach.
Applies to Aerosol Coating products in California.
Intended to encourage Manufacturers to reformulate their Aerosol Coatings to use “greener” or less reactive VOC.
Shows EPA’s willingness to consider new approaches to classifying VOC based on their propensity to form ozone.

23. Conclusions Benefits of classifying certain VOC as LV-VOC
Allows for resources to be focused on more important contributors to photochemical smog (i.e. VOC that actually get into the air and react).
Allows for a reduction in the compliance burden for air sources that really aren’t contributing to smog formation.
Provides incentive to use “greener” (less reactive, less volatile) VOC.

24. Conclusions What we hope to accomplish with this presentation:
Broaden awareness, and
Stimulate discussion among and between the regulated and regulatory communities pertaining to:
Management practices
Rule development
Permit negotiations

25. Questions?