Frequently Asked Questions
Definition of Reactive Organic Compounds (ROC)

Introduction

This page contains questions and answers regarding the recently revised definition of reactive organic compounds (ROC). The definition of ROC was revised by the APCD Board on July 18,1996, resulting in the exclusion of compounds that were previously considered ROCs. Of particular note, acetone and ethane are no longer ROC compounds. Since this change affects many businesses, this FAQ provides guidance on how the new definition will be implemented.

If you have additional questions you would like to see posted here, please e-mail us at engr@sbcapcd.org

Implementation Questions for the New ROC Definition

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1. The ROC emission limit in my existing permit is based on one of the newly exempted compounds (for example, ethane, acetone). What happens to my permit?

   For any existing permit where the ROC emission limit includes one of the exempted compounds, the ROC limit will be updated at the next permit reevaluation. You do not need to do anything until then.

    

2. What if I wish to have my permitted emissions changed now rather than wait until the permit reevaluation?

   You may submit a permit application at any time after the revised definition is adopted to have your permit revised to reflect the new ROC definition. Permit application fees may be assessed on a cost reimbursement basis depending on the complexity of the application.

   
   
3. How will the permitted emissions be updated to reflect the newly exempt compounds?

   The following process will be used:

   For existing permits that contain compound specific usage limits, the limits for newly exempt compounds will be deleted, and all limits for non-exempt pollutants will remain intact.

   For existing permits that contain a facility-wide ROC limit, the limit will remain unchanged. The source can emit emissions of any combination of ROCs up to the permitted limit.

   Emission limits for new and modified sources will be based on the new definition of ROC.

   
   
   

4. How will emission factors be adjusted to account for the newly exempt compounds?

   Of the compounds proposed for exemption, there are only two that will have any material effect on ROC emission limits: acetone and ethane. The calculation for acetone will be fairly straightforward because there is ample data on the amount of acetone in the various products that contain acetone. In essence, acetone will simply be deducted from the ROC emission estimates.

   For ethane, APCD staff will adjust the ROC emission limits by backing out the ethane fraction from the emission factor used to establish the original permitted ROC limit. These data are typically provided in the background documentation for the permit.

   
   
5. It previously exceeded the BACT threshold and installed BACT. Subtracting out the newly-exempted compounds would put me below the BACT threshold. Must I still operate the control equipment and comply with BACT requirements?

   Yes. BACT will be enforced as specified in your permit, and will not change as a consequence of the new ROC definition.

   
   
6. It previously exceeded the offset threshold and was required to secure emission reduction credits (ERCs) for my facility. The new exemptions will reduce my ROC liability. May I release ERCs I no longer need to meet my new liability?

   No. Your permit was issued based on the rules in effect at the time your application was deemed complete. You must comply with the offset requirements specified in your permit.

   While the APCD will not retroactively reassess BACT and offset requirements, your net emission increase may be decreased based on the new ROC definition. Your new NEI will be used in reviewing subsequent modifications to determine if new source review requirements will apply. Your NEI will be updated during your permit reevaluation or if you receive a new permit (see questions Q-1 and Q-2).

   
   
7. As a follow-up to the above question, may I keep any excess emission reduction credits (ERCs) for future use? What if I am in source compliance demonstration (SCDP)?

   As indicated by the answer to question Q-6, existing offsets are unaffected by the new ROC definition. If the ERCs are requalified using the rules in effect at the time of requalification, then they may be subject to reuse for future projects.

   
   
8. If my permit is not reevaluated for a few years, how will compliance with my ROC emission limits be assessed? My current ROC limit is based in part on emissions from compounds that are now exempt. Does the new definition therefore give me more room under my ROC limit and allow me to increase my emissions of other ROCs?

   If your permitted emission limit contains limits on the use of specific exempt compounds (for example, acetone) you must comply with these limits until they are changed during your permit reevaluation or if you receive a new permit (see questions Q-1 and Q-2). If your permit does not contain compound-specific limits, you can emit up to your ROC limit using the new definition of ROC compounds.

   
   
9. My permit will not reevaluated for a few years. Am I allowed to start using exempt compounds such as acetone now?

   If your permit does not include specific limits for the exempt compounds, you may use them and they will not count towards your permitted ROC limit.

   
   
10. How will my Annual Emission Fees be affected?

    Annual Emission Fees are based on actual emissions and will be calculated using the ROC definition in place at the time the emission based fee invoices are prepared.

    Thus, any new fees assessed will reflect the new definition.
    
     
    
11. How will my AQAP Emission Fees be affected?

    AQAP Emission Fees are based on actual emissions (if permitted before 1988), or permitted emissions (if permitted in 1988 or later)(see Rule 210 for details). Fees based on actual emissions will be calculated using the ROC definition in place at the time the invoices are prepared. Fees based on permitted emissions will not change until your permit is reevaluated or you receive a new permit (see questions Q-1 and Q-2).

    
    
12. Can existing data be used to determine the applicability of Rule 331?

    Previously exempt streams or components would almost certainly remain exempt. For purposes of documenting any new exemptions, existing data can be used provided the data collection methods comply with the testing requirements of Rule 331.

    
    
13. Would we redefine "leak" in Rule 331 from ">10,000 ppm as methane" to ">10,000 ppm as ethane"? Would we calibrate OVAs for all Rule 331 inspections using ethane? How does this tie into EPA's directions for calibration in Method 21?

    The definition of "leak" would not change nor would we need to change the OVA leak detection basis to a ethane based standard. EPA Method 21 was based on a methane basis and this was while their VOC definition excluded ethane. As such, no change is warranted.

    
    
14. How does the proposed ROC definition compare to EPA's definitions? Will there be any conflicts with regulations such as NSPS subpart KKK?

    The APCD's proposed definition is identical with the current EPA definition except for perchloroethylene. EPA excludes perchloroethylene, while the APCD (and our neighboring air districts) have decided to defer an exemption for perchloroethylene pending further analysis.

    
    
15. How will the change in ROC definition affect the APCD's surface coating rules (e.g., Rules 323, 337, 339)? How does this affect the "g/l" standards? Won't this cause great confusion with compliance because the coating containers specify a VOC limit, but do not list specific VOC compounds.

    The change in ROC definition will not affect the ROC coating limits specified in the APCD's coatings rules: the limits will remain unchanged. The only potential problem with the new definition would occur if a business elects to use a non-compliant coating that exceeds one of the APCD's coating limits. The coating could contain acetone, and by deducting acetone the coating could in fact be a compliant coating. In this situation, unless the user has proof that the coating less acetone meets the coating limit, the user would be cited for a rule violation. Staff expect few if any compliance problems of this sort because a business must purchase a non-compliant coating to start the chain of events.

    
    
16. How are existing ERC banks affected?

    The only existing bank with valid credits is the Vandenberg Air Force Base Memorandum of Understanding. Use of any credit from this bank will be reassessed on a non-ethane basis. The change will be minimal since the amount of ethane is very small.

    
    
17. What happens if part of my facility drops out of Rule 331 fugitive inspection and maintenance (I&M) requirements as a consequence of the change in ROC definition? Would I need to file an authority to construct permit application? What would happen to my net emission increase (NEI)? Would I be subject to new source review?

    While it is possible that components or processes within a facility may become exempt from I&M requirements, examination of 50 chemical analyses from 24 facilities suggests that no exemptions for entire facilities that currently require I&M will be created by the proposed changed to the ROC definition. Eliminating I&M programs for an entire facility, or for part of a facility previously subject to I&M constitutes a change in the method of operation and would:

    Require an authority to construct permit application;
    Result in an increase in the source's NEI; and
    Be subject to new source review.

    A sample calculation showing the potential implications of the rule change to an oil and gas production or processing facility is provided below. In this example, the facility drops out of I&M due to the proposed change in the definition of ROC.

    Assumed HC weight fractions: methane: 84%, ethane: 7%, C3+ 9%;
    ROC emissions before the rule change: 4.9 tons per year (ROC emissions with ethane and an 80% reduction due to I&M);
    ROC emissions after the rule change: 13.8 tons per year (ROC emissions without ethane and I&M);
    ROC NEI: 11.0 tons per year, or 2.51 pounds per hour.

    NEI in tons per year is calculated by:

    NEI = ROC after - ROC before;
    ROC after = 13.8 tons/yr = ROC before / 0.2;
    ROC before = 2.8 tons/yr = (4.9 tons/yr) x [0.09/(0.07+0.09)].

    NEI in pounds per day is calculated by:

    NEI = 2000 lbs/ton x (13.8 tons/yr - 2.8 tons/yr) / (365 days/yr x 24 hrs/day).

    New Source Review Implications: Modification (dropping out of I&M) would be subject to BACT (NEI change is greater than 2.5 pounds per hour)

    
    

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For more information or assistance, call the Engineering Division (805) 961-8800, or e-mail engr@sbcapcd.org.

A sample calculation showing the potential implications of the rule change to an oil and gas production or processing facility is provided below. In this example, the facility drops out of I&M due to the proposed change in the definition of ROC.

NEI in tons per year is calculated by:

NEI in pounds per day is calculated by:

New Source Review Implications: Modification (dropping out of I&M) would be subject to BACT (NEI change is greater than 2.5 pounds per hour)

For more information or assistance, call the Engineering Division (805) 961-8800, or e-mail engr@sbcapcd.org.