Bay Area Air Quality Management District January 21, 2004 

 8-10-1 

REGULATION 8 

ORGANIC COMPOUNDS 

RULE 10 

PROCESS VESSEL DEPRESSURIZATION 

INDEX 

8-10-100 GENERAL 

8-10-101 Description 

8-10-110 Exemption, Equipment Subject to Other Rules 

8-10-111 Deleted, January 21, 2004 

8-10-112 Limited Exemption, Measurement Periods 

8-10-113 Exemption, Small Vessels 

8-10-114 Exemption, Batch Processes 

8-10-200 DEFINITIONS 

8-10-201 Chemical Plant 

8-10-202 Petroleum Refinery 

8-10-203 Process Unit 

8-10-204 Process Vessel 

8-10-205 Organic Compound 

8-10-206 Total Organic Compound 

8-10-300 STANDARDS 

8-10-301 Process Vessel Depressurizing 

8-10-302 Opening of Process Vessels 

8-10-400 ADMINISTRATIVE REQUIREMENTS 

8-10-401 Reporting 

8-10-402 Deleted January 21, 2004 

8-10-500 MONITORING AND RECORDS 

8-10-501 Monitoring 

8-10-502 Concentration Measurement 

8-10-503 Records

8-10-600 MANUAL OF PROCEDURES 

8-10-601 Monitoring Procedures 
Bay Area Air Quality Management District January 21, 2004 

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REGULATION 8 

ORGANIC COMPOUND 

RULE 10 

PROCESS VESSEL DEPRESSURIZATION 

8-10-100 GENERAL 

8-10-101 Description: The purpose of this Rule is to limit emissions of organic compounds 

from depressurizing and opening of process vessels at petroleum refineries and 

chemical plants. 

(Amended 3/17/82; 7/20/83; 1/21/04) 

8-10-110 Exemption, Equipment Subject to Other Rules: The provisions of this rule shall 

not apply to vessels that are subject to the following Regulation 8 rules: 

110.1 Regulation 8, Rule 5: Storage of Organic Liquids 

110.2 Regulation 8, Rule 24: Pharmaceutical and Cosmetic Manufacturing 

Operations 

110.3 Regulation 8, Rule 35: Coating, Ink and Adhesive Manufacturing 

110.4 Regulation 8, Rule 36: Resin Manufacturing 

110.5 Regulation 8, Rule 41: Vegetable Oil Manufacturing Operations 

110.6 Regulation 8, Rule 50: Polyester Resin Operations 

110.7 Regulation 8, Rule 52: Polystyrene, Polypropylene, and Polyethylene Foam 

Product Manufacturing Operations 

(Amended January 21, 2004) 

8-10-111 Deleted January 21, 2004

8-10-112 Limited Exemption, Measurement Periods: The provisions of Section 8-10-301 

shall not apply while a process vessel is opened for a period of time reasonably 

necessary for measurements to determine compliance with the concentration and 

mass emission limits of this rule. 

(Adopted January 21, 2004) 

8-10-113 Exemption, Small Vessels: The provisions of this Rule shall not apply to any 

process vessel with a volume of less than 100 cubic feet (ft3

). 

(Adopted January 21, 2004) 

8-10-114 Exemption, Batch Processes: The provisions of this rule shall not apply to any 

process vessel used in a batch process operation that requires periodic vessel 

opening as part of the routine operation of the vessel, including but not limited to 

delayed coking vessels. 

(Adopted January 21, 2004) 

8-10-200 DEFINITIONS 

8-10-201 Chemical Plant: Any facility engaged in producing organic or inorganic chemicals 

and/or manufacturing products by chemical processes. Any facility or operation that 

has 325 as the first three digits in the North American Industrial Classification 

Standard (NAICS) code. Chemical plants may include, but are not limited to the 

manufacture of: industrial inorganic and organic chemicals; plastic and synthetic 

resins, synthetic rubber, synthetic and other man made fibers; drugs; soap, 

detergents and cleaning preparations, perfumes, cosmetics and other toilet 

preparations; paints, varnishes, lacquers, enamels and allied products; agricultural 

chemicals; safflower and sunflower oil extracts; re-refining. 

(Adopted 7/20/83; Amended 1/21/04) 

8-10-202 Petroleum Refinery: Any facility that processes petroleum, as defined in the North 

American Industrial Classification Standard No. 32411 (1997). 

(Adopted 7/20/83; Amended 1/21/04) 

8-10-203 Process Unit: A manufacturing process which is independent of other processes 

and is continuous when supplied with a constant feed of raw materials and sufficient 

storage facilities for the final product. 

(Adopted 7/20/83) 

8-10-204 Process Vessel: Any vessel in which organic compounds are fractionated, 

chemically reacted, washed or purified. These vessels shall include but are not 
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limited to reactors, columns, accumulator vessels, knockout pots, surge/settling 

drums and other similar devices. 

(Renumbered 7/20/83; Amended 1/21/04) 

8-10-205 Organic Compound: Any compound of carbon, excluding methane, carbon 

monoxide, carbon dioxide, carbonic acid, metallic carbides or carbonates and 

ammonium carbonate.

(Adopted January 21, 2004) 

8-10-206 Total Organic Compound: All organic compounds of carbon including methane, 

excluding carbon monoxide, carbon dioxide, carbonic acid, metallic carbides or 

carbonates and ammonium carbonate. 

(Adopted January 21, 2004) 

8-10-300 STANDARDS 

8-10-301 Process Vessel Depressurizing: Emissions of organic compounds from 

depressurizing any process vessel at a petroleum refinery or a chemical plant shall 

be controlled by venting them to a fuel gas system, firebox, incinerator, thermal 

oxidizer, flare, or otherwise containing and treating them so as to prevent their 

emissions to the atmosphere. Such procedures shall continue until the pressure 

within the process vessel is as close to atmospheric pressure as practicably possible, 

in no case shall a process vessel be vented to the atmosphere until the partial 

pressure of organic compounds in that vessel is less than 1000 mm Hg (4.6 psig). 

(Amended 3/17/83; 3/20/83; 1/21/04) 

8-10-302 Opening of Process Vessels: Effective July 1, 2004, no process vessel may be 

opened to the atmosphere except as provided below: 

302.1 No process vessel may be opened to the atmosphere unless the internal 

concentration of total organic compounds has been reduced prior to release 

to atmosphere to less than 10,000 parts per million (ppm), expressed as 

methane (C1) except as provided in Section 8-10-302.2. 

302.2 A process vessel at a refinery or chemical plant may be opened when the 

internal concentration of total organic compounds is 10,000 ppm or greater 

provided that the total number of such vessels opened with such 

concentration during any consecutive five year period does not exceed 10% 

of the total process vessel population as documented pursuant to section 8-

10-401, and the organic compound emissions from the opening of these 

vessels shall not exceed 15 pounds per day. Vessels with an internal 

concentration of total organic compounds of 10,000 ppm or greater shall not 

be opened on any day on which the APCO predicts an exceedance of a 

National Ambient Air Quality Standard for ozone or declares a Spare the Air 

Day. 

(Adopted January 21, 2004) 

8-10-400 ADMINISTRATIVE REQUIREMENTS 

8-10-401 Reporting: Any facility subject to the provisions of this rule shall submit an annual 

report to the Air Pollution Control Officer (APCO) containing the elements of Section 

8-10-503. The annual report shall be submitted by February 1 of each year. By April 

1, 2004, any facility subject to the provisions of this rule shall submit an initial report 

that lists all process vessels, it’s volume in cubic feet, and it’s service type. The list 

shall be updated yearly, as necessary, and submitted with the annual report. 

(Amended 3/17/82, 7/10/83; 1/21/04) 

8-10-402 Deleted January 21, 2004 

8-10-500 MONITORING AND RECORDS 

8-10-501 Monitoring: Any vessel subject to this rule shall be monitored for the concentration 

of total organic compounds prior to opening and once per day during the time the 

vessel is open to the atmosphere. The sample shall be a representative sample of 

the internal atmosphere of the vessel. This section shall not apply if it can be 
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demonstrated that the concentration of total organic compounds has been reduced to 

a concentration equal to or less than 100 ppm for three consecutive days. 

(Adopted January 21, 2004) 

8-10-502 Concentration Measurement: The meter used to measure the concentration of total 

organic compound emissions shall meet the accuracy requirements specified in EPA 

Method 21. 

(Adopted January 21, 2004) 

8-10-503 Records: Any facility subject to the provisions of this rule shall keep records of each 

vessel depressurization. The records shall include the following information: 

503.1 The date, time, type of activity, and duration of depressurization and vessel 

opening, 

503.2 The type of service, size and name or vessel identification number, 

503.3 The measured total organic compound concentration and calculated mass 

emissions from each depressurized vessel, including the sample location 

and any assumptions made in calculating the mass emissions, and 

503.4 The number and size of any air movers used to assure compliance with 

confined space entry requirements. 

503.5 Records shall be maintained for at least 5 years and shall be made available 

to the APCO for inspection at any time. 

(Adopted January 21, 2004) 

8-10-600 MANUAL OF PROCEDURES 

8-10-601 Monitoring Procedures: The procedures used to monitor emissions are set forth in 

EPA Method 21 (40 CFR Part 60, Appendix A). 

(Adopted January 21, 2004)