Bay Area Air Quality Management District July 25, 2007 

 9-8-1 

REGULATION 9 

INORGANIC GASEOUS POLLUTANTS 

RULE 8 

NITROGEN OXIDES AND CARBON MONOXIDE 

FROM STATIONARY INTERNAL COMBUSTION ENGINES 

INDEX 

9-8-100 GENERAL 

9-8-101 Description 

9-8-110 Exemptions 

9-8-111 Limited Exemption for Low Usage 

9-8-112 Registered Portable Equipment 

9-8-200 DEFINITIONS 

9-8-201 Gaseous Fuels 

9-8-202 Nitrogen Oxide Emissions 

9-8-203 Rated Brake Horsepower 

9-8-204 Stationary Internal Combustion Engine 

9-8-205 Rich-Burn Engine 

9-8-206 Lean-Burn Engine 

9-8-230 Emergency Standby Engine 

9-8-231 Emergency Use 

9-8-232 Reliability-related Activities 

9-8-233 Essential Public Service 

9-8-234 Best Available Control Technology (BACT) 

9-8-235 Dual-Fueled Pilot Compression-Ignited Engines 

9-8-236 Portable 

9-8-237 Unforeseeable 

9-8-300 STANDARDS 

9-8-301 Emission Limits – Spark-Ignited Engines Powered by Fossil Derived Fuels 

9-8-302 Emission Limits – Spark-Ignited Engines Powered by Waste Derived Fuels 

9-8-303 Emissions Limits – Delayed Compliance, Existing Spark-Ignited Engines, 51 to 250 

bhp or Model Year 1996 or Later 

9-8-304 Emission Limits – Compression-Ignited Engines 

9-8-305 Emission Limits – Delayed Compliance, Existing Compression-Ignited Engines, 

Model Year 1996 or Later 

9-8-306 Emission Limits for Dual-Fueled Compression-Ignited Engines 

9-8-330 Emergency Standby Engines, Hours of Operation 

9-8-331 Essential Public Service, Hours of Operation 

9-8-400 ADMINISTRATIVE REQUIREMENTS 

9-8-401 Compliance Schedule 

9-8-402 Reporting Requirements for Delayed Compliance 

9-8-500 MONITORING AND RECORDS 

9-8-501 Initial Demonstration of Compliance 

9-8-502 Recordkeeping 

9-8-503 Quarterly Demonstration of Compliance 
Bay Area Air Quality Management District July 25, 2007 

 9-8-2 

9-8-530 Emergency Standby and Low Usage Engines, Monitoring and Recordkeeping 

9-8-600 MANUAL OF PROCEDURES 

9-8-601 Determination of Nitrogen Oxides 

9-8-602 Determination of Carbon Monoxide and Stack Gas Oxygen 
Bay Area Air Quality Management District July 25, 2007 

 9-8-3 

REGULATION 9 

INORGANIC GASEOUS POLLUTANTS 

RULE 8 

NITROGEN OXIDES AND CARBON MONOXIDE 

FROM STATIONARY INTERNAL COMBUSTION ENGINES 

(Adopted January 20, 1993) 

9-8-100 GENERAL 

9-8-101 Description: This rule limits the emissions of nitrogen oxides and carbon monoxide 

from stationary internal combustion engines with an output rated by the manufacturer 

at more than 50 brake horsepower 

(Amended 8/1/01; 7/25/07) 

9-8-110 Exemptions: The requirements of Sections 9-8-301 through 305, 501 and 503 shall 

not apply to the following: 

110.1 Until January 1, 2012, engines rated by the manufacturer at less than 250 

brake horsepower output rating. 

110.2 Engines rated by the manufacturer at 50 brake horsepower output rating or 

less. Effective January 1, 2012. 

110.3 Until January 1, 2012, engines fired exclusively by liquid fuels including, but 

not limited to, diesel fuel, gasoline, and methanol. 

110.4 Engines used directly and exclusively for the growing of crops or the raising 

of animals. 

110.5 Emergency standby engines. 

(Amended 8/1/01; 7/25/07) 

9-8-111 Limited Exemption for Low Usage: The requirements of Sections 9-8-301, 302, 

303, 304, and 305 shall not apply to the following low use operations provided the 

requirements of Sections 9-8-502.1 and 9-8-530 are met: 

111.1 Until January 1, 2012, engines rated at, or below, 1000 brake horsepower 

that operate less than 200 hours, exclusive of any emergency use, in any 12-

consecutive-month period. 

111.2 Until January 1, 2012, engines rated above 1000 brake horsepower that 

operate less than 100 hours, exclusive of any emergency use, in any 12-

consecutive-month period. 

111.3 Effective January 1, 2012, engines that operate less than 100 hours, 

exclusive of any emergency use, in any 12-consecutive-month period 

(Amended July 25, 2007) 

9-8-112 Registered Portable Equipment: The requirements of this section shall not apply 

to an internal combustion engine registered as portable pursuant to the Statewide 

Portable Engine and Equipment Registration Program, Sections 2450-2465, Article 

5, Title 13, California Code of Regulations. 

(Adopted July 25, 2007) 

9-8-200 DEFINITIONS 

9-8-201 Gaseous Fuels: For the purposes of this rule, gaseous fuels include, but are not 

limited to: 

201.1 Fossil derived fuel gas such as natural gas, methane, ethane, propane, 

refinery fuel gas, and butane, including gases stored as liquids such as 

liquified petroleum gas (LPG). 

201.2 Waste derived fuel gas such as sewage sludge digester gas or landfill gas. 

9-8-202 Nitrogen Oxide (NOx) Emissions: The sum of nitric oxide (NO) and nitrogen dioxide 

(NO2) in the engine exhaust, collectively expressed as nitrogen dioxide. 

9-8-203 Rated Brake Horsepower: The maximum brake horsepower rating at maximum 

revolutions per minute (RPM) specified for the engine by the manufacturer or 

indicated on the engine nameplate. 
Bay Area Air Quality Management District July 25, 2007 

 9-8-4 

9-8-204 Stationary Internal Combustion Engine (Engine): Any spark or compression 

ignited internal combustion engine that is operated, or intended to be operated, at a 

specific site for more than one year or is attached to a foundation at that site. 

9-8-205 Rich-Burn Engine: Any spark or compression ignited internal combustion engine 

that is designed to be operated with an exhaust stream oxygen concentration of less 

than 4 percent, by volume. The exhaust gas oxygen content shall be determined 

from the uncontrolled exhaust stream. 

9-8-206 Lean-Burn Engine: Any spark or compression ignited internal combustion engine 

that is designed to be operated with an exhaust stream oxygen concentration of 4 

percent, by volume, or greater. The exhaust gas oxygen content shall be determined 

from the uncontrolled exhaust stream.

9-8-230 Emergency Standby Engine: Any engine that is exclusively operated: 

230.1 For emergency use; and 

230.2 For reliability-related activities. 

(Adopted August 1, 2001) 

9-8-231 Emergency Use: The use of an emergency standby or low usage engine during any 

of the following: 

231.1 In the event of unforeseeable loss of regular natural gas supply; 

231.2 In the event of unforeseeable failure of regular electric power supply; 

231.3 Mitigation or prevention of an imminent flood; 

231.4 Mitigation of or prevention of an imminent overflow of sewage or waste 

water; 

231.5 Fire or prevention of an imminent fire; 

231.6 Failure or imminent failure of a primary motor or source of power, but only for 

such time as needed to repair or replace the primary motor or source of 

power; or 

231.7 Prevention of the imminent release of hazardous material. 

(Adopted 8/1/01; Amended 7/25/07) 

9-8-232 Reliability-related Activities: Either:

232.1 Operation of an emergency standby engine to test its ability to perform for an 

emergency use; or 

232.2 Operation of an emergency standby engine during maintenance of a primary 

motor. 

(Adopted August 1, 2001) 

9-8-233 Essential Public Service:

233.1 A sewage treatment facility, and associated collection system, which is 

publicly owned and operated; 

233.2 Water treatment and delivery operations; 

233.3 Public transit; 

233.4 Police or fire fighting facility; 

233.5 Airport runway lights; or 

233.6 Hospital or other medical emergency facility. 

(Adopted August 1, 2001) 

9-8-234 Best Available Control Technology (BACT): As defined in Regulation 2, Rule 2, 

Section 2-2-206 

(Adopted July 25, 2007) 

9-8-235 Dual Fuel Pilot Compression-Ignited Engine: Any dual-fueled engine that uses 

diesel fuel as a pilot ignition source at an annual average ratio of less then 5 parts 

diesel fuel to 100 parts total fuel on an energy equivalent basis. 

(Adopted July 25, 2007) 

9-8-236 Portable: Designed for and capable of being carried or moved from one location to 

another. Indications of portability include, but are not limited to, wheels, skids, 

carrying handles, dolly, trailer, or platform. 

(Adopted July 25, 2007) 

9-8-237 Unforeseeable: Not able to be reasonably anticipated and demonstrated by the 

owner or operator to the satisfaction of the APCO to have been beyond the 

reasonable control of the owner or operator. The enforcement of a contractual 

obligation the owner or operator has with a third party or any other party is 

foreseeable. 

(Adopted July 25, 2007) 
Bay Area Air Quality Management District July 25, 2007 

 9-8-5 

9-8-300 STANDARDS 

9-8-301 Emission Limits - Spark-Ignited Engines Powered by Fossil Derived Fuels:

Effective January 1, 1997, a person shall not operate a stationary internal 

combustion engine fired exclusively on fossil derived fuels, unless the following 

emission limits are met: 

301.1 Rich-Burn Engines: Nitrogen oxide (NOx) emissions shall not exceed 56 

ppmv as corrected to 15% oxygen, dry basis. Effective January 1, 2012, 

nitrogen oxide (NOx) emissions shall not exceed 25 ppmv as corrected to 

15% oxygen, dry basis. 

301.2 Lean-Burn Engines: Nitrogen oxide (NOx) emissions shall not exceed 140 

ppmv as corrected to 15% oxygen, dry basis. Effective January 1, 2012, 

nitrogen oxide (NOx) emissions shall not exceed 65 ppmv as corrected to 

15% oxygen, dry basis. 

301.3 Carbon monoxide (CO) emissions shall not exceed 2000 ppmv as corrected 

to 15% oxygen, dry basis. 

(Amended July 25, 2007) 

9-8-302 Emission Limits - Spark-Ignited Engines Powered by Waste Derived Fuels:

Effective January 1, 1997, a person shall not operate a spark-ignited stationary 

internal combustion engine fired on waste derived fuels or any combination of wasteand fossil-derived gaseous fuels and liquid fuels unless the following emission limits 

are met: 

302.1 Lean-Burn Engines: Nitrogen oxide (NOx) emissions shall not exceed 140 

ppmv as corrected to 15% oxygen, dry basis. Effective January 1, 2012, 

nitrogen oxide (NOx) emissions shall not exceed 70 ppmv as corrected to 

15% oxygen, dry basis. 

302.2 Rich-Burn Engines: Nitrogen oxide (NOx) emissions shall not exceed 210 

ppmv as corrected to 15% oxygen, dry basis. Effective January 1, 2012, 

nitrogen oxide (NOx) emissions shall not exceed 70 ppmv as corrected to 

15% oxygen, dry basis. 

302.3 Carbon monoxide (CO) emissions shall not exceed 2000 ppmv as corrected 

to 15% oxygen, dry basis. 

(Amended July 25, 2007) 

9-8-303 Emissions Limits – Delayed Compliance, Existing Spark-Ignited Engines, 51 to 

250 bhp or Model Year 1996 or Later: In lieu of compliance with Section 9-8-301 or 

302, a person may operate a stationary internal combustion, spark-ignited engine 

until January 1, 2016 provided: 

303.1 The brake horsepower rating of the engine is between 51 and 250 bhp or the 

model year of the engine is 1996 or later; 

303.2 The requirements of Section 9-8-402 are met; 

303.3 The engine complies with Best Available Control Technology requirements 

for a stationary internal combustion, spark-ignited engines no later than 

January 1, 2016. 

(Adopted July 25, 2007) 

9-8-304 Emission Limits – Compression-Ignited Engines: Effective January 1, 2012, a 

person shall not operate a stationary internal combustion compression-ignited engine 

unless one the applicable emission limit in ppmv corrected 15% oxygen, dry basis 

set forth below for NOx and CO is met: 

 Emission Standards

(ppmvd) 

Existing 

CompressionIgnited Engine

(bhp) NOx CO 

304.1 51 to 175 180 440 

304.2 Greater than 175 110 310 

(Adopted July 25, 2007) 
Bay Area Air Quality Management District July 25, 2007 

 9-8-6 

9-8-305 Emission Limits – Delayed Compliance, Existing Compression-Ignited Engines, 

Model Year 1996 or Later: In lieu of compliance with Section 9-8-304, a person 

may operate a stationary internal combustion compression-ignited engine of model 

year 1996 or later provided the requirements of Section 9-8-402 are met and one of 

the following conditions is met no later than January 1, 2016: 

305.1 The NOx and CO emissions shall not exceed Best Available Control 

Technology limits for a stationary internal combustion, compression-ignited 

engines, or 

305.2 the NOx emissions shall not exceed 22 ppmv corrected 15% oxygen, dry 

basis and the CO emissions shall not exceed 310 ppmv corrected 15% 

oxygen, dry basis. 

(Adopted July 25, 2007) 

9-8-306 Requirements for Dual Fuel Pilot Compression-Ignited Engines: Effective 

January 1, 2012, compression-ignited engines powered by diesel fuel and waste gas 

shall comply with spark-ignited waste-derived fuel emission limits in Section 9-8-302, 

provided the diesel fuel use does not exceed five percent on an energy basis of the 

total fuel consumption in any calendar year. 

(Adopted July 25, 2007) 

9-8-330 Emergency Standby Engines, Hours of Operation: A person may only operate an 

emergency standby engine under the following circumstances: 

330.1 For emergency use for an unlimited number of hours; and 

330.2 Until January 1, 2012, for reliability-related activities so long as total hours of 

operation for this purpose do not exceed 100 hours in a calendar year, or 

limitations contained in a District permit, whichever is lower. 

330.3 Effective January 1, 2012, for reliability-related activities so long as total 

hours of operation for this purpose do not exceed 50 hours in a calendar 

year, or limitations contained in a District permit, whichever is lower. Hours 

of operation for reliability-related activities may exceed these limits only as 

necessary to comply with testing requirements of National Fire Protection 

Association (NFPA) 25 – “Standard for the Inspection, Testing, and 

Maintenance of Water-Based Fire Protection Systems,” 1998 edition. 

(Adopted 8/1/01; Amended 7/25/07) 

9-8-331 Essential Public Service, Hours of Operation: An essential public service may 

only operate an emergency standby engine under the following circumstances: 

331.1 For emergency use for an unlimited number of hours; and 

331.2 Until January 1, 2012, for reliability-related activities so long as total hours of 

operation for this purpose do not exceed 200 hours per calendar year, or 

limitations contained in a District permit, whichever is lower. 

331.3 Effective January 1, 2012, for reliability-related activities so long as total 

hours of operation for this purpose do not exceed 100 hours in a calendar 

year, or limitations contained in a District permit, whichever is lower. 

(Adopted 8/1/01; Amended 7/25/07) 

9-8-400 ADMINISTRATIVE REQUIREMENTS 

9-8-401 Compliance Schedule: A person subject to the requirements of Section 9-8-301, 

302, 303, 304, 305 or 306 shall submit an application for any Authority to Construct, 

necessary to achieve compliance with such requirements no later than one year prior 

to the applicable compliance date listed in Section 9-8-301, 302, 303, 304, 305 or 

306. 

(Amended July 25, 2007) 

9-8-402 Reporting Requirements for Delayed Compliance: A person opting to comply with 

one of the delayed compliance options set forth in Section 9-8-303 or 305 shall notify 

the APCO in writing no later than January 1, 2012 that the owner or operator of a 

stationary engine has elected to comply with requirements of Section 9-8-303 in lieu 

of Section 9-8-301 or 302, or to comply with the requirements of Section 9-8-305 in 

lieu of Section 9-8-304. The report shall include the following information about the 

engine: source number; plant number, name, contact, phone number, address; and 

engine make, model, model year, and size. 
Bay Area Air Quality Management District July 25, 2007 

 9-8-7 

(Amended July 25, 2007) 

9-8-500 MONITORING AND RECORDS 

9-8-501 Initial Demonstration of Compliance: A person who must modify existing sources 

or install new control equipment shall conduct a District approved source test, 

pursuant to Sections 9-8-601 and 602 according to the schedule listed in the 

following table: 

Engines Operated to 

Comply with Section 

Date that the Initial 

Source Test Must Be 

Completed 

Date that the Initial 

Source Test Results Must 

Be Submitted to the 

District 

9-8-301, 302, 304 or 306 March 31, 2012 May 31, 2012 

9-8-303 or 305 March 31, 2016 May 31, 2016 

(Amended July 25, 2007) 

9-8-502 Recordkeeping: Any person who operates any engine subject to Section 9-8-300 

shall comply with the following recordkeeping requirements: 

502.1 Any person who operates any engine that is exempt from the requirements 

of Section 9-8-301, 302, 303, or 304 by Section 9-8-110 or 111 shall keep 

records of the number of hours the engine is fired on a monthly basis. Such 

records shall be retained for a minimum of 24 months from the date of entry 

and made available to District staff upon request. 

502.2 Any person who operates a dual fuel pilot compression-ignited engines in 

accordance to Sections 9-8-306 shall keep records of fuel usage for each 

type of fuel used for a minimum of 24 months and make them available to 

the District staff upon request. 

502.3 Any person who conducts either an initial demonstration of compliance 

according to Sections 9-8-501 and 9-8-601, 9-8-602, a quarterly 

demonstration of compliance according to Section 9-8-503, or an annual 

demonstration of compliance according to Sections 9-8-504 and 9-8-601 

shall keep records of the compliance demonstration for a minimum of 24 

months from the date of creation and made available to the District staff upon 

request. 

502.4 Any person who operates an engine pursuant to Section 9-8-305 shall keep 

records verifying the certification of that engine for a minimum of 24 months. 

(Amended July 25, 2007) 

9-8-503 Quarterly Demonstration of Compliance: Any person who must comply with 

Section 9-8-301, 302, 303, 304, 305, or 306 shall use a portable analyzer to take 

NOx and CO emission readings to verify compliance with the applicable emission 

limits in Sections 9-8-301 through 305 at least once during each calendar quarter in 

which a source test is not performed. All emission readings shall be taken with the 

engine operating either at conditions representative of normal operations or 

conditions specified in the permit-to-operate. The analyzer shall be calibrated, 

maintained, and operated in accordance with the manufacturer’s specifications and 

recommendations. NOx emission readings taken pursuant to this section shall be 

averaged over a consecutive 15-minute period. 

(Adopted July 25, 2007) 

9-8-530 Emergency Standby and Low Usage Engines, Monitoring and Recordkeeping:

Each emergency standby and low usage engine shall be equipped with a nonresettable totalizing meter that measures hours of operation or fuel usage. All 

records shall be kept for at least two years, and shall be available for inspection by 

District staff upon request. The operator shall keep a monthly log of usage that shall 

indicate the following: 

530.1 Hours of operation (total) 

530.2 Hours of operation (emergency) 

530.3 For each emergency, the nature of the emergency condition. 
Bay Area Air Quality Management District July 25, 2007 

 9-8-8 

For low usage engines, these provisions become effective on January 1, 2012. 

(Adopted 8/1/01; Amended 7/25/07) 

9-8-600 MANUAL OF PROCEDURES 

9-8-601 Determination of Nitrogen Oxides: The methods by which samples of exhaust 

gases are collected and analyzed to determine concentrations of nitrogen oxides are 

set forth in the District's Manual of Procedures, Volume IV, ST-13 A. 

(Amended July 25, 2007) 

9-8-602 Determination of Carbon Monoxide and Stack Gas Oxygen: The methods by 

which samples of exhaust gases are collected and analyzed to determine 

concentrations of carbon monoxide and stack gas oxygen are set forth in the 

District's Manual of Procedures, Volume IV, ST-6 (carbon monoxide) and ST-14 

(oxygen).