Rule 233-Stationary Internal Combustion Engines Page 1 of 8 

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RULE 233 -- STATIONARY INTERNAL COMBUSTION ENGINES 

(Adopted October 18, 1994)(Amended September 25, 2001, June 11,2002, Amended June 6 , 

2006) 

INDEX PAGE

233.1 GENERAL ................................................................................................................. 2

A. PURPOSE: ............................................................................................................... 2 

B. APPLICABILITY: .................................................................................................... 2 

C. EXEMPTIONS: ........................................................................................................ 2 

233.2 DEFINITIONS ........................................................................................................... 2

A. BASELINE EMISSION RATES: ............................................................................... 2 

B. DIESEL ENGINE: .................................................................................................... 2 

C. EMERGENCY STANDBY ENGINE:........................................................................ 3 

D. ENGINE RATING: ................................................................................................... 3 

E. LEAN-BURN ENGINE:............................................................................................ 3 

F. MAINTENANCE OPERATION:............................................................................... 3 

G. OUTPUT: ................................................................................................................. 3 

H. PERMITTED CAPACITY FACTOR: ........................................................................ 3 

I. RICH-BURN ENGINE:............................................................................................. 3 

J. PEAK LOAD:........................................................................................................... 3 

K. STATIONARY INTERNAL COMBUSTION ENGINE: ............................................. 3 

L. STOICHIOMETRIC AIR/FUEL RATIO:................................................................... 3 

M. WASTE GAS:....................................................................................................... 4 

233.3 STANDARDS............................................................................................................. 4

A. LIMITS: ................................................................................................................... 4 

B. ENGINE OPERATOR INSPECTION PLAN:............................................................. 4 

233.4 ADMINISTRATIVE REQUIREMENTS ................................................................... 5

A. REPORTING REQUIREMENTS:.............................................................................. 5 

B. SOURCE TESTING FREQUENCY:.......................................................................... 5 

233.5 MONITORING AND RECORDS .............................................................................. 6

A. RECORDS:............................................................................................................... 6 

B. TEST METHODS: .................................................................................................... 6 

C. EXEMPTION RECORDS: ........................................................................................ 7 

D. NONRESETTABLE METERS: ................................................................................. 7 

223.6 VIOLATIONS............................................................................................................ 7
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RULE 233 STATIONARY INTERNAL COMBUSTION ENGINES

233.1 GENERAL 

A. PURPOSE: 

The purpose of this rule is to limit the emission of oxides of nitrogen (NOx) and carbon 

monoxide (CO) from stationary internal combustion engines. 

B. APPLICABILITY: 

This rule applies to any stationary internal combustion engine rated at more than 50 brake 

horsepower, operated on any gaseous fuel or liquid fuel, including liquid petroleum gas 

(LPG), gasoline, or diesel fuel. This rule shall not apply to engines used directly and 

exclusively for agricultural operations necessary for the growing of crops or the raising of 

fowl and animals. 

C. EXEMPTIONS: 

The provisions of this rule, except for Section 233.5 C., and 233.5 D.2., shall not apply to the 

operation of stationary internal combustion engines used under the following conditions: 

1. Engines rated 50 brake horsepower or less, or 

2. Engines operated less than 200 hours per calendar year, or 

3. Emergency standby engines operated either during an emergency or maintenance 

operation. Maintenance operation is limited to 50 hours per calendar year, or 

4. Engines used in research or teaching programs, or 

5. Engine test stands used for evaluating engine performance, or 

6. Diesel engines with a permitted capacity factor of 15 percent or less, or 

7. Diesel engines used to power cranes and welding equipment. 

233.2 DEFINITIONS 

A. BASELINE EMISSION RATES: 

Emissions under normal operating conditions, prior to control, as determined by a source test 

conducted in accordance with Section 233.5 B., of this rule. 

B. DIESEL ENGINE: 

A compression ignited two or four stroke engine in which liquid fuel injected into the 

combustion chamber ignites when the air charge has been compressed to a temperature 

sufficiently high for autoignition. 
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C. EMERGENCY STANDBY ENGINE: 

An internal combustion engine used only as follows: 

1. When normal power line or natural gas service fails. 

2. For the emergency pumping of water for either fire protection or flood relief. An 

emergency standby engine may not be operated to supplement a primary power source 

when the load capacity or rating of the primary power source has either been reached or 

exceeded. 

D. ENGINE RATING: 

The output of an engine as determined by the engine manufacturer and listed on the 

nameplate of the engine, regardless of any derating. 

E. LEAN-BURN ENGINE: 

Any two or four-stroke spark-ignited engine that is not a rich-burn engine. 

F. MAINTENANCE OPERATION: 

The use of an emergency standby engine and fuel system during testing, repair and routine 

maintenance to verify its readiness for emergency standby use. 

G. OUTPUT: 

The shaft work output from an engine plus the energy reclaimed by any useful heat recovery 

system. 

H. PERMITTED CAPACITY FACTOR: 

The annual permitted fuel use divided by the manufacturer's specified maximum hourly fuel 

consumption times 8760 hours per year. 

I. RICH-BURN ENGINE: 

A two or four-stroke spark-ignited engine where the manufacturer's original recommended 

operating air/fuel ratio divided by the stoichiometric air/fuel ratio is less than or equal to 1.1. 

Engines using passive emission control technology (such as the use of pre-combustion 

chambers), and are listed as lean-burn engines on their Permit to Operate, shall be considered 

lean-burn engines. 

J. PEAK LOAD: 

Maximum instantaneous operating load. 

K. STATIONARY INTERNAL COMBUSTION ENGINE: 

Any internal combustion engine of the reciprocating type that is operated at a site for more 

than one year or is attached to a foundation, not including engines used for self-propulsion. 

L. STOICHIOMETRIC AIR/FUEL RATIO: 

The chemically correct air/fuel ratio where all fuel and all oxygen in the air/fuel mixture will 

be consumed. 
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M. WASTE GAS: 

Fuel gas produced at either waste water/sewage treatment facilities or landfills containing no 

more than 25 percent by volume supplemental gas. 

233.3 STANDARDS 

A. LIMITS: 

The owner or operator of an existing stationary internal combustion engine to which this rule 

is applicable shall limit the emissions from that engine to no more than the following: 

a. Rich-burn stationary internal combustion engine NOx emissions shall not exceed 25 

ppmv and CO emissions shall not exceed 2,000 ppmv. 

b. Lean-burn stationary internal combustion engine NOx emissions shall not exceed 65 

ppmv and CO emissions shall not exceed 2,000 ppmv. 

c. Diesel fired stationary internal combustion engine NOx emissions shall not exceed 

600 ppmv and CO emissions shall not exceed 2,000 ppmv. 

where: ppmv = parts per million volume at 

15% oxygen on a dry basis 

NOx = oxides of nitrogen 

CO = carbon monoxide 

B. ENGINE OPERATOR INSPECTION PLAN: 

The operator of an engine subject to the provisions of Sections 233.3 A., of this rule shall 

submit to the Air Pollution Control Officer an Engine Operator Inspection Plan. The plan 

shall be approved by the Air Pollution Control Officer in writing. The plan shall be updated 

after any change in operation. For new engines and modifications to existing engines, the 

plan shall be submitted to and approved by the Air Pollution Control Officer prior to issuance 

of the Permit to Operate. The operator may request a change to the plan at any time. The plan 

shall include the following: 

1. The manufacturer, model number, rated horsepower, and combustion method (i.e., richburn, lean-burn, or diesel) of the engine. 

2. A description of the NOx control system installed on the engine (if any), including type 

(e.g., nonselective catalyst, "clean-burn" combustion) and manufacturer, as well as a 

description of any ancillary equipment related to the control of emissions (e.g., automatic 

air/fuel ratio controller, fuel valves). 

3. The company identification and location of the engine by a schematic of the affected 

facilities. 

4. A specific emission inspection procedure to assure that the engine is operated in 

continual compliance with the provisions of this rule. The procedure shall include an 

inspection schedule. Inspections shall be conducted every quarter or after every 2,000 
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hours of engine operation. In no event shall the frequency of inspection be less than once 

per year. Testing results from individual engines in terms of rate brake horsepower, 

operational conditions, fuel used, and control method may satisfy these inspection 

requirements. Prior to implementation of testing, test plans shall be submitted to and 

approved in writing by the Air Pollution Control Officer. 

5. Each preventative or corrective maintenance procedure or practice that will be used to 

maintain the engine and NOx control system in continual compliance with the provisions 

of this rule. 

233.4 ADMINISTRATIVE REQUIREMENTS 

A. REPORTING REQUIREMENTS: 

Prior to renewal of any Permit to Operate, each operator subject to the provisions of this rule 

shall provide the Air Pollution Control Officer with data specifying the actual annual usage 

(e.g., fuel consumption, actual operating hours) of each affected engine. The data shall also 

include the engine manufacturer, model number, Permit number, and location of each 

affected engine, a summary of the maintenance and testing reports required in Section 233.3 

B., of this rule, and an annual emissions report. 

B. SOURCE TESTING FREQUENCY: 

1. If applicable to this rule, conduct screening analysis with the use of a portable NOx 

analyzer 

a. During any quarter in which a source test is not performed, a portable NOx analyzer 

shall be used to take NOx emission readings to verify compliance with the emission 

limits specified in section 233.3 A. 

b. All emission readings shall be taken at an engine’s actual peak load and under the 

engine’s typical duty cycle. 

c. The analyzer shall be calibrated, maintained and operated in accordance with the 

manufacturer’s specifications and recommendations or a protocol approved by the 

Air Pollution Control Officer. 

d. In conducting quarterly screenings with a portable analyzer, an instrument reading in 

excess of the emission compliance values shall not be considered a violation, so long 

as the engine is brought into compliance within 15 days of the initial out of 

compliance reading. All NOx readings shall be reported to the Air Pollution Control 

Officer (APCO) or the APCO’s designee in a manner specified by the Air Pollution 

Control Officer. 

2. If applicable, emission source testing for Stationary Internal Combustion Engines. 

a. The owner of operator shall arrange for and assure that an emissions source test is 

performed on each stationary internal combustion engine at least once every 24 

months. 
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b. All emission readings shall be taken at an engine’s actual peak load and under the 

engine’s typical duty cycle. 

c. Prior to any source test required by this rule, a source test protocol shall be 

prepared and submitted to the Air Pollution Control Officer. In addition to other 

information, the source test protocol shall describe which critical parameters will 

be established and incorporated into the Engine Operator Inspection Plan described 

in section 233.3 B. The source test protocol shall be approved by the Air Pollution 

Control Officer prior to any testing. NOx and CO concentrations shall be reported 

in ppmv, corrected to 15 percent oxygen. For engines using exhaust controls, NOx 

shall also be reported as a percent reduction across the control device. All source 

test reports shall be submitted to the Air Pollution Control Officer or his designee. 

233.5 MONITORING AND RECORDS 

A. RECORDS: 

The operator of any engine subject to the provisions of Section 233.3 A., of this rule shall 

maintain an inspection log containing at a minimum, the following data: 

1. Identification and location of each engine subject to the provisions of this rule; 

2. Date and results of each emission inspection; 

3. A summary of any corrective emissions maintenance taken to ensure compliance with the 

emissions limits; and 

4. Any additional information required in the Engine Operator Inspection Plan. 

The operator shall maintain the inspection log for a period of two years after the date of each 

entry. The log shall be available for inspection by the Air Pollution Control Officer upon 

request. 

B. TEST METHODS: 

1. Oxides of nitrogen emissions for compliance source tests shall be determined in 

accordance with EPA Method 7E or CARB Method 100. 

2. Carbon Monoxide emissions for compliance source tests shall be determined in 

accordance with EPA Method 10 or CARB Method 100. 

3. Oxygen content for compliance source tests shall be determined in accordance with EPA 

Method 3A or CARB Method 100. 

4. Screening analyses shall be performed by using a portable analyzer approved in writing 

by the Air Pollution Control Officer. 

5. NOx emission limitations specified in Sections 233.3 A.1., of this rule shall be expressed 

as nitrogen dioxide. All ppmv emission limitations are referenced at 15 percent volume 

stack gas oxygen measured on a dry basis. Source test data point intervals shall be no 

greater than 5 minutes and data points shall be averaged over 15 consecutive minutes. 
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6. The heating value of fuel oil shall be determined in accordance with ASTM Method 

D240-87. The heating value of gaseous fuels shall be determined in accordance with 

ASTM Method D1826-77. 

C. EXEMPTION RECORDS: 

1. Any owner or operator claiming an exemption under Section 233.1 C., of this rule shall 

submit support documentation identifying reasons for the exemption. Such 

documentation shall contain a list that provides the following for each engine: 

a. Permit to Operate number; 

b. Engine manufacturer; 

c. Model designation; 

d. Rated brake horsepower; 

e. Type of fuel and type of ignition. 

2. In addition to the requirements specified in Section 233.5 C.1., of this rule, an owner or 

operator claiming an exemption under Sections 233.1 C.2., and 233.1 C.3., of this rule 

shall maintain a log of operating hours for each engine. 

3. Exemption records specified in Sections 233.5 C.1., and 233.5 C.2., of this rule shall be 

retained for two years and be made available to the Air Pollution Control Officer upon 

request. 

D. NONRESETTABLE METERS: 

1. Fuel Meter 

All engines subject to Section 233.3 A. of this rule, shall have installed a nonresettable 

fuel meter. 

2. Elapsed Operating Time Meter 

All engines subject to this rule, emergency standby engines, and engines operated less 

than 200 hours per calendar year shall have installed a nonresettable elapsed operating 

time meter. 

223.6 VIOLATIONS 

1. Failure to comply with any provisions of this rule shall constitute a violation of this rule. 

2. It is the responsibility of the engine operator to demonstrate to the satisfaction of the Air 

Pollution Control Officer that an engine subject to the provisions of this rule is being 

operated in continuous compliance with all applicable provisions of this rule. 

3. An engine shall be in violation if it is operated out of compliance with the operating 

parameters of an approved Engine Operator Inspection Plan. However, if data from a 
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source test of the engine operating under identical conditions indicates that the engine is 

in compliance with the requirements of this rule, then a violation will - not have occurred. 

The source test shall be conducted at the engine operator's expense. The Engine Operator 

Inspection Plan shall be amended to reflect the information from this source test.