Alternative Emission Limit for Emissions From

Stationary Internal Combustion Engines

For stationary internal combustion engines, emissions shall not

exceed an emission limit as determined by the following equation:


For rich-burn engines, the STANDARD is 50 ppm NOx, 4500 ppm CO,

and 250 ppm ROC as corrected to 15% oxygen at an engine STANDARD


For lean-burn engines, the STANDARD is 125 ppm NOx, 4500 ppm CO,

and 750 ppm ROC as corrected to 15% oxygen at an engine STANDARD


UNIT EFFICIENCY = The output from an engine divided by the energy

input (as determined by a fuel measuring device accurate to ±5%

and based on the higher heating value of the fuel). Any engine

which has a tested efficiency greater than 30% will be allowed to

use the demonstrated efficiency as the UNIT EFFICIENCY. Any

engine with an efficiency lower than 30% is allowed a 30% UNIT

EFFICIENCY for the purpose of this calculation.

The volume concentration (ppm) of the oxides of nitrogen (NOx)

shall be calculated as nitrogen dioxide. All measurements shall

be corrected to 15% oxygen (02) on a dry basis as follows:

20.9% - 15%

PPM (15% O2) = PPM (measured) x ____________________

20.9% - %O2 (measured)


Modified EPA Method 20

For the purpose of this rule, the following modifications shall

be applied to EPA Reference Method 20 as published in the Federal

Register on September 10, 1979.

1.General Note - All references to SO2 or sulfur measurement

shall be deleted.

2.Section 4.1.4 - The NOx to NO converter as shown in Figure

20.1 is normally integrated into the NOx analyzer. In

addition, deletion of the converter shall not be an option.

3.Section 4.3 - Calibration gases shall be at 0, 50 percent,

and 90 percent of full scale. The full scale value shall be

selected so that the measured value is approximately 50

percent of scale.

4.Section 6.1.2 - Delete all references to a preliminary O2

traverse; however, O2 shall be measured continuously during

the test.

5.Section - A single test point shall be used for

exhaust ducts up to 24 inches in diameter. A minimum of 8

points shall be required for ducts equal to or greater than

24 inches in diameter.

6.Section 6.2 - Testing shall be done over the permitted

operating load conditions of the engine. To determine

compliance initially, the test period shall be a minimum of

fifteen minutes per load condition. However, if the source

is not in compliance after the initial fifteen minutes, the

test shall be continued for at least one hour and forty-five

minutes. The stack shall be traversed initially to

determine the degree of stratification in the stack.

Sampling time at each traverse point shall be a minimum of

two minutes plus system response time. The remainder of the

test period shall be with the probe inlet at the average