1146.1-1

(Adopted October 5, 1990)(Amended July 10, 1992)(Amended May 13, 1994)

(September 5, 2008)

RULE 1146.1 EMISSIONS OF OXIDES OF NITROGEN FROM SMALL 

INDUSTRIAL, INSTITUTIONAL, AND COMMERCIAL 

BOILERS, STEAM GENERATORS, AND PROCESS 

HEATERS

(a) Applicability

This rule applies to boilers, steam generators, and process heaters that are greater 

than 2 million Btu per hour and less than 5 million Btu per hour rated heat input 

capacity used in any industrial, institutional, or commercial operation.

(b) Definitions

(1) ANNUAL HEAT INPUT means the actual amount of heat released by 

fuels burned in a unit during a calendar year, based on the fuel's higher 

heating value.

(2) ATMOSPHERIC UNIT means any natural gas fired unit with a non-sealed 

combustion chamber in which natural draft is used to exhaust combustion 

gases.

(3) BOILER OR STEAM GENERATOR means any combustion equipment 

fired with liquid and/or gaseous (including landfill and digester gas) and/or 

solid fossil fuel, used to produce steam or to heat water, and that is not 

used exclusively to produce electricity for sale. Boiler or Steam Generator 

does not include any waste heat recovery boiler that is used to recover 

sensible heat from the exhaust of a combustion turbine or any unfired 

waste heat recovery boiler that is used to recover sensible heat from the 

exhaust of any combustion equipment.

(4) BTU means British thermal unit or units.

(5) HEALTH FACILITY has the same meaning as defined in Section 1250 of 

the California Health and Safety Code.

(6) NOx EMISSIONS means the sum of nitric oxide and nitrogen dioxide in 

the flue gas, collectively expressed as nitrogen dioxide.

(7) PROCESS HEATER means any combustion equipment fired with liquid 

and/or gaseous (including landfill and digester gas) and/or solid fossil fuel 

and which transfers heat from combustion gases to water or process 

streams. Process Heater does not include any kiln or oven used for drying, 

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-2

curing, baking, cooking, calcining, or vitrifying; or any unfired waste heat 

recovery heater that is used to recover sensible heat from the exhaust of 

any combustion equipment.

(8) RATED HEAT INPUT CAPACITY means the heat input capacity 

specified on the nameplate of the combustion unit. If the combustion unit 

has been altered or modified such that its maximum heat input is different 

than the heat input capacity specified on the nameplate, the new maximum 

heat input shall be considered as the rated heat input capacity.

(9) SCHOOL means any public or private school, including juvenile detention 

facilities with classrooms, used for purposes of the education of more than 

12 children at the school, including in kindergarten and grades 1 to 12, 

inclusive, but does not include any private school in which education is 

primarily conducted in private homes. The term includes any building or 

structure, playground, athletic field, or other area of school property, but 

does not include unimproved school property.

(10) THERM means 100,000 Btu.

(11) THERMAL FLUID HEATER means a PROCESS HEATER in which a 

process is heated indirectly by a heated fluid other than water.

(12) UNIT means any boiler, steam generator, or process heater as defined in 

paragraph (b)(3) or (b)(7).

(c) Requirements

(1) On or after September 5, 2008, the owner or operator of any unit subject to 

subdivision (a) shall operate such unit so that it discharges into the 

atmosphere no more than 30 ppm of NOx emissions or for natural gas 

fired units 0.037 pound NOx per million Btu of heat input, as specified in 

the permit to operate.

(2) An owner or operator of any unit subject to subdivision (a) must select to 

comply with one of the following NOx emission limits specified in Table 1146.1-1 and 

apply for a permit to construct to operate such unit in compliance with the selected 

emission limit and the corresponding permit application and full compliance dates.Table 

1146.1-1

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Deleted: (b)

Deleted: Applicability¶

Deleted: This rule applies to boilers, steam generators, and 

process heaters that are greater than 2 million Btu per hour and 

less than 5 million Btu per hour rated heat input capacity used 

in any industrial, institutional, or commercial operation.¶

Deleted: T

Deleted: b

Deleted: and no more than 400 ppm of carbon monoxide. 

For each unit, a selection must be indicated in the application 

for permit to construct and operate between the ppm NOxor 

pounds of NOxper million BTU heat input compliance option

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-3

(3) For dual fuel co-fired combustion units a weighted average limit 

calculated by Equation 1146.1-1 may be used provided a totalizing fuel 

flow meter is installed pursuant to paragraph (c)(7), for units burning a 

combination of both fuels. 

Weighted Limit = ______________________ Equation 1146.1-1

 QA + QB

Where:

CLA = compliance limit for fuel A

CLB = compliance limit for fuel B

QA = heat input from fuel A

QB = heat input from fuel B

(4) The owner or operator of any unit(s) with a heat input capacity greater than 

or equal to 2 million Btu per hour shall not discharge into the atmosphere 

carbon monoxide (CO) emissions in excess of 400 ppm or for natural gas 

fired units 0.30 lbs/106 Btu.

(5) In lieu of complying with the applicable emission limits specified in 

paragraph (c)(1) or (c)(2) any unit(s) subject to subdivision (a) in operation 

prior to September 5, 2008, and with an annual heat input of less than or 

equal to 18,000 therms per calendar year, shall:

Category Limit

Submit Application 

for Permit to

Construct on or 

before

Unit Shall be in Full 

Compliance on or 

before

Any Units Fired on Landfill Gas 25 ppm January 1, 2014 January 1, 2015

Any Units Fired on Digester Gas 15 ppm January 1, 2014 January 1, 2015

Atmospheric Units 12 ppm or

0.015 lbs/106 Btu

January 1, 2013 January 1, 2014

Any Units Fired on Natural Gas, 

Excluding Units Located at 

Schools and Universities,

Atmospheric Units, and Thermal 

Fluid Heaters 9 ppm or

January 1, 2011 January 1, 2012

Any Units Fired on Natural Gas 

Located at Schools and 

Universities, Excluding

Atmospheric Units, and Thermal 

Fluid Heaters

0.011 lbs/106 Btu January 1, 2013 January 1, 2014

(CLA x QA) + (CLB x QB)

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-4

(A) be operated in a manner that maintains stack-gas oxygen 

concentrations at less than or equal to 3 percent on a dry basis for 

any 15-consecutive-minute averaging period; or

(B) be tuned at least twice per year, (at intervals from four to eight 

months apart) in accordance with the procedure described in 

Attachment 1 or the unit manufacturer's specified tuneup 

procedure. If a different tuneup procedure from that described in 

attachment 1 is used then a copy of this procedure shall be kept on 

site. The operator of any unit(s) selecting the tune-up option shall 

maintain records for a rolling of twenty four month period 

verifying that the required tune-ups have been performed. If the 

unit does not operate throughout a continuous six-month period 

within 12 month period, only one tuneup is required for the twelve 

month period that includes the entire period of non-operation . For 

this case, the tune-up shall be conducted within 30 days of start-up. 

No tune-up is required during a rolling twelve month period for 

any unit that is not operated during that rolling twelve month 

period; this unit may be test fired to verify availability of the unit 

for its intended use but once test firing is completed it shall be 

shutdown. Records of test firings shall be maintained for a rolling 

twenty four month period, and shall be made accessible upon 

request from an authorized District representative upon request

.

(6) An owner or operator that has installed or modified a natural gas fired unit 

prior to September 5, 2008 complying with the applicable BACT emission 

limit of 12 ppm or less of NOx may defer compliance with paragraph 

(c)(2) until the unit’s burner(s) replacement.

(7) Any owner or operator who chooses the pound per million Btu of heat 

input compliance option in paragraph (c)(1), (c)(2), or (c)(4) for natural 

gas fired units or chooses the weighted average emission limit using 

Equation 1146.1-1 under paragraph (c)(3) shall install a non-resettable, 

totalizing fuel meter for each fuel used on an individual unit basis, as 

approved by the Executive Officer.

(8) On or after January 1, 2015, an owner operator of any landfill or digester 

gas (biogas) unit co-fired with natural gas shall not operate the unit in a 

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Deleted: The ow.er or operator of any unit(s) who chooses to 

comply with subparagraph (c)(2)(B) shall maintain a record for 

a period of two years verifying that the tuneup has been 

performed.

Deleted: calendar year 

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Deleted: ; or¶

Deleted: (C)

Deleted: meet the emission limits specified in paragraph 

(c)(1)

Deleted: (3)

Deleted: The owner or operator of any unit(s) subject to 

paragraph (c)(2) shall submit and have approved by the 

Executive Officer, a compliance plan that demonstrates 

compliance with paragraph (c)(2). Such plan shall contain:¶

Deleted: (A)

Deleted: A list of permits of all units with the rated heat input 

capacity, anticipated annual heat input; and¶

Deleted: (B)

Deleted: For each unit listed, a selection of one of the three 

options specified in paragraph (c)(2) to achieve compliance 

with this rule; and¶

Deleted: (C)

Deleted: Non-resettable, totalizing fuel meter(s) 

specifications; date of 

Deleted: installation; and recorded fuel usage since 

installation.

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-5

manner that exceeds the applicable landfill or digester gas emission 

concentration limits specified in paragraph (c)(2), provided that the facility 

monthly average biogas usage by the biogas units is 90% or more, based 

on the higher heating value of the fuels used.

(A) The Executive Officer may approve the burning of more than 

10% up to:

(i) 25% natural gas in a biogas fired unit at the 15 ppm 

(digester gas) or 25 ppm (landfill gas) NOx level, when it 

is necessary, if the only alternative to limiting natural gas 

to 10% would be shutting down the unit and flaring more 

biogas.

(ii) 50% natural gas in a digester gas-fired unit at the 15 ppm 

NOx level, when it is necessary as specified in clause (c) 

(8)(A)(i) and for units installed on or after September 5, 

2008 provided the unit has demonstrated compliance with 

the NOx limits in paragraph (c)(2) applicable to units 

fired exclusively on natural gas.

For units subject to this subparagraph, the percent natural gas 

usage shall be based on the facility monthly average biogas 

usage by the biogas units and the higher heating value of the 

fuels used.

(B) Any biogas-fired unit burning more than the approved percent 

natural gas as determined under subparagraph (c)(8)(A) shall 

comply with the weighted average NOx limit specified in 

paragraph (c)(3).

(d) Compliance Determination

(1) Owners or operators of any units shall have the option of complying with 

either the pound per million Btu of heat input or parts per million emission 

limits specified in paragraph (c)(1), (c)(2), (c)(3), or (c)(4).

(2) All emission determinations shall be made in the as-found operating 

condition, except no compliance determination shall be established during 

unit start up, shutdown, or under breakdown conditions. Start up or 

shutdown intervals shall not last longer than is necessary to reach stable 

temperatures. In no case shall the start up or shutdown interval last longer 

than six hours or the time specified in the permit to operate, whichever is 

less. Start-ups and shutdowns shall not last longer than is necessary to 

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-6

reach stable conditions. An compliance determination as specified in 

paragraph (d)(6) shall be conducted at least 250 operating hours, or at least 

thirty days subsequent to the tuning or servicing of any unit, unless it is an 

unscheduled repair.

(3) All parts per million emission limits specified in subdivision (c) are 

referenced at 3 percent volume stack-gas oxygen on a dry basis averaged 

over a period of 15 consecutive minutes.

(4) Compliance with the NOx and CO emission requirements of paragraphs

(c)(1) through (c)(4) and the stack-gas oxygen concentration requirement 

of subparagraph (c)(5)(A) shall be determined using a District approved 

contractor under the Laboratory Approval Program according to the 

following procedures:

(A) District Source Test Method 100.1 - Instrumental Analyzer 

Procedures for Continuous Gaseous Emission Sampling (March 

1989), or

(B) District Source Test Method 7.1 - Determination of Nitrogen Oxide 

Emissions from Stationary Sources (March 1989) and Method 10.1 

- Carbon Monoxide and Carbon Dioxide by Gas 

Chromatograph/Non-Dispersive Infrared Detector (GC/NDIR) -

Oxygen by Gas Chromatograph-Thermal Conductivity (GC/TCD) 

(March 1989), or

(C) United States Environmental Protection Agency Conditional Test 

Method CTM-030, Determination of Nitrogen Oxides, Carbon 

Monoxide, and Oxygen Emissions from Natural Gas-Fired Engines, 

Boilers and Process Heaters Using Portable Analyzers; or

(D) ASTM D6522-00(2005) Standard Test Method for Determination 

of Nitrogen Oxides, Carbon Monoxide, and Oxygen Concentrations 

in Emissions from Natural Gas-Fired Reciprocating Engines, 

Combustion Turbines, Boilers, and Process Heaters Using Portable 

Analyzers

(E) any other test method determined to be alternative and approved 

before the test in writing by the Executive Officers of the District 

and the California Air Resources Board and the Regional 

Administrator of the United States Environmental Protection 

Agency, Region IX.

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-7

Records of all source tests shall be maintained for a period of two years 

(five years for Title V facilities) and shall be made available to District 

personnel upon request. Emissions determined to exceed any limits 

established by this rule through the use of any of the above-referenced test 

methods shall constitute a violation of this rule.

(5) For any owner or operator who chooses the pounds of per million Btu of 

heat input compliance option of paragraph (c)(1), (c)(2), or (c)(4) for 

natural gas fired units, NOx emissions in pounds per million Btu of heat 

input shall be calculated using the procedures in 40 CFR Part 60, 

Appendix A, Method 19, Sections 2 and 3 and CO emissions in pounds 

per million Btu of heat input shall be calculated according to the Protocol 

for the Periodic Monitoring of Nitrogen Oxides, Carbon Monoxide, and 

Oxygen from Units Subject to South Coast Air Quality Management 

District Rules 1146 and 1146.1.

(6) Compliance determination with the NOx emission requirements specified 

in paragraph (d)(4) shall be conducted once every five years.

(7) Any owner or operator of units subject to this rule shall check NOx

emissions with a portable NOx, CO and oxygen analyzer according to the 

Protocol for the Periodic Monitoring of Nitrogen Oxides, Carbon 

Monoxide, and Oxygen from Units Subject to South Coast Air Quality 

Management District Rules 1146 and 1146.1 according to the following 

schedule:

(A) On or after July 1, 2009, the owner or operator of units subject to 

paragraphs (c)(1) through (c)(4) shall check NOx emissions at least 

quarterly or every 2,000 unit operating hours, whichever occurs 

later. If a unit is in compliance for four consecutive required 

emission checks, without any adjustments to the oxygen sensor set 

points, then the unit may be checked semi-annually or every 4,000 

unit operating hours, whichever occurs later, until there is an

emission check indicating noncompliance.

(B) On or after January 1, 2015 or during burner replacement, 

whichever occurs later, units subject to paragraph (c)(5) shall 

check NOx emissions according to the tune-up schedule specified 

in subparagraph (c)(5)(B).

(C) Records of all monitoring data required under subparagraphs 

(d)(7)(A) and (d)(7)(B) shall be maintained for a rolling twelve 

Deleted: NOx

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-8

month period of two years (five years for Title V facilities) and 

shall be made available to District personnel upon request. An 

owner or operator shall not be considered in violation of the 

emissions limits of this rule or in permit conditions if the owner or 

operator complies with requirements specified in paragraph (d)(9). 

Any emission check conducted by District staff that finds excess 

emissions is a violation.

(D) The portable analyzer tests required under subparagraphs (d)(7)(A) 

and (d)(7)(B) shall only be conducted by a person who has 

completed an appropriate District-approved training program in the 

operation of portable analyzers and has received a certification 

issued by the District.

(8) An owner or operator shall opt to comply with the requirements as applied 

to CO emissions specified in paragraph (d)(6) or (d)(7).

(9) A source test specified under paragraph (d)(6) or an emission check 

conducted under the requirements specified in paragraph (d)(7) that finds 

emissions in excess of those allowed by this rule or a permit condition

shall not constitute a violation of this rule if the owner or operator corrects

the problem and demonstrate compliance with another source test or 

emission check within 72 hours from the time the owner or operator knew 

of excess emissions, or reasonably should have known, or shut down the 

unit by the end of an operating cycle, whichever is sooner.

(10) An owner or operator may opt to lower the unit’s rated heat input capacity. 

The lowered rated heat input capacity shall not be less than 2 million Btu 

per hour and shall be based on manufacturer’s identification or rating plate 

or permit condition.

(e) Compliance Schedule

(1) Owners or operators of units shall comply with the applicable schedule 

specified in paragraphs (c)(1) and (c)(2).

(2) On or after January 1, 2015 or during burner replacement, whichever is 

later, no person shall operate in the District any unit subject to paragraph 

(c)(5) which does not meet the emissions limits specified in paragraph 

(c)(1).

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Deleted: The owner or operator of units subject to this rule 

shall meet the following increments of progress:

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Deleted: o

Deleted: subject to

Deleted: shall:

Deleted: (A)

Deleted: By January 1, 1993, submit required applications for 

permits to construct and operate, and¶

(B)

Deleted: By July 1, 1994, demonstrate compliance with 

paragraph (c)(1).¶

For owners or operators of units subject to paragraph (c)(2) 

shall:¶

(A) By January 1, 1993, submit a plan pursuant to paragraph 

(c)(3), and¶

(B) By December 31, 1993, demonstrate compliance with 

paragraph (c)(2).

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-9

(3) If any unit subject to paragraph (c)(5) exceeds 18,000 therms of annual 

heat input from all fuels used in any twelve month period, the owners or 

operators shall:

(A) within 4 months after exceeding 18,000 therms of heat input in any 

twelve month period, submit required applications for permits to 

construct and operate; and

(B) within 18 months after exceeding 18,000 therms of heat input in 

any twelve month period, demonstrate and maintain compliance 

with all applicable requirements specified in paragraphs (c)(1) 

through (c)(4) for the life of the unit.

(4) The Executive Officer shall grant a time extension to the full compliance 

date with the applicable NOx compliance limits for any natural gas fired 

units specified in paragraph (c)(2) for any health facility as defined in 

Section 1250 of the California Health and Safety Code that can 

demonstrate that the Office of Statewide Health Planning and 

Development has approved an extension of time to comply with seismic

safety requirements pursuant to Health and Safety Code Sections 130060 

and 130061.5. The extension of time granted by the Executive Officer 

shall be consistent with the time extension granted pursuant to Health and 

Safety Code Section 130060 but not to exceed January 1, 2015 and shall 

be consistent with the time extension granted pursuant to Health and 

Safety Code Section 130061.5 but not to exceed January 1, 2020. Those 

health facilities granted a time extension shall submit a compliance plan to 

the Executive Officer on or before January 1, 2010.

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Deleted: (f)

Deleted: Exemption

Deleted: The provisions of paragraph (c)(1) shall 

not apply provided the owner or operator:¶

Deleted: (1)

Deleted: Installs by January 1, 1992, or at the time 

the permit to construct for the unit is issued, a nonresettable, totalizing fuel meter for each fuel that 

demonstrates that the unit(s) operate with an annual 

heat input at or below 18,000 therms per calendar 

year; and¶

Deleted: (2)

Deleted: Has available for inspection by the 

Executive Officer by February 1 of each year, 

records listing cumulative annual usage of each fuel 

for the preceding calendar year. Records shall be 

maintained and made accessible to the Executive 

Officer or authorized District representative for a 

period of two years; and¶

Deleted: (3)

Deleted: Demonstrates compliance with the 

requirements specified in subparagraphs (c)(2)(A) or 

(c)(2)(B), and (c)(3).

Deleted: (g)

Deleted: Loss of Exemption¶

Deleted: If any unit subject to a compliance plan 

submitted pursuant to paragraph (c)(3) exceeds 

18,000 therms of annual heat input in any calendar 

year after 1992, the owners or operators shall:¶

Deleted: (1)

Deleted: Within 4 months after the end of the 

calendar year during which the unit exceeded 18,000 

therms of annual heat input, submit required 

applications for permits to construct and operate; 

and¶

Deleted: (2)

Deleted: Within 18 months after the end of the 

calendar year during which the unit exceeded 18,000 

therms of annual heat input, demonstrate and 

maintain compliance with paragraph (c)(1) for the 

life of the unit; and¶

Deleted: (3)

Deleted: Maintain compliance with requirements 

of paragraph (c)(2) until compliance with paragraph 

(c)(1).¶
Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-10

ATTACHMENT 1

A. Equipment Tuning Procedure1 for Forced-Draft Boilers, Steam Generators, and 

Process Heaters

Nothing in this Equipment Tuning Procedure shall be construed to require any act or 

omission that would result in unsafe conditions or would be in violation of any regulation or 

requirement established by Factory Mutual, Industrial Risk Insurers, National Fire Prevention 

Association, the California Department of Industrial Relations (Occupational Safety and 

Health Division), the Federal Occupational Safety and Health Administration, or other 

relevant regulations and requirements.

1. Operate the unit at the firing rate most typical of normal operation. If the unit 

experiences significant load variations during normal operation, operate it at its 

average firing rate.

2. At this firing rate, record stack gas temperature, oxygen concentration, and CO 

concentration (for gaseous fuels) or smoke-spot number2 (for liquid fuels), and 

observe flame conditions after unit operation stabilizes at the firing rate selected. If 

the excess oxygen in the stack gas is at the lower end of the range of typical minimum 

values3, and if CO emissions are low and there is not smoke, the unit is probably 

operating at near optimum efficiency - at this particular firing rate. 

3. Increase combustion air flow to the furnace until stack gas oxygen levels increase by 

one to two percent over the level measured in Step 2. As in Step 2, record the stack 

gas temperature, CO concentration (for gaseous fuels) or smoke-spot number (for 

liquid fuels), and observe flame conditions for these higher oxygen levels after boiler 

operation stabilizes.

However, complete the remaining portion of this procedure to determine whether still lower 

oxygen levels are practical.

 

1This tuning procedure is based on a tune-up procedure developed by KVB, Inc. for the United States EPA.

2The smoke-spot number can be determined with ASTM Test Method D-2156 or with the Bacharach method. 

ASTM Test Method D-2156 is included in a tuneup kit that can be purchased from the Bacharach Company.

3Typical minimum oxygen levels for boilers at high firing rates are:

1. For natural gas: 0.5% - 3%

2. For liquid fuels: 2% - 4%
Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-11

4. Decrease combustion air flow until the stack gas oxygen concentration is at the level 

measured in Step 2. From this level gradually reduce the combustion air flow, in 

small increments. After each increment, record the stack gas temperature, oxygen 

concentration, CO concentration (for gaseous fuels) and smoke-spot number (for 

liquid fuels). Also observe the flame and record any changes in its condition.

5. Continue to reduce combustion air flow stepwise, until one of these limits is reached:

a. Unacceptable flame conditions - such as flame impingement on furnace walls 

or burner parts, excessive flame carryover, or flame instability.

b. Stack gas CO concentrations greater than 400 ppm.

c. Smoking at the stack.

d. Equipment-related limitations - such as low windbox/furnace pressure 

differential, built in air-flow limits, etc.

6. Develop an O2/CO curve (for gaseous fuels) or O2/smoke curve (for liquid fuels) 

similar to those shown in Figures 1 and 2 using the excess oxygen and CO or smokespot number data obtained at each combustion air flow setting.

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-12

7. From the curves prepared in Step 6, find the stack gas oxygen levels where the CO 

emissions or smoke-spot number equal the following values:

Fuel Measurement Value

Gaseous CO Emissions 400 ppm

#1 and #2 oils smoke-spot number number 1

#4 oil smoke-spot number number 2

#5 oil smoke-spot number number 3

Other oils smoke-spot number number 4

The above conditions are referred to as the CO or smoke thresholds, or as the 

minimum excess oxygen level.

Compare this minimum value of excess oxygen to the expected value provided by the 

combustion unit manufacturer. If the minimum level found is substantially higher 

than the value provided by the combustion unit manufacturer, burner adjustments can 

probably be made to improve fuel and air mixing, thereby allowing operation with 

less air.

8. Add 0.5 to 2.0 percent O2 to the minimum excess oxygen level found in Step 7 and 

reset burner controls to operate automatically at this higher stack gas oxygen level. 

This margin above the minimum oxygen level accounts for fuel variations, variations 

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Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-13

in atmospheric conditions, load changes, and nonrepeatability or play in automatic 

controls.

9. If the load of the combustion unit varies significantly during normal operation, repeat 

Steps 1-8 for firing rates that represent the upper and lower limits of the range of the 

load. Because control adjustments at one firing rate may affect conditions at other 

firing rates, it may not be possible to establish the optimum excess oxygen level at all 

firing rates. If this is the case, choose the burner control settings that give best 

performance over the range of firing rates. If one firing rate predominates, settings 

should optimize conditions at that rate.

10. Verify that the new settings can accommodate the sudden load changes that may 

occur in daily operation without adverse effects. Do this by increasing and decreasing 

load rapidly while observing the flame and stack. If any of the conditions in Step 5 

result, reset the combustion controls to provide a slightly higher level of excess 

oxygen at the affected firing rates. Next, verify these new settings in a similar 

fashion. Then make sure that the final control settings are recorded at steady-state 

operating conditions for future reference.

11. When the above checks and adjustments have been made, record data and attach 

combustion analysis data to boiler, steam generator, or heater records indicating name 

and signature of person, title, and date the tuneup was performed.

B. Equipment Tuning Procedure for Natural Draft-Fired Boilers, Steam 

Generators, and Process Heaters.

Nothing in this Equipment Tuning Procedure shall be construed to require any act or 

omission that would result in unsafe conditions or would be in violation of any regulation or 

requirement established by Factory Mutual, Industrial Risk Insurers, National Fire Prevention 

Association, the California Department of Industrial Relations (Occupational Safety and 

Health Division), the Federal Occupational Safety and Health Administration, or other 

relevant codes, regulations, and equipment manufacturers specifications and operating 

manuals.

Should a different tuning procedure be used, a copy of this procedure should be kept with the 

unit records for two years and made available to the District personnel on request.
Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-14

1. PRELIMINARY ANALYSIS

a. CHECK THE OPERATING PRESSURE OR TEMPERATURE.

Operate the boiler, steam generator, or heater at the lowest acceptable pressure 

or temperature that will satisfy the load demand. This will minimize heat and 

radiation losses. Determine the pressure or temperature that will be used as a 

basis for comparative combustion analysis before and after tuneup.

b. CHECK OPERATING HOURS.

Plan the workload so that the boiler, steam generator, or process heater 

operates only the minimum hours and days necessary to perform the work 

required. Fewer operating hours will reduce fuel use and emissions. For units 

requiring a tuneup to comply with the rule, a totalizing non-resettable fuel 

meter will be required for each fuel used and for each boiler, steam generator, 

and heater to prove fuel consumption is less than the heat input limit in therms 

per year specified in the rule.

c. CHECK AIR SUPPLY.

Sufficient fresh air supply is essential to ensure optimum combustion and the 

area of air supply openings must be in compliance with applicable codes and 

regulations. Air openings must be kept wide open when the burner is firing 

and clear from restriction to flow.

d. CHECK VENT.

Proper venting is essential to assure efficient combustion. Insufficient draft or 

overdraft promotes hazards and inefficient burning. Check to be sure that vent 

is in good condition, sized properly and with no obstructions.

e. COMBUSTION ANALYSIS.

Perform an "as is" combustion analysis (CO, O2, etc.) with a warmed up unit 

at high and low fire, if possible. In addition to data obtained from combustion 

analysis, also record the following:

i. Inlet fuel pressure at burner (at high & low fire)

ii. Draft at inlet to draft hood or barometric damper

1) Draft hood: high, medium, and low

2) Barometric Damper: high, medium, and low

iii. Steam pressure, water temperature, or process fluid pressure or 

temperature entering and leaving the boiler, steam generator, or 

process heater.

Deleted: above 
Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-15

iv. Unit rate if meter is available.

With above conditions recorded, make the following checks and corrective actions as 

necessary: 

2. CHECKS & CORRECTIONS

a. CHECK BURNER CONDITION.

Dirty burners or burner orifices will cause boiler, steam generator, or process 

heater output rate and thermal efficiency to decrease. Clean burners and 

burner orifices thoroughly. Also, ensure that fuel filters and moisture traps are 

in place, clean, and operating properly, to prevent plugging of gas orifices. 

Confirm proper location and orientation of burner diffuser spuds, gas canes, 

etc. Look for any burned-off or missing burner parts, and replace as needed.

b. CHECK FOR CLEAN BOILER, STEAM GENERATOR, OR PROCESS 

HEATER TUBES & HEAT TRANSFER SURFACES.

External and internal build-up of sediment and scale on the heating surfaces 

creates an insulating effect that quickly reduces unit efficiency. Excessive fuel 

cost will result if the unit is not kept clean. Clean tube surfaces, remove scale 

and soot, assure proper process fluid flow and flue gas flow.

c. CHECK WATER TREATMENT & BLOWDOWN PROGRAM.

Soft water and the proper water or process fluid treatment must be uniformly 

used to minimize scale and corrosion. Timely flushing and periodic 

blowdown must be employed to eliminate sediment and scale build-up on a 

boiler, steam generator or process heater.

d. CHECK FOR STEAM, HOT WATER OR PROCESS FLUID LEAKS

Repair all leaks immediately since even small high-pressure leaks quickly lead 

to considerable fuel, water and steam losses. Be sure there are no leaks 

through the blow-off, drains, safety valve, by-pass lines or at the feed pump, if 

used.

3. SAFETY CHECKS

a. Test primary and secondary low water level controls.

b. Check operating and limit pressure and temperature controls.

c. Check pilot safety shut off operation.

d. Check safety valve pressure and capacity to meet boiler, steam generator or 

process heater requirements.
Proposed Amended Rule 1146.1 (Cont.) (Amended May 13, 1994)

1146.1-16

e. Check limit safety control and spill switch.

4. ADJUSTMENTS

While taking combustion readings with a warmed up boiler, steam generator, or 

process heater at high fire perform checks and adjustments as follows:

a. Adjust unit to fire at rate; record fuel manifold pressure.

b. Adjust draft and/or fuel pressure to obtain acceptable, clean combustion at 

both high, medium and low fire. Carbon Monoxide (CO) value should always 

be below 400 parts per million (PPM) at 3% 02. If CO is high make necessary 

adjustments.

Check to ensure boiler, steam generator, or process heater light offs are 

smooth and safe. A reduced fuel pressure test at both high and low fire should 

be conducted in accordance with the manufacturers instructions and 

maintenance manuals.

c. Check and adjust operation of modulation controller. Ensure proper, efficient 

and clean combustion through range of firing rates.

When above adjustments and corrections have been made, record all data.

5. FINAL TEST

Perform a final combustion analysis with a warmed up boiler, steam generator, or 

process heater at high, medium and low fire, whenever possible. In addition to data 

from combustion analysis, also check and record:

a. Fuel pressure at burner (High, Medium, and Low).

b. Draft above draft hood or barometric damper (High, Medium and Low).

c. Steam pressure or water temperature entering and leaving boiler, steam 

generator, or process heater.

d. Unit rate if meter is available.

When the above checks and adjustments have been made, record data and attach 

combustion analysis data to boiler, steam generator, or process heater records 

indicating name and signature of person, title, company name, company address and 

date the tuneup was performed.