SACAQMD RULE 411 BOILER NOx                           
LAST REVISED 02/02/95



                           RULE 411, BOILER NOX
                            (Adopted 02-02-95)
                                     
                                   INDEX



100 GENERAL
    101  PURPOSE
    102  APPLICABILITY
    110  EXEMPTION - EQUIPMENT RATING
    111  EXEMPTION - ELECTRIC UTILITY BOILERS
    112  EXEMPTION - PROCESS HEATERS, KILNS, AND FURNACES
    113  EXEMPTION - WASTE HEAT RECOVERY BOILERS
    114  EXEMPTION - REMOVAL FROM SERVICE
    115  EXEMPTION - LOW FUEL USAGE

200 DEFINITIONS
    201  ANNUAL HEAT INPUT
    202  BEST AVAILABLE RETROFIT CONTROL TECHNOLOGY (BARCT)
    203  BIOMASS
    204  BIOMASS BOILER OR STEAM GENERATOR
    205  BOILER OR STEAM GENERATOR
    206  BRITISH THERMAL UNIT (BTU)
    207  HEAT INPUT
    208  GASEOUS FUEL
    209  HIGH HEATING VALUE (HHV)
    210  MALFUNCTION
    211  NITROGEN OXIDES (NOx)
    212  NON-GASEOUS FUEL
    213  PARTS PER MILLION BY VOLUME (PPMV)
    214  PROCESS HEATER
    215  RATED HEAT CAPACITY
    216  REASONABLY AVAILABLE CONTROL TECHNOLOGY (RACT)
    217  RETROFIT
    218  SHUTDOWN
    219  STANDARD CONDITIONS
    220  STARTUP
    221  THERM
    222  UNIT
    223  WOOD

300 STANDARDS
    301  RACT EMISSIONS LIMITS - GASEOUS FUEL FIRING
    302  RACT EMISSIONS LIMITS - NONGASEOUS FUEL FIRING
    303  RACT EMISSIONS LIMITS - BIOMASS FUEL FIRING
    304  BARCT EMISSIONS LIMITS - GASEOUS FUEL FIRING
    305  BARCT EMISSIONS LIMITS - NONGASEOUS FUEL FIRING
    306  BARCT EMISSIONS LIMITS - BIOMASS FUEL FIRING
    307  EMISSION LIMIT - EMERGENCY STANDBY NONGASEOUS FUEL FIRING
    308  LOW FUEL USAGE\REMOVAL FROM SERVICE
    309  EQUIPMENT REQUIREMENT - FUEL CONSUMPTION


400 ADMINISTRATIVE REQUIREMENTS
    401  COMPLIANCE SCHEDULE
    
500 MONITORING AND RECORDS
    501  TEST METHODS
    502  RECORDKEEPING  
    
    
100 GENERAL

    101  PURPOSE:  To limit NOX and CO emissions from existing
         industrial, institutional, and commercial boilers, steam
         generators, and process heaters.

    102  APPLICABILITY:  The requirements of this Rule shall apply
         to boilers, steam generators and process heaters with
         rated heat inputs of 5 million Btu per hour or greater,
         used in industrial, institutional, and commercial
         operations.

    110  EXEMPTION - EQUIPMENT RATING:  The requirements of this
         Rule shall not apply to any  unit with a rated heat input
         capacity of less than 5 million Btu per hour.

    111  EXEMPTION - ELECTRIC UTILITY BOILERS: The requirements of 
         this Rule shall not apply to any unit that is exclusively
         used by an electric utility to generate electricity.

    112  EXEMPTION - PROCESS HEATERS, KILNS, AND FURNACES:  The
         requirements of this Rule shall not apply to process
         heaters, kilns, and furnaces where the products of
         combustion come into direct contact with the material to
         be heated.

    113  EXEMPTION - WASTE HEAT RECOVERY BOILERS: The requirements
         of this Rule shall not apply to waste heat recovery
         boilers used to recover heat from the exhaust of
         combustion turbines or reciprocating internal combustion
         engines.

    114  EXEMPTION - REMOVAL FROM SERVICE:  The requirements of
         Sections 301 through 307 this rule shall not apply to any
         unit that is expected to be taken out of service on or
         before May 31, 1997 provided that the owner or operator
         complies with one of the requirements listed in Sections
         308 and 401.5.

    115  EXEMPTION - LOW FUEL USAGE:  The requirements of Sections
         301 through 307 shall not apply to any unit that uses
         less than 90,000 therms per year of fuel provided that
         the owner or operator complies with one of the
         requirements listed in Sections 308 and 401.4.

200 DEFINITIONS

    201  ANNUAL HEAT INPUT:  The total input of fuels burned by a
         unit in a calendar year, as determined from the higher
         heating value and cumulative annual usage of each fuel.

    202  BEST AVAILABLE RETROFIT CONTROL TECHNOLOGY (BARCT):  Best
         available retrofit control technology as defined in
         Section 40406 of the California Health and Safety Code is
         "an emission limitation that is based on the maximum
         degree of reduction achievable, taking into account
         environmental, energy, and economic impacts by each class
         or category of sources."  These limits are specified in
         Sections 304, 305, and 306.

    203  BIOMASS:  Any solid, organic material used as a fuel
         source for boilers or steam generators including, but not
         limited to, wood, almond shells, or agricultural waste.

    204  BIOMASS BOILER OR STEAM GENERATOR:  Any unit used in any
         institutional, commercial, or industrial operation that
         is designed to burn biomass fuel to produce steam, heat
         water and/or other fluids, and/or generate electricity. 
         For the purpose of this rule, a unit that simultaneously
         burns multiple fuels including biomass fuel shall be
         considered a biomass boiler or steam generator.

    205  BOILER OR STEAM GENERATOR:  Any unit fired with any fuel
         used to produce steam or heat water 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 reciprocating internal
         combustion engines.

    206  BRITISH THERMAL UNIT (BTU):  The amount of heat required
         to raise the temperature of one pound of water from 59 oF
         to 60  oF at one atmosphere.

    207  HEAT INPUT:  The chemical heat released due to fuel
         combustion in a combustion unit, using the higher heating
         value of the fuel.  This does not include the sensible
         heat of incoming combustion air.

    208  GASEOUS FUEL:  Any fuel which is a gas at standard
         conditions.

    209  HIGH HEATING VALUE (HHV):  The total heat liberated per
         mass of fuel burned (Btu per pound), when fuel and dry
         air at standard conditions undergo complete combustion
         and all resultant products are brought to their standard
         states at standard conditions.  If certification of the
         HHV is not provided by the third party fuel supplier, it
         shall be determined by one of the test methods specified
         in Section 501.2.

    210  MALFUNCTION:  Any sudden and unavoidable failure of air
         pollution control equipment or process equipment or of a
         process to operate in a normal or usual manner.  Failures
         that are caused entirely or in part by poor maintenance,
         careless operation, or any other preventable upset
         condition or preventable equipment breakdown shall not be
         considered malfunction.

    211  NITROGEN OXIDES (NOX):  The sum of nitric oxide and
         nitrogen dioxide in the flue gas.

    212  NONGASEOUS FUEL:  Any fuel which is not a gas at standard
         conditions.

    213  PARTS PER MILLION BY VOLUME (PPMV):  The ratio of the
         number of gas molecules of a given species, or group, to
         the number of millions of total gas molecules.

    214  PROCESS HEATER:  Any unit fired with any fuel which
         transfers heat from combustion gases to water or process
         streams.  Process heater does not include any dryer in
         which the material being dried is in direct contact with
         the products of combustion, cement or lime kilns, glass
         melting furnaces, or smelters.

    215  RATED HEAT CAPACITY:  The heat input capacity in million
         Btu per hour specified in 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 name plate,
         the maximum heat input shall be considered as rated heat
         input.

    216  REASONABLY AVAILABLE CONTROL TECHNOLOGY (RACT):  The
         lowest emission limitation that a particular unit is
         capable of meeting by using measures that are reasonably
         available in terms of technological and economic
         feasibility.  These limits are specified in Sections 301,
         302, and 303.
    
    217  RETROFIT:  Any physical change to an emissions unit
         necessary for reducing NOx and CO emissions to comply with
         the NOx and CO emissions limits specified in Sections 301
         through 307 of this rule, including, but not limited to,
         burner replacement, addition of emissions control
         equipment, and addition of oxygen trim systems.  Changes
         in the method of operation shall not be considered as
         retrofit.

    218  SHUTDOWN:  The period of time a unit is cooled from its
         normal operating temperature to ambient temperature.  The
         shutdown period shall be limited to two hours.

    219  STANDARD CONDITIONS:  For the purpose of this rule,
         standard conditions are 68 oF and one atmosphere.

    220  STARTUP:  The period of time a unit is heated from
         ambient temperature to its operating temperature as
         specified by the unit manufacturer.

    221  THERM:  One hundred thousand (100,000) Btu's.

    222  UNIT:  Any boiler, steam generator, as defined in Section
         205, or process heater, as defined in Section 214.

    223  WOOD:  Wood, wood residue, bark, or any derivative fuel
         or residue thereof, in any form, including but not
         limited to sawdust, dust from sanding, wood chips,
         scraps, slabs, millings, shavings, and processed pellets
         made from wood or other forest residues.

300 STANDARDS

    301  RACT EMISSIONS LIMITS - GASEOUS FUEL FIRING
         301.1   NOx Emissions:  The NOX emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 70
                 parts per million by volume on a dry basis,
                 averaged over a period of 15 consecutive minutes,
                 corrected to three percent oxygen (70 ppmvd @ 3%
                 O2), when firing on gaseous fuels. 
         301.2   CO Emissions: The CO emissions from any unit with
                 an annual heat input greater than or equal to
                 90,000 therms per year shall not exceed 400 parts
                 per million by volume on a dry basis, averaged
                 over a period of 15 consecutive minutes,
                 corrected to 3 percent oxygen (400 ppmvd @ 3%
                 O2), when firing on gaseous fuels.

    302  RACT EMISSIONS LIMITS - NONGASEOUS FUEL FIRING
         302.1   NOx Emissions:  The NOX emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 115
                 parts per million by volume on a dry basis,
                 averaged over a period of 15 consecutive minutes,
                 corrected to three percent oxygen (115 ppmvd @ 3%
                 O2) when firing on nongaseous fuels.
         302.2   CO Emissions:  The CO emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 400
                 parts per million by volume on a dry basis,
                 averaged over a period of 15 consecutive minutes,
                 corrected to three percent oxygen (400 ppmvd @ 3%
                 O2), when firing on nongaseous fuels.

    303  RACT EMISSIONS LIMITS - BIOMASS FUEL FIRING
         303.1   NOx Emissions:  The NOX emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 110
                 parts per million by volume on a dry basis, on a
                 rolling three hour average, corrected to twelve
                 percent carbon dioxide (110 ppmvd @ 12% CO2), 
                 when firing on biomass fuels.
         303.2   CO Emissions:  The CO emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 400
                 parts per million by volume on a dry basis, on a
                 rolling three hour average, corrected to twelve
                 percent carbon dioxide (400 ppmvd @ 12% CO2),
                 when firing on biomass fuels.

    304  BARCT EMISSIONS LIMITS - GASEOUS FUEL FIRING
         304.1   NOx Emissions:  The NOX emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 30
                 parts per million by volume on a dry basis,
                 averaged over a period of 15 consecutive minutes,
                 corrected to three percent oxygen (30 ppmvd @ 3%
                 O2), when firing on gaseous fuels. 
         304.2   CO Emissions: The CO emissions from any unit with
                 an annual heat input greater than or equal to
                 90,000 therms per year shall not exceed 400 parts
                 per million by volume on a dry basis, averaged
                 over a period of 15 consecutive minutes,
                 corrected to 3 percent oxygen (400 ppmvd @ 3%
                 O2), when firing on gaseous fuels.

    305  BARCT EMISSIONS LIMITS - NONGASEOUS FUEL FIRING
         305.1   NOx Emissions:  The NOX emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 40
                 parts per million by volume on a dry basis,
                 averaged over a period of 15 consecutive minutes,
                 corrected to three percent oxygen (40 ppmvd @ 3%
                 O2), when firing on nongaseous fuels.
         305.2   CO Emissions:  The CO emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 400
                 parts per million by volume on a dry basis,
                 averaged over a period of 15 consecutive minutes,
                 corrected to three percent oxygen (400 ppmvd @ 3%
                 O2), when firing on nongaseous fuels.

    306  BARCT EMISSIONS LIMITS - BIOMASS FUEL FIRING
         306.1   NOx Emissions:  The NOX emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 70
                 parts per million by volume on a dry basis, on a
                 rolling three hour average, corrected to twelve
                 percent carbon dioxide (70 ppmvd @ 12% CO2), when
                 firing on biomass fuels.
         306.2   CO Emissions:  The CO emissions from any unit
                 with an annual heat input greater than or equal
                 to 90,000 therms per year shall not exceed 400
                 parts per million by volume on a dry basis, on a
                 rolling three hour average, corrected to twelve
                 percent carbon dioxide (400 ppmvd @ 12% CO2),
                 when firing on biomass fuels.
    
    307  EMISSION LIMIT - EMERGENCY STANDBY NONGASEOUS FUEL FIRING
         307.1   NOx Emissions:  The NOx emissions from any unit
                 which normally burns gaseous fuel but burns
                 nongaseous fuel only during emergency
                 interruption of gaseous fuel supply by the
                 serving utility shall not exceed 150 parts per
                 million by volume on a dry basis, averaged over
                 a period of 15 consecutive minutes, corrected to
                 three percent oxygen (150 ppmvd @ 3% O2), when
                 firing on nongaseous fuel.  Operation of the unit
                 under this Section shall not exceed 168 hours per
                 calendar year, excluding equipment and emission
                 testing time, not exceeding 48 hours per calendar
                 year.
    
    308  LOW FUEL USAGE\REMOVAL FROM SERVICE:  Any unit with an
         annual heat input of less than 90,000 therms per year, or
         any unit that will be operated with annual heat input of
         less than 90,000 therms, or any unit which will be
         removed from service by May 31, 1997 shall meet one of
         the following conditions:
         308.1   The unit shall be operated in a manner that
                 maintains stack-gas oxygen concentrations at less
                 than or equal to 3.00 % by volume on a dry basis;
                 or
         308.2   The unit shall be tuned at least once per year by
                 a qualified technician.  The tune-up shall be
                 performed in accordance with the procedure
                 described in ATTACHMENT A; or
         308.3   The unit shall be operated in compliance with the
                 applicable emission levels specified in Sections
                 301 through 307.

    309  EQUIPMENT REQUIREMENT - FUEL CONSUMPTION
         309.1   No later than February 2, 1996 the owners or
                 operators of units subject to the requirements of
                 Sections 307 shall install a non-resetting
                 totalizing hour meter on each unit.
         309.2   No later than February 2, 1996 the owners or
                 operators of units subject to the requirements of
                 Section 308 shall:
             a.  Install a non-resetting totalizing fuel meter in
                 the fuel line for each fuel burned.  If a
                 volumetric flow meter is installed, it must be
                 equipped with a pressure and temperature gauges;
                 or
             b.  Install a non-resetting totalizing hour meter. 
                 In this case, the fuel usage shall be calculated
                 by multiplying the number of operating hours for
                 the unit by the maximum fuel usage for the unit
                 as specified by the unit manufacturer.
         
400 ADMINISTRATIVE REQUIREMENTS

    401  COMPLIANCE SCHEDULE
         401.1   RACT EMISSION LIMITS:  The owner or operator of
                 any unit in existence prior to February 2, 1995
                 subject to the emission limits of Sections 301
                 through 303 shall comply with these limits
                 effective May 31, 1995 unless retrofitting is
                 required.  If retrofitting is required to achieve
                 these limits, the owner or operator shall comply
                 with the increments of progress of Section 401.3
                 and be in compliance with the BARCT limits by the
                 date specified in Section 401.3.  Interim
                 compliance with the limits of Sections 301
                 through 303 does not exclude the owner or
                 operator from final compliance with the limits of
                 Sections 304 through 306 and the increments of
                 progress of Section 401.3.
         401.2   BARCT EMISSION LIMITS:  The owner or operator of
                 any unit subject to the emission limits of
                 Sections 304 through 306 shall comply with these
                 limits effective May 31, 1997 and shall do so in
                 accordance with the increments of progress of
                 Section 401.3.
         401.3   INCREMENTS OF PROGRESS:  The owner or operator of
                 any unit subject to the  emissions limits of
                 Sections 301 through 307 shall comply with the
                 following increments of progress:
             a.  By May 31, 1995, submit a compliance plan
                 containing the following:
                 1. A list which, for each unit, indicates the
                    current emission level in ppmvd and the
                    retrofitting required to meet the limits of
                    Sections 304 through 307.
                 2. A description of the method used to determine
                    the current emission level of each unit.
                 3. A schedule demonstrating compliance with the
                    emission limits of Sections 304 through 307
                    and the remaining increments of this Section.
             b.  By November 30, 1995, submit a complete
                 application for an authority to construct for the
                 modifications necessary to meet the limits of
                 Sections 304 through 307.
             c.  By November 30, 1996, begin construction.
             d.  By March 31, 1997, complete construction.
             e.  By May 31, 1997, comply with the emission limits
                 of Sections 304 through 307.  This shall include
                 the submittal of a complete source test report
                 indicating compliance.
         401.4   LOW FUEL USAGE: The owner or operator of any unit
                 in existence prior to February 2, 1995 subject to
                 the requirements of Section 308 because of low
                 fuel usage shall meet the following increments of
                 progress:
             a.  By May 31, 1995, submit to the Air Pollution
                 Control Officer a petition (a petition form can
                 be obtained from the District) requesting an
                 exemption from the requirements of Sections 301
                 through 307.
             b.  By November 30, 1995, submit to the Air Pollution
                 Control Officer a compliance plan containing  the
                 following information:
                 1. A selection of one of the compliance options
                    specified in Section 308 for achieving
                    compliance for the unit.
                 2. An Authority to Construct application for
                    modification of the Permit to Operate to
                    include a condition limiting the annual fuel
                    usage for the unit to less than 90,000
                    therms.
             c.  By March 31, 1996, comply with the selected
                 compliance option.

             If the fuel usage for any unit subject to the
             requirements of Section 308 exceeds 90,000 therms
             for any calendar year, then the unit must be
             operated in compliance with the applicable NOx and CO
             emissions limits in Sections 301 through 307.

         401.5   REMOVAL FROM SERVICE: The owner or operator of
                 any unit in existence prior to February 2, 1995
                 that is expected to be removed from service by
                 May 31, 1997 shall comply with the following:
             a.  By May 31, 1995, submit to the Air Pollution
                 Control Officer a petition (a petition form can
                 be obtained from the District) requesting an
                 exemption from the requirements of Section 301
                 through 307.
             b.  By November 30, 1995, submit to the Air Pollution
                 Control Officer a compliance plan containing  the
                 following information:
                 1. A selection of one of the compliance options
                    specified in Section 308 for achieving
                    compliance for the unit.
                 2. An Authority to Construct application for
                    modification of the Permit to Operate.
             b.  By March 31, 1996, comply with the selected
                 compliance option.
             c.  By May 31, 1997, discontinue operation of the
                 unit, disconnect fuel supply line(s), and notify
                 the Air Pollution Control Officer, in writing, of
                 the removal from service.

             Operation of any unit beyond May 31, 1997 shall be
             done compliance with the applicable NOx and CO
             emissions limits in Sections 301 through 307.

         401.6   REPORTING - TUNE-UP VERIFICATION: The owner or
                 operators of units subject to the requirements of
                 Section 308.2 shall submit to the Air Pollution
                 Control Officer a tune-up verification report not
                 less than once every 12 months for each unit. The
                 first test or tune-up report shall be submitted
                 to the Air Pollution Control Officer no later
                 than November 30, 1995.
         401.7   SOURCE TESTING FREQUENCY:  The owner or operator
                 of units subject to the requirements of Sections
                 301 through 308 shall conduct source testing
                 according to the following schedule:
             a.  Any unit that is rated at 25 million Btu per hour
                 input or greater shall be tested annually.
             b.  Any unit that is rated at greater than 5 million
                 Btu per hour input but less than less than 25
                 million Btu per hour input shall be tested
                 biennially.

500 MONITORING AND RECORDS

    501  TEST METHODS
         501.1   GASEOUS EMISSIONS: Compliance with the NOX
                 emission requirements and the stack gas carbon
                 monoxide and oxygen requirements of Sections 301
                 through 308 shall be determined using the test
                 methods specified below.  All emissions
                 determinations shall be made in the as-found
                 operating condition, except no compliance
                 determination shall be established during unit
                 startup or shutdown, or during malfunction as
                 defined in Section 210.  Test reports shall
                 include the operational characteristics of all
                 flue-gas NOX reduction equipment.
             a.  Oxide of Nitrogen - ARB Method 100 or EPA Method
                 7E.
             b.  Carbon Monoxide - ARB Method 100 or EPA Method
                 10.
             c.  Stack Gas Oxygen - ARB Method 100 or EPA Method
                 3A.
             d.  Carbon Dioxide - ARB Method 100 or EPA Method 3A.
                 
         501.2   HIGH HEAT VALUE:  HHV shall be determined
                 by one of the following test methods:
             a.  ASTM D 2015-85 for solid fuels; or
             b.  ASTM D 240-87 or ASTM D 2382-88 for liquid
                 hydrocarbon fuels; or
             c.  ASTM D 1826-88, or ASTM D 1945-81 in
                 conjunction with ASTM D 3588-89 for gaseous
                 fuels.

    502  RECORDKEEPING
         502.1   The owner or operator of units subject to the
                 requirements of Section 307 shall monitor and
                 record for each unit the cumulative annual hours
                 of operation on each non-gaseous fuel.  The data
                 shall be kept for the most recent 2 years period
                 and shall be made available to the Air Pollution
                 Control Officer upon request.
         502.2   The owner or operator of units subject to the
                 requirements of Section 308 shall monitor and
                 record for each unit the HHV and cumulative
                 gaseous and non-gaseous fuel usage.  The data
                 shall be kept for the most recent 2 year period
                 and shall be made available to the Air Pollution
                 Control Officer upon request.

Tuning Procedure

Nothing in this 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 number (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 values and if the CO
    emissions are low and there is no smoke, the unit is probably
    operating at near optimum efficiency - at this particular firing
    rate. However, complete the remaining portion of this procedure
    to determine whether still lower oxygen levels are practical.

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.

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 wind
         box/furnace pressure differential, built in air-flow
         limits, etc.

6.  Develop an O2 /CO curve (for gaseous fuels) or 02/smoke curve
    (for liquid fuels) similar to those shown in Figures 1 and 2
    using the excess oxygen and CO or smoke-spot number data
    obtained at each combustion air flow setting.

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 levels.

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 mix, thereby allowing operations with
less air.

8.  Add 0.5 to 2.0 percent 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
    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, setting should optimize conditions at
    the 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.