SACRAMENTO METROPOLITAN AQMD RULES AND REGULATIONS 

August 1, 1996XX-XX-2010 414-1 

RULE 414, NATURAL GAS-FIRED WATER HEATERS, BOILERS AND PROCESS HEATERS RATED 

LESS THAN 1,000,000 BTU PER HOUR

Adopted 08-01-96 

(Amended XX-XX-10)

INDEX

100 GENERAL

101 PURPOSE 

102 APPLICABILITY 

110 EXEMPTION, LARGE WATER HEATERS

1110 EXEMPTION, WATER HEATERS IN RECREATIONAL VEHICLES 

1121 EXEMPTION, POOL/SPA HEATERSWATER HEATERS IN SWIMMING POOLS AND 

HOT TUBS

1132 EXEMPTION, WATER HEATERS, BOILERS AND PROCESS HEATERS USING A FUEL 

OTHER THAN NATURAL GAS FIRED WITH LIQUEFIED PETROLEUM GAS

200 DEFINITIONS

201 BOILER

2012 BRITISH THERMAL UNITBTU

2023 HEAT INPUT 

2034 HEAT OUTPUT

205 LIQUEFIED PETROLEUM GAS

2046 MOBILE HOME WATER HEATER 

2057 NATURAL GAS 

206 NATURAL GAS-FIRED WATER HEATER

208 POOL/SPA HEATER

209 PROCESS HEATER

20710 RATED HEAT INPUT CAPACITY 

20811 RECREATIONAL VEHICLE

212 WASTE HEAT RECOVERY BOILER

213 WATER HEATER

300 STANDARDS

301 NITROGEN OXIDES EMISSION LIMITS

302 SELL-THROUGH OF WATER HEATERS, BOILERS AND PROCESS HEATERS

400 ADMINISTRATIVE REQUIREMENTS 

401 COMPLIANCE SCHEDULE

4021 CERTIFICATION REPORTREQUIREMENT

4032 MANUFACTURERS' LABELING REQUIREMENT 

404 CALCULATION FOR DETERMINATION OF HEAT OUTPUT

405 CALCULATION FOR DETERMINATION OF STORAGE TANK CAPACITY

500 MONITORING AND RECORD KEEPING

501 TESTING PROCEDURE 

502 DURATION OF RECORDS
SACRAMENTO METROPOLITAN AQMD RULES AND REGULATIONS 

414-2 August 1, 1996XX-XX-2010

100 GENERAL

101 PURPOSE: To limit the emission of nitrogen oxides (NOx) from natural gas-fired water 

heaters, boilers and process heaters. 

102 APPLICABILITY: This rule shall apply to any person who manufactures, distributes, offers 

for sale, sells, or installs any type of natural gas-fired water heater (such as tank or 

tankless/instantaneous), boiler or process heater, with a rated heat input capacity less than 

75,0001,000,000 British thermal units per hour (Btu/hr), fired with gaseous or nongaseous 

fuels, for use in this District. 

110 EXEMPTION, LARGE WATER HEATERS: This rule shall not apply to water heaters with a 

rated heat input of 75,000 Btu/hr or greater.

1110 EXEMPTION, WATER HEATERS IN RECREATIONAL VEHICLES: This rule shall not 

apply to water heaters used in recreational vehicles. 

1121 EXEMPTION, POOL/SPA HEATERSWATER HEATERS IN SWIMMING POOLS AND HOT 

TUBS: This rule shall not apply to water pool/spa heaters with a heat input rating of less than 

75,000 Btu/hr used exclusively to heat swimming pools and hot tubs. 

1132 EXEMPTION, WATER HEATERS, BOILERS AND PROCESS HEATERS USING A FUEL 

OTHER THAN NATURAL GAS FIRED WITH LIQUEFIED PETROLEUM GAS: This rule 

shall not apply to water heaters, boilers and process heaters using any fuel other than natural 

gas fired with liquefied petroleum gas. 

200 DEFINITIONS 

201 BOILER: Any external combustion equipment fired with any fuel used to produce hot water 

or steam, excluding waste heat recovery boilers.

2012 BRITISH THERMAL UNIT (Btu)BTU: The amount of heat required to raise the temperature 

of one pound of water from 59F to 60F at one atmosphereBritish thermal unit or units. 

2023 HEAT INPUT: The actual amount of heat released by natural gas burned in a water 

heaterThe heat of combustion released by fuels burned in a unit based on the higher heating 

value of the fuel. This does not include the enthalpy of incoming combustion air. 

2034 HEAT OUTPUT: The product Ho as defined in Section 4049.3 of the South Coast AQMD 

Protocol, as referenced in Section 501 of this rule.

205 LIQUEFIED PETROLEUM GAS: A compressed gas composed of one or more of the 

following flammable hydrocarbons: propane, n-butane, isobutane, propylene, and butenes.

2046 MOBILE HOME WATER HEATER: A natural gas-fired water heater manufactured 

exclusively for mobile home use. 

2057 NATURAL GAS: A mixture of gaseous hydrocarbons containing at least 80 percent methane 

by volume as determined according to American Standard Test Method (ASTM) D1945-64. 

206 NATURAL GAS-FIRED WATER HEATER: A closed vessel in which water is heated by the 

combustion of natural gas and is withdrawn for use external to the vessel at pressures not 

exceeding 160 psig, including the apparatus by which heat is generated and all controls and 

devices necessary to prevent water temperatures from exceeding 210F (99C).

208 POOL/SPA HEATER: A device in which water is heated when pool or spa water circulates 

through a heat exchanger.
SACRAMENTO METROPOLITAN AQMD RULES AND REGULATIONS 

August 1, 1996XX-XX-2010 414-3 

209 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.

20710 RATED HEAT INPUT CAPACITY: 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. 

20811 RECREATIONAL VEHICLE: A motor home, travel trailer, truck camper, or camping trailer, 

with or without motive power, designed for human habitation for recreational, emergency, or 

other occupancy, which meets all of the following criteria: 1) contains less than 320 square 

feet of internal living room area, excluding built-in equipment, including, but not limited to 

wardrobe, closets, cabinets, kitchen units or fixtures, and bath or toilet rooms; 2) it contains 

400 square feet or less of gross area measured at maximum horizontal projections; 3) it is

built on a single chassis; and 4)it is either self propelled, truck mounted, or permanently 

towable on the highways without a permit as defined pursuant to Section 18010 of the 

California Health and Safety Code. 

212 WASTE HEAT RECOVERY BOILER: A device that recovers normally unused energy and 

converts it to usable heat. Devices incorporating duct or supplemental burners that are 

designed to supply 50% or more of the total rated heat input capacity of the device are not 

considered waste heat recovery boilers, but are considered boilers. Waste heat recovery 

boilers are also referred to as heat recovery steam generators. 

213 WATER HEATER: A closed vessel in which water is heated and is withdrawn for use 

external to the vessel at pressures not exceeding 160 psig, including the apparatus by which 

heat is generated and all controls and devices necessary to prevent water temperatures from 

exceeding 210 °F (99 °C).

300 STANDARDS

301 NITROGEN OXIDES EMISSION LIMITS: A person shall only distribute, offer for sale, sell, or 

install within the Sacramento Metropolitan Air Quality Management District either of the 

following a water heater, boiler or process heater with certified NOx and CO emissions less 

than or equal to the following limits: 

301.1 A natural gas-fired water heater that emits less than or equal to 40 nanograms of 

nitrogen oxides (calculated as NO2) per joule (93 pounds per billion Btu) of heat 

output; and is certified in accordance with Section 402.

301.2 A mobile home natural gas-fired water heater that emits less than or equal to 50 

nanograms of nitrogen oxides (calculated as NO2) per joule (116 pounds per billion 

Btu) of heat output; and is certified in accordance with Section 402.

NOx Limit

Nanograms per Joule of Heat Output

(ppmv @ 3% O2)*

CO Limit

ppmv @ 3% O2

Heat Input 

Range

and

Type Effective

3/1/1997

Effective

1/1/2011

Effective

1/1/2013

Effective

1/1/2011

< 75,000 Btu/hr

Mobile Home

All others

50 

40 

40 (55)

10 (15)

No Limit

No Limit

75,000 to < 400,000 Btu/hr

Pool/Spa

All others

No Limit

No Limit

40 (55)

40 (55) 14 (20)

No Limit

No Limit

400,000 to < 1million Btu/hr

All Types No Limit 14 (20)

 

400

 * Where limits are shown in units of both nanograms per joule of heat output and ppmv at 

3% oxygen, compliance can be demonstrated using either limit.
SACRAMENTO METROPOLITAN AQMD RULES AND REGULATIONS 

414-4 August 1, 1996XX-XX-2010

302 SELL-THROUGH OF WATER HEATERS, BOILERS AND PROCESS HEATERS: An 

applicable water heater, boiler or process heater manufactured prior to the January 1, 2011 

or the January 1, 2013 effective date specified for that unit in Section 301 may be distributed, 

offered for sale, or sold for up to 6 months after the specified effective date. In addition, a 

water heater, boiler or process heater manufactured before the effective date specified for 

that unit in Section 301 may be installed at any time, after the specified effective date, so long 

as it complied with the standards in Section 301 and 302 in effect at the time the unit was

sold to the owner/operator of the water heater, boiler or process heater.

400 ADMINISTRATIVE REQUIREMENTS

401 COMPLIANCE SCHEDULE: Effective March 1, 1997, no person shall distribute, offer for 

sale, sell, or install any natural gas-fired water heater which does not comply with the 

requirements of Section 300.

4021 CERTIFICATION REQUIREMENT REPORT:

4021.1 A manufacturer of any natural gas fired water heater, boiler, or process heater

subject to Section 300 shall submit to the Air Pollution Control Officer (APCO) a

statement certifying compliance report that water heaters demonstrates each model

manufactured by it and subject to this rule are is in compliance with the provisions of 

Section 300 at least 30 days prior to sale being sold or distributed for sale within the 

District. Regardless of whether a permit is required, the manufacturer submitting a 

certification report must pay the fee in Rule 301, PERMIT FEES – STATIONARY 

SOURCE, Section 311. The compliance report shall include the following 

information:

a. Name and address of manufacturer;

b. Brand name and model;

c. Model number as it appears on the rating plate;

d. Fuel type unit is fired with;

e. Description of each water heater model being certified;

f. Heat input rating;

g. All compliance test procedures and results, as performed by an independent 

testing laboratory, in accordance with Section 501;

h. All calculations for determining compliance; and

i. A signed and dated statement attesting to the accuracy of all statements 

and information in the compliance report.

401.2 In lieu of Sections 401.1(f) and 401.1(g), a manufacturer may submit to the District, 

at least 30 days prior to a model being sold or distributed for sale within the District, 

an approved South Coast Air Quality Management District (SCAQMD) certification 

pursuant to SCAQMD Rules 1121 or 1146.2.

The statement shall be signed, dated, and shall attest to the accuracy of all 

information. The statement shall include the brand name, model number, the input 

rating as it appears on the water heater rating plate, and test results in accordance 

with Section 501; or

402.2 A manufacturer shall submit to this District an approved South Coast Air Quality 

Management District certification. Any model of natural gas-fired water heater 

certified as complying with the South Coast Air Quality Management District’s Rule 

1121 prior to July 1, 1995, need not be recertified to the test protocol specified in 

Section 501 until such time as required by the South Coast Air Quality Management 

District.

4032 MANUFACTURERS' LABELING REQUIREMENT: A manufacturer shall display the model 

number and the manufactured year of the water heater, boiler or process heater complying 

with Section 300 on the shipping carton and on the rating plate of each water heater unit. 

The manufacturer shall also display the certification status on the shipping carton and on the 

water heater, boiler or process heater. 
SACRAMENTO METROPOLITAN AQMD RULES AND REGULATIONS 

August 1, 1996XX-XX-2010 414-5 

404 CALCULATION FOR DETERMINATION OF HEAT OUTPUT: Heat output is computed 

using the following equation, as contained in the Protocol:

Ho = MCpi(Tdel - Tin) + VstDnCp2(Tmax – To)

Where: Ho = heat output in British thermal units.

M = mass of the water withdrawn in pounds.

Cpi = specific heat of water at the average temperature 

(Tdel + Tin)/2, British thermal units/pound o

F.

Tdel = average delivery temperature oF.

Tin = average inlet temperature o

F.

Vst = storage tank capacity in gallons, as determined in Section 

405.

Dn = density of water at the average temperature (Tmax + To)/2 in 

pounds/gallon.

Cp2 = specific heat of water at the average temperature 

(Tmax + To)/2 in British thermal units/pound o

F.

Tmax = maximum mean tank temperature recorded after cutout 

following the test draw oF.

To = the maximum mean tank temperature recorded prior to the 

test draw oF. 

405 CALCULATION FOR DETERMINATION OF STORAGE TANK CAPACITY: Storage tank 

capacity is computed by the following equation:

Vst = (Wf - Wt)/Ds

Where : Vst = storage capacity of the water heater in gallons.

Wf = weight of the water heater completely filled with water in 

pounds.

Wt = weight of the empty water heater in pounds.

Ds = density of water at the appropriate temperature in 

pounds/gallon.

500 MONITORING AND RECORD KEEPING

501 TESTING PROCEDURE: 

501.1 Any natural gas-fired water heater, boiler or process heater distributed, offered for 

sale, sold, or installed within the District to which this rule applies shall be tested in 

accordance with the South Coast Air Quality Management District Protocol: Nitrogen 

Oxides Emissions Compliance Testing for Natural Gas-Fired Water Heaters and 

Small Boilers, as amended January 19958.

501.2 Any water heater, boiler or process heater fired with a fuel other than natural gas, to 

which this rule applies, shall be tested in accordance with the test methods below. 

All emission determinations shall be made while the unit is operating according to the 

manufacturer’s recommendations. Tests shall be conducted while the unit is

operating at a firing rate that is as close as physically possible to the unit’s 

recommended heat input capacity. Tests shall consist of three 40-minute sampling 

periods. Results shall be averaged over the three test periods. Test reports shall 

include the operational characteristics of all flue-gas NOx reduction equipment.

a. Oxides 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.

502 DURATION OF RECORDS: A manufacturer shall keep test reports and certification records 

for as long as the water heater, boiler or process heater model is offered for sale or sold in 
SACRAMENTO METROPOLITAN AQMD RULES AND REGULATIONS 

414-6 August 1, 1996XX-XX-2010

the District, or for three calendar years after manufacture, whichever is longer. These 

records shall be made available to the Air Pollution Control Officer upon request.