(Adopted: 1/ 9/76; Amended: 4/1/77; Amended: 8/5/77; Amended:

4/6/79; Amended: 8/7/81; Readopted by Statute: 07/01/97; 

Readopted by Statute: 01/01/02; Amended: 5/17/05; Amended:

mm/dd/yy) 

AVAQMD RULE 218 218-1

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RULE 218 

Stack Continuous Emission Monitoring 

(A) General 

(1) Purpose 

(a) The purpose of this rule is to specify Continuous Emission Monitoring 

System (CEMS) approvals and standards. 

(2) Applicability 

(a) The provisions of this rule shall apply to all sources that require CEMS as 

specified in the regulations or permit conditions, with the following 

exceptions: [Derived from SCAQMD Rule 218 §(b)(1).] 

(i) This rule shall not apply to CEMS subject to Regulation IX – 

Standards of Performance for New Stationary Sources, Regulation 

X – National Emissions Standards for Hazardous Air Pollutants, 

or Rule 3010 – Acid Rain Provisions of Federal Operating 

Permits. 

(ii) This rule shall not apply to CEMS subject to permit conditions 

where the purpose of the CEMS is to monitor the performance of 

the basic and/or control equipment and not to determine 

compliance with any applicable limit or standard. 

(iii) This rule shall not apply to CEMS where alternative performance 

specifications are required by another District rule. 

(B) Definitions 

[Relocated from former section (G). New definitions are from SCAQMD 

Rule 218 unless otherwise indicated.]

(1) “Analyzer” – The part of the CEMS that analyzes the appropriate gaseous 

constituents of the conditioned gaseous sample or measures stack gas volumetric 

flow and fuel flow rates, as applicable. 
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(a) Contaminant Analyzer – The part of the CEMS that detects the air 

contaminant and represents those concentrations in a signal output. 

(b) Diluent Analyzer – The part of the CEMS that detects oxygen, carbon 

dioxide or other Diluent Gas concentrations and represents those 

concentrations in a signal output. 

(c) Fuel Flowmeter – The part of the CEMS that detects the parameters of all 

essential measurement sub-systems (e.g., temperature, pressure, 

differential pressure, frequency, gas density, gas composition, heating 

value) and generates signal outputs which are a function of the fuel flow 

rate and all essential measurement subsystem parameters. 

(d) Stack Flowmeter – The part of the CEMS that detects the parameters from 

all essential measurement sub-systems (e.g., temperature, static and 

atmospheric pressure, gas density, gas composition, molecular weight, gas 

moisture content) and generates signal outputs which are a function of the 

stack gas volumetric flow rate and all essential measurement sub-system 

parameters. 

(2) “Calibration” – A procedure performed to ensure that the CEMS accurately 

measures and records air contaminant or Diluent Gas concentration, flow rate and 

other parameters necessary to generate data, as evidenced by Calibration Checks, 

and achieved by periodic manual or automatic adjustment.An operating condition 

of the monitoring system whereby the system is accurately recording the 

concentration of the specific air contaminant or diluent gas as evidenced by 

calibration checks, achieved by periodic manual or automatic adjustment. 

[Modified for consistency with SCAQMD Rule 218 definition.]

(3) “Calibration Check” – A procedure performed to determine the CEMS response of 

the systemto a given gaseous compound concentrationby means of injecting a 

certified calibration gas mixture into the system, or the insertion of a span cell into 

the internal light path of the analyzer. A certified calibration gas mixture is 

injected into the CEMS as close to the probe tip as practical. 

(3) Calibration Drift** - The change in the monitoring system output over a stated 

time period of normal continuous operation when the air contaminant or diluent 

gas concentration at the time of the measurements is the same known upscale 

value, or simulated to be the same upscale value by use of a span cell. 

(4) Calibration Error** - The difference between the air contaminant or diluent gas 

concentration indicated by the monitoring system and the known concentration of 

the span gas or the equivalent rating of the span cell. 

(4) “Certified CEMS” – A CEMS installed, tested, operated, maintained, and 

calibrated according to the applicable requirements of Rule 218, and that has met 
AVAQMD RULE 218 218-3

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the applicable performance specifications according to Rule 218 (D)(1)(b), and, 

has received written approval and conditions thereto applying, from the APCO. 

(5) Calibration Gas - A mixture of the air contaminant gas, or carbon dioxide or 

oxygen in a diluent gas, which, when periodically introduced into the monitoring 

system, is used to check that system's accuracy. 

(5) “Certified Gas Mixture” – A gas mixture manufactured, analyzed and certified

according to “EPA Traceability Protocol for Assay and Certification of Gaseous 

Calibration Standards” – EPA-600/R97/121, September 1997 Revision (EPA 

Protocol) or any subsequent version published by EPA. This definition 

incorporates by reference EPA Protocol. A mixture analyzed, by replicate 

samples, by the manufacturer by referring to National Bureau of Standards 

Reference Materials, such that a statement of the precision of the analysis can be 

made. [Modified for consistency with SCAQMD rule definition.] 

(6) “Continuous Emissions Monitoring System” (CEMS) – The total combined 

equipment and systems required to continuously determine air contaminants and 

Diluent Gas concentrations and/or mass emission rate of a source effluent (as 

applicable). The CEMS consists of three major subsystems: Sampling Interface, 

Analyzer, and Data Acquisition System. 

(7) “Continuous Monitoring” – Monitoring in which a minimum of one (1) 

measurement (e.g., concentration, mass emission, flow rate) is taken and recorded 

each minute. 

(8) “Data Acquisition System” (DAS) – The part of the CEMS that processes data 

generated by the Analyzer and records the results, thus creating a permanent 

record of the output signal in terms of concentration, flow rate, and/or any other 

applicable parameter necessary to generate the required data in units of applicable 

standard. The DAS consists of all equipment, such as a computer, required to 

convert the original recorded values to any values required for reporting. 

(9) “Diluent Gas” – A gas present in a calibration gas mixture or in the source 

emissions from a source which is present in quantities significantly larger than the 

air contaminant. 

(10) “Laboratory Approval Program” (LAP) – A program administered by the South 

Coast Air Quality Management District (SCAQMD) that grants test-methodspecific approvals to independent testing laboratories or firms that perform tests to 

determine source compliance with SCAQMD rules and regulations. 

(11) “Modification Requiring Recertification” – Any change to the basic equipment, 

control equipment, contaminant concentration, interfering substances, or CEMS 

(or SCEMS) that is deemed by the APCO to have a potential for adversely 

affecting the ability of the CEMS to provide accurate, precise and timely data 
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representative of the stack emissions for which the CEMS (or SCEMS) is 

required. 

(8) Ninety-Five Percent Confidence Interval - The statistically determined range 

within which there is a ninety-five percent (95%) probability all values determined 

will lie. 

(9) Operational Period - A minimum period of time during which the monitoring 

system shall operate, according to the performance and equipment specifications, 

without unscheduled maintenance, repair, or adjustment. 

(10) Parts Per Million - A volume concentration measurement, indicating the 

volumetric quantity of the gas in question, dispersed in one million volumes of gas 

mixture, reported on a dry basis. 

(12) “Quality Assurance/Quality Control (QA/QC) Plan” – A written document in 

which the specific procedures for the operation, Calibration, and maintenance of a 

Certified CEMS are described in detail, including additional quality assurance 

assessments and the corrective action system. The purpose of this plan is to 

ensure that the CEMS generates, collects, and reports valid data that is precise, 

accurate, complete, and of a quality that meets the requirements, performance 

specifications, and standards of Rules 218 and 218.1. 

(11) Reference Method - The official test method employed by the District to 

determine compliance with the rules. 

(12) Relative Accuracy - The degree of correctness with which the monitoring system 

yields the value of gas concentration of a sample relative to the value given by the 

reference method or to the allowed concentration. This accuracy is expressed in 

terms of error, which is the absolute value of the mean of the differences between 

the pared concentration measurements plus the absolute value of the ninety-five 

percent (95%) confidence interval. It is expressed as a percentage of the mean 

reference method value or of the allowed concentration. When a rule requires a 

correction of the air contaminant concentration to a specific O2 or CO2

concentration, the relative accuracy requirement shall apply to the corrected 

concentration value. 

(13) Response Time - The time interval from a step change in the air contaminant or 

gas diluent concentration at the input to the monitoring system to the time at 

which ninety-five percent (95%) of the corresponding final value is reached as 

displayed on the monitoring system data recorder. 

(13) “Routine Maintenance” – Preventive evaluation and repair (if necessary) of CEMS 

performed at specified intervals to preclude System Failure. Routine Maintenance 

may be performed as recommended by the manufacturer or a documented standard 

operating procedure determined through operating experience and approved by the 
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Executive OfficerAPCO. Repairs to a malfunctioning system are excluded from 

this definition.An operation, recommended by the manufacturer, to be performed 

at specified intervals, to preclude system failure. Repairs to a malfunctioning 

system are excluded from this definition. 

(15) Span Cell - A sealed cell of fixed length, containing a known concentration of an 

air contaminant, which is inserted into the internal light path of the analyzer to 

provide a measurement output that corresponds to a known concentration of that 

air contaminant. 

(16) Stack Monitoring System, or Monitoring System - The total equipment required 

for the determination of concentrations of air contaminants and diluent gases in a 

source effluent. The system consists of three major subsystems: 

(14) “Sampling Interface” –That part of the CEMS that performs one or more of the 

following operations: delineation, acquisition, transportation, and conditioning of 

a sample of the source effluent or protection of the analyzer from the hostile 

aspects of the sample or source environment. sample acquisition using one or 

more of the following operations: extraction, physical/chemical separation, 

transportation or conditioning of a representative sample from a designated 

source. 

(b) Analyzer 

(i) Air Contaminant Analyzer - that portion of the monitoring system 

that senses the air contaminant and generates a signal output that is 

a function of the concentration of that gas. 

(ii) Diluent Analyzer - that portion of the monitoring system that 

senses the concentration of oxygen or carbon dioxide and generates 

a signal output that is a function of the concentration of that gas. 

This subsystem is required only for sources noted in a (a)(1)(A). 

(c) Data Recorder - that portion of the monitoring system that provides a 

permanent record of the output signal in terms of concentration units, 

including additional equipment such as computers required to convert the 

original recorded value to any value required for reporting. [See (B)(1) and 

(B)(8).] 

(15) “Semi-Continuous Emission Monitoring” – A monitoring technique in which a 

minimum of one (1) measurement (e.g., concentration, mass emission, flow rate) 

is taken and recorded every fifteen (15) minutes. 

(16) “Semi-Continuous Emission Monitoring System” (SCEMS) – The total combined 

equipment and systems to semi-continuously determine air contaminant and 

Diluent Gas concentrations and/or the mass emission rate in a source effluent (as 

applicable). The system consists of three (3) major subsystems: Sampling 
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Interface, Analyzer and DASata cquisition ystem. This class of monitoring 

includes, but is not limited to, gas chromatography, integrated sensitized tape 

analyzer, other sample integration based technologies, and Time-Shared CEMS. 

(17) “South Coast Air Quality Management District” (SCAQMD) – The air quality 

district created pursuant to Division 26, Part 3, Chapter 5.5 of the California 

Health & Safety Code (commencing with §40400). [Derived from AVAQMD Rule 

1124.] 

(18) “System Failure” – Inability of the CEMS to meet the requirements of Rule 218.1 

– Continuing Emission Monitoring Performance Specifications, or, Code of 

Federal Regulations, Title 40 – “Protection of Environment,” Part 60 – “Standards 

of Performance for New Stationary Sources,” Appendix F – Quality Assurance 

Procedures.”occurs anytime the monitoring system is suspected or known to be 

unable to meet the requirements of (c)(2) or (b)(2), as applicable. 

(19) “Time- Sharing” – A monitoring technique where an Analyzer, and possibly the 

associated sampling conditioning system, is used on more than one source. 

(18) Use Factor - The amount of time used per year divided by the amount of time 

available for use per year, expressed as a percent.

(20) “Working Day” – Monday through Friday, excluding holidays. 

(21) “Zero Check” – A procedure performed to determine the response of the CEMS to 

a given Zero Gas standard by means of injecting the Zero Gas into the CEMS as 

close to the probe tip as practical. 

 (19) Zero Calibration Reflector - A device which is inserted into the internal light path 

of the analyzer to provide a measurement output that simulates a zero gas 

concentration. 

(20) Zero Drift** - The change in the monitoring system over a stated period of time of 

normal continuous operation when the air contaminant or diluent gas 

concentration at the time of the measurements is zero, or is simulated to be zero 

by use of a zero calibration reflector. 

(22) “Zero Gas” – A gas containing less than a specified amount of the air contaminant 

or Diluent Gas which, when periodically injected into the CEMSmonitoring 

system, is used to check CEMS that system's response to the absence of the air 

contaminant or Diluent Gas. 

 *The operational period test performed prior to final approval shall be preceded by 

a one hundred sixty eight (168) hour (minimum) conditioning period during which 

the system shall be operated without unscheduled maintenance, repair, or 

adjustment. 
AVAQMD RULE 218 218-7

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 **Expressed as the sum of the mean value plus the ninety-five percent (95%) 

confidence interval of a series of tests. 

(AC) Stack Monitoring Requirements for New, Modified and Existing CEMS

(1) The owner or operator of any equipment described belowsubject to this rule shall 

provide,; properly install, operate and maintain in calibrationCalibration and, in

good working order and in operation; approved stack monitoring systemsa 

Certified CEMS to measure the concentration and/or emission rates, as applicable, 

of the following air contaminants and diluent Diluent gasesGases, flow rates, and 

other required parameters in the emissions from the sources indicated. The owner 

or operator shall also provide the necessary records and any other data necessary 

for to calculateing air contaminant emission rates or concentrations, as specified in 

Rule 218 Sections (F) and (G). 

 (a) Oxides of nitrogen (NOx), and carbon dioxide (CO2) or oxygen (02), from 

steam generators with a heat input of 63 million kilogram calories (250 

million British Thermal Units) or more per hour and with a use factor of at 

least thirty percent (30%). 

(b) Sulfur dioxide (SO2) from steam generators with a heat input of 63 million 

kilogram calories (250 million British Thermal Units) or more per hour 

and with a use factor of at least thirty percent (30%) if control equipment is 

used. 

(c) Oxides of nitrogen (NOx) from all nitric acid production plants. 

(d) Gaseous sulfur compounds calculated as sulfur dioxide (SO2) from all 

sulfuric acid production plants, carbon monoxide boilers or furnaces of the 

regenerators of fluid catalytic cracking units, and all fluid cokers. 

(e) Sulfur dioxide (SO2) from sulfur recovery plants with oxidizing tail gas 

units, and with reducing tail gas units using continuous incineration for 

control of hydrogen sulfide (H2S). 

(2) The Air Pollution Control Officer (APCO) may require a person to provide, 

properly install, maintain in calibration, in good working order and in operation, 

an approved stack monitoring system to measure air contaminants in emission 

gases when that person installs, operates, or uses any equipment which emits 

900,000 kilograms (992 tons) or more per year of carbon monoxide (CO) or 

90,000 kilograms (99 tons) or more per year of any air contaminant except carbon 

monoxide (CO). The APCO shall report to the District Board in writing when he 

requires the installation of a stack monitoring system under the provisions of this 

subpart.
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(BD) Requirements for New and Modified CEMS and SCEMS 

(1) Application and Approval Requirements of for New and Modified CEMS 

Monitoring Systems

(1a) The owner or operator of any equipment subject to this Rule shall submit 

to the APCO an “Application for CEMS” or “Application for CEMS 

Modification”, as applicable. Any application submitted on or after [date 

of amendment], shall require an initial approval by the APCO prior to 

installation of a new CEMS or modification of an existing CEMS. The 

APCO shall notify the applicant in writing within 60 calendar days of 

receipt of an application for a new CEMS, or within 30 calendar days of 

receipt of an application for a modification to an existing CEMS, if the 

application contains sufficient information to be deemed complete. Where 

an application has been determined to be incomplete, the APCO shall 

request specific information needed to complete the application. Upon 

receipt of any complete resubmittal or the additional information, plans or 

specifications after the application has been deemed incomplete, a new 30-

day period shall begin during which the APCO shall determine the 

completeness of the application and notify the applicant. Within 90 days 

of installation, a person operating or using CEMS shall undertake a series 

of certification tests. If the equipment served by the CEMS is not 

operating at the time of complete CEMS installation, then the CEMS shall 

undergo a series of certification tests within 90 days from the next start-up 

of the equipment served by the CEMS. The purpose of the certification 

tests is to demonstrate the CEMS performance pursuant to the 

specifications in accordance with the provisions of Rule 218, Section 

(D)(1)(b). The owner or operator shall notify the APCO in writing at least 

14 days before the scheduled certification test dates. The certification tests 

shall be performed by a testing laboratory approved under the SCAQMD 

LAP. Data from such tests shall be submitted to the APCO within 45 days 

following test completion. If satisfactory performance is demonstrated, 

final approval of the CEMS shall be granted. Subsequent operation and 

maintenance of the Certified CEMS shall be in accordance with the 

provisions of Rule 218, Section (D)(1)(b). After final approval, 

modifications made to the CEMS shall be reviewed and approved by the 

APCO according to the specifications stipulated in Rule 218, Section 

(D)(1)(b), and may require all or a portion of performance tests to be 

conducted. 

(b) Upon submission of an “Application for CEMS” or “Application for 

CEMS Modification” as prescribed in Rule 218 Section (D)(1)(a), the 

applicant shall indicate either one of the following conditions: 
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(i) That the CEMS shall be reviewed and certified according to the 

provisions of Rule 218.1 - , “Continuous Emission Monitoring 

Performance Specifications”, Section (C), and the subsequent 

operation and maintenance of the Certified CEMS shall be in 

accordance with the provisions of Rule 218, Sections (C), (F), (G) 

and (H) and of the requirements of Rule 218.1 Sections (C) and 

(E); or, 

(ii) That the CEMS shall be reviewed and certified according to the 

applicable provisions of the Code of Federal Regulations, Title 40 

– “Protection of Environment”, Part 60 – “Standards of 

Performance for New Stationary Sources” (40 CFR 60), Appendix 

B – “Performance Specifications” (Appendix B), and the 

subsequent operation and maintenance of the Certified CEMS shall 

be in accordance with the provisions of Rule 218, Sections (C), (F), 

(G) and (H), and the requirements of 40 CFR 60, Appendix F – 

“Quality Assurance Procedures” (Appendix F). Notwithstanding 

the requirements of this Section (c)(1)(B)(ii), any alternative test 

methods for 40 CFR 60, Appendices B and F shall be those that are 

listed in Rule 218.1, Table 1 - Reference Methods. 

(c) A “Notification of Pre-Approved Modification” and report of results of 

prescribed quality assurance checks may be submitted in lieu of the 

“Application for CEMS Modification” when the modification has been 

made in accordance with the written technical guidance document 

approved by the APCO. 

(2) Application and Approval Requirements for New and Modified SCEMS 

(a) In- lieu of submitting an application for CEMS per Rule 218, Section 

(D)(1), the owner or operator of any equipment subject to this Rule, may 

elect to submit an application for a SCEMS if the averaging time for the 

applicable limits(s) for which the CEMS is required is 24 hours or greater; 

or, if the owner or operator demonstrates, to the satisfaction of the APCO, 

that no CEMS technology is commercially available for the applicable 

contaminant and the applicable limits. 

(b) If the conditions in Rule 218, Section (D)(2)(a), above, do not apply, the 

owner or operator of any equipment subject to this Rule may still elect to 

submit an application for a SCEMS in lieu of a CEMS, subject to the 

following: 

(i) The owner or operator demonstrates that the concentrations and/or 

emissions required to be monitored would be equivalent to that 

monitored by a CEMS for the applicable averaging period, to the 

satisfaction of the APCO; 
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(ii) The SCEMS shall be capable to take and record a minimum of one

(1) measurement (concentration, mass emission rate and/or flow 

rate, as applicable) every 15 minutes allowing as equally spaced 

data points as practical; 

(iii) The owner or operator shall include in the QA/QC plan the method 

of calculating the 15-minute averages for compliance determination 

to the applicable limit or standard; 

(iv) If an exceedance of the allowable limit or standard is calculated 

using fewer than 100 percent% valid data points, then the District 

shall use any relevant data for the operation of the equipment (basic 

and control, as applicable) to verify the calculated exceedance; and 

(v) If a Time -Shared SCEMS is proposed, it shall meet the 

performance specifications of Rule 218.1, Section (F). 

(c) The requirements for the application submittal and approval of CEMS as 

provided in Rule 218, Section (D)(1) shall also apply for SCEMS 

applications. 

(3) Operation of CEMS or SCEMS During Certification Testing 

CEMS or SCEMS shall be certified as configured for the normal operation of the 

CEMS or SCEMS with respect to sample acquisition, sample conditioning, 

pollutant/diluent detection, data requirements and reporting. 

(4) QA/QC Plan for New or Modified CEMS or SCEMS 

(a) The owner or operator of CEMS or SCEMS who elects the performance 

specifications according to Rule 218, Section (D)(1)(b)(i), shall submit to 

the APCO for approval a CEMS QA/QC Plan within 45 days of CEMS 

installation and no later than 30 days before the certification tests. 

(b) Alternative Quality Assurance Practices 

The owner or operator of CEMS or SCEMS who elects the performance 

specifications according to Rule 218, Section (D)(1)(b)(i), may choose to 

develop alternative CEMS operational test requirements to be included in 

the CEMS QA/QC procedures that assure data of equivalent or better 

quality. These alternative QA/QC procedures shall be submitted with the 

facility QA/QC Plan and are subject to the approval of the APCO. 

(E) Requirements for Existing CEMS and SCEMS 

(1) Requirements for Existing CEMS 

(a) A CEMS installed and granted final approval before May 14, 1999[date of 

rule amendment] shall be maintained and operated according to the 
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provisions of Rule 218, Sections (C), (F), (G) and (H), and the 

requirements of Rule 218.1, Sections (D) and (E). 

(b) A CEMS application for initial and final approval submitted to the APCO 

before May 14, 1999[date of rule amendment] shall be reviewed and 

approved by the APCO according to the specifications and requirements of 

Rule 218.1, Sections (D) and (E). After final approval, the CEMS shall be 

operated and maintained according to the provisions of Rule 218, Sections 

(C), (F), (G) and (H), and the requirements of Rule 218.1, Sections (D) and 

(E). 

(c) Modifications Requiring Recertification to any existing CEMS shall be 

reviewed and approved according to the conditions under Rule 218 Section 

(D)(1)(b)(i) or (ii), as applicable. After final approval, the modified 

CEMS shall be operated and maintained according to the conditions under 

Rule 218, Section (D)(1)(b)(i) or (ii), as applicable. 

(di) All existing CEMS as prescribed in Rule 218, Sections (E)(1)(a) and (b) 

shall comply with the provisions of Rule 218.1, Sections (C) and (DE), or 

40 CFR 60 Appendices B and F, as applicable, and of Rule 218, Sections 

(C) and (D), no later than May 14, 2006[seven (7) years from date of rule 

amendment]. [Typographical error corrected pursuant to EPA comment of 

04/25/12. There is only one facility in the District with an existing CEMS 

currently subject to the provisions of this rule. This facility has indicated 

that they are compliant with the provisions of the rule and the additional 

time provision is not necessary. Removed in response to EPA comment 

1b of 04/25/12.] 

(iie) The requirements of Rule 218, Section (E)(1)(d)(i) shall be waived for a 

period of three (3) years if the owner or operator demonstrates, to the 

satisfaction of the Executive OfficerAPCO, that the existing CEMS is 

providing data that areis of a quality commensurate with the original 

performance specifications and other indicators of consistent data quality. 

Data quality factors that will be considered include: 

(i) Relative Accuracy; 

(ii) Calibration Error; 

(iii) Calibration Drift; 

(iv) Zero Drift; 

(v) Valid data return percentage; 

(vi) Availability or up-time percentage; 

(vii) Breakdown frequency and duration; and 

(viii) Excursions beyond quality control limits in QA/QC plan. 
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The owner or operator may apply for a waiver under this subsection every three (3) years after May 14, 2006[Seven (7) years 

from date of rule amendment]. This subsection shall not apply to 

existing CEMS that are required to comply with the provisions of 

Rule 218.1, Sections (C) and (E), or, 40 CFR 60, Appendices B 

and F, as applicable, and Rule 218, Sections (C) and (D), as a result 

of CEMS Modifications Requiring Recertification, rule 

implementation, or, compliance with a permit condition.[There is 

only one facility in the District with an existing CEMS currently 

subject to the provisions of this rule. This facility has indicated 

that they are compliant with the provisions of the rule and the 

additional time provision is not necessary. Removed in response to 

EPA comment 1b of 04/25/12.] 

(efd) The owner or operator of existing CEMS shall develop and implement a 

written Quality Assurance/ Quality Control (QA/QC) Plan no later than 

May 14, 2000[one (1) year from date of rule amendment]. The written 

QA/QC Plan shall be kept on record and available for inspection upon 

request by the APCO. 

(fg) On or before May 14, 2005[Six (6) years from date of rule amendment], 

the owner or operator of any existing CEMS shall submit to the APCO for 

approval: 

(i) A certification signed by an authorized representative of the facility 

that the existing CEMS meets the requirements of Rule 218, 

Section (D); 

(ii) An “Application for CEMS Modification”, with the applicable 

fee(s) as specified in Rule 301; or 

(iii) An application for waiver according to Rule 218, Section (E)(1)(d), 

with documentation supporting the required demonstration. [There 

is only one facility in the District with an existing CEMS currently 

subject to the provisions of this rule. This facility has indicated 

that they are compliant with the provisions of the rule and the 

additional time provision is not necessary. Removed in response to 

EPA comment 1b of 04/25/12.]

(2) Requirements for Existing SCEMS 

(a) A SCEMS installed and granted final approval before May 14, 1999 [Date 

of rule amendment] shall be maintained and operated according to the 

provisions of Rule 218, Sections (C), (F), (G) and (H), and the 

requirements of Rule 218.1, Sections (D) and (E). 

(b) A SCEMS application for initial and final approval submitted to the APCO 

before May 14, 1999 [Date of rule amendment] shall be reviewed and 
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approved by the APCO according to the specifications and requirements of 

Rule 218.1, Sections (D) and (E). After final approval, the SCEMS shall 

be operated and maintained according to the provisions of Rule 218, 

Sections (C), (F), (G) and (H), and the requirements of Rule 218.1, 

Sections (D) and (E). 

(c) Modifications Requiring Recertification to any existing SCEMS shall be 

reviewed and approved according to the conditions under Rule 218 Section 

(D)(1)(b)(i) or (ii), as applicable. After final approval, the modified 

CEMS shall be operated and maintained according to the conditions under 

Rule 218, Section (D)(1)(b)(i) or (ii), as applicable. 

(d) The owner or operator of an existing SCEMS operating on or before May 

14, 1999 [Date of rule amendment] shall be required to comply with the 

provisions of Rule 218.1 Section (F) - “Time -Sharing Requirements” and 

with the provisions of Rule 218.1 Sections (C) and (E), or, 40 CFR 60 

Appendix B and F, as applicable, when the equipment served by the TimeShared SCEMS is modified such that: 

(i) One or more of the sources monitored requires a new monitoring 

range; 

(ii) The operating permit is modified to require Continuous 

Monitoring; or, 

(iii) An applicable source specific rule is adopted or revised to require 

Continuous Monitoring. 

Subsequent operation and maintenance of the SCEMS shall be 

according to the provisions of Rule 218, Section (D)(1)(b)(i) or (ii), 

as applicable. 

(F) Retention of Records for New, Modified and Existing CEMS and SCEMS 

(1) The records of the data obtained from the CEMS recording devices shall clearly 

indicate concentrations or emission rates, or both, as specified by the APCO. 

Records shall be maintained by the CEMS owner or operator for a minimum 

period of five (5) years, unless otherwise specifically provided by another District 

regulation or permit conditions, and, shall be made available to the APCO upon 

request. 

(2) All calculations, raw parameter data used for calculations, records of the 

occurrence and duration of any start up, shutdown or malfunction, performance 

test, evaluation, Calibration, adjustment and maintenance of the CEMS as well as 

calibration gas traceability shall be retained by the CEMS operator for a minimum 

period of five (5) years unless otherwise specifically provided by another District 
218-14 AVAQMD RULE 218 

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regulation or permit conditions, and shall be made available to the APCO upon 

request. 

(G) Reporting Requirements for New, Modified and Existing CEMS and 

SCEMS 

Unless otherwise specifically provided by another District regulation or permit 

conditions, the following reporting requirements shall apply to new, modified and 

existing CEMS and SCEMS: 

(1) A CEMS owner or operator shall provide a summary of the concentration and/or 

emission rate data, as applicable, obtained from the CEMS, as well as any 

additional information specified by the APCO, to evaluate the accuracy and 

precision of the measurements. The summary shall be submitted once every six 

(6) months to the APCO, except when more frequent reporting is specifically 

required by another District rule, or the APCO, on a case-by-case basis, 

determines that more frequent reporting is necessary to accurately assess the 

compliance status of the source. The summary report shall be submitted within 30 

days following the end of the six (6)-month period being reported, in the form and 

manner prescribed by the APCO. The summary shall be maintained on-site in a 

retrievable and readable form and shall be made available to the APCO upon 

request. The submitted summaries shall be available for public inspection at the 

District. 

(2) The CEMS owner or operator shall report any concentration level and/or emission 

rate, as applicable, in excess of the regulated limit within 24 hours or the next 

Working Day after such occurrence in the form and manner prescribed by the 

APCO. The report shall include the following information: 

(a) Time intervals, date, and magnitude of the excess concentration level, 

nature and cause of the excess concentration (if known), corrective 

action(s) taken, preventive measure(s) adopted, specific location of CEMS, 

the equipment or CEMS involved and the facility contact person. 

(b) The averaging period used for data reporting shall correspond to the 

averaging period specified in the rule or permit condition governing the 

concentration and/or emission rate, if applicable. 

(3) Reports of CEMS Failure or Shutdown 

(a) The CEMS owner or operator shall notify the APCO within 24 hours or 

the next Working Day, in the event of a system failure or shutdown, which 

exceeds 24 hours. Zero and Calibration Checks and Routine Maintenance 

do not require reporting. 
AVAQMD RULE 218 218-15

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(b) In the case of a CEMS failure or shutdown, compliance with the provisions 

of Rule 218, Section (C) is waived for a period not to exceed 96 

consecutive hours. Such waiver is extended beyond 96 consecutive hours 

only if a petition for an interim variance is filed in accordance with 

Regulation V – Procedures Before the Hearing Board and shall terminate 

at the time the Hearing Board acts upon such variance petition. CEMS 

owners or operators of qualified facilities may obtain a Hearing Board 

approval of an alternative operating condition following the established 

procedure in District Rule 518.2 - Federal Alternative Operating 

Conditions. 

(c) Regularly scheduled CEMS maintenance shall be deferred until the report 

required under Rule 218, Section (G)(2) is made, if the system is 

measuring a concentration equal to or exceeding the emission standard, 

and if such deferral is not reasonably expected to result in damage to the 

system. 

(d) Continuous emission monitoring requirements shall not apply during 

regular Calibration Checks of the system, or Routine Maintenance and 

repair lasting 60 minutes or less. 

All monitoring systems to be installed after April 6, 1979, require an initial 

approval by theAPCO, prior to installation. The APCO shall act upon an 

application for initial approval within 30 days after filing or within thirty 

(30) days after the applicant furnishes further information, plans and 

specifications requested to complete an application. Upon completion of 

installation, a person operating or using a stack monitoring system shall 

undertake a series of tests to demonstrate the acceptability of the system's 

performance pursuant to (C) below. Within six (6) months of initial 

operation, data from such tests shall be submitted to the APCO for 

approval. If satisfactory performance is demonstrated, a final approval of 

the system shall be granted.

(2) A person operating a monitoring system installed on or before April 6, 

1979, shall, by June 1, 1979, submit a plan to the APCO outlining steps to 

achieve compliance with the performance specifications of (C) below as 

expeditiously as practicable, but in no event later than March 2, 1981. 

Each plan shall include, but shall not necessarily be limited to, dates and 

methods for achieving the following increments of progress: 

1. Submit test results. 

2. Negotiate and sign contracts. 

3. Commence modification or replacement of non-complying 

systems. 
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4. Complete modification or replacement of non-complying systems. 

5. Submit final test results. 

6. Achieve final compliance with (C) below on or before 

March 2, 1981. 

Non-complying systems shall be operated at the level of performance 

indicated by test results. Each system shall be operated in accordance with 

the plan.

(3H) Posting of Written Approval for New, Modified and Existing CMS and 

SCEMS 

A person operating an approved monitoring systemThe CEMS owner or operator of an 

approved CEMS shall affix such a written notice of approval or a legible facsimile thereof 

upon the equipment or within 26 feet of the equipment as prescribed in District Rule 206,

in a manner such that it is clearly visible, and legible, and safely accessible. In the event 

that the equipment is so constructed or operated that the notice of approval or its legible 

facsimile cannot be so placed, such notice or legible facsimile shall be mounted on a 

location approved by the APCO. 

(C) Monitoring System Standards 

(1) The monitoring system shall be installed at a location such that air contaminant 

and diluent gas concentration measurements can be made which are representative 

of the stack emissions of the affected facility. 

(2) Prior to final approval of the monitoring system, it shall meet, and it shall 

thereafter be operated in accordance with, the following performance and 

equipment specifications:

 (a) Monitors for Gaseous Air Contaminants 
AVAQMD RULE 218 218-17

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Parameter Specifications 

(i) Operational Period* Greater than or equal to 168 hours. 

(ii) Calibration Error** Less than or equal to 5 percent. 

(iii) Response Time Less than or equal to 10 minutes. 

(iv) Zero Drift (2-hour)** Less than or equal to 2 percent of full scale 

reading. 

(v) Zero Drift**(24-hour) Less than or equal to 2 percent of full scale 

reading. 

(vi) Calibration Drift (2-hour)** Less than or equal to 2 percent of scale 

reading. 

(vii) Calibration Drift (24-hour)** Less than or equal to 2.5 percent of full scale 

reading. 

(viii) Relative Accuracy** Less than or equal to 20 percent of the mean 

value of the reference method test data or less 

than or equal to 10 percent of the allowed 

concentration, whichever is greater. 

(b) Monitors for Diluent Gases 

Parameter Specifications 

(i) Operational Period* Greater than or equal to 168 hours. 

(ii) Calibration Error** Less than or equal to 5 percent. 

(iii) Response Time Less than or equal to 10 minutes. 

(iv) Zero Drift (2-hour)** Less than or equal to 0.4 percent CO2 or 02. 

(v) Zero Drift (24-hour)** Less than or equal to 0.5 percent CO2 or 02. 

(vi) Calibration Drift (2-hour)** Less than or equal to 0.4 percent CO2 or 02. 

(vii) Calibration Drift (24-hour)** Less than or equal to 0.5 percent CO2 or 02. 

(3) The monitoring system shall be operated according to the following standards: 

(a) Calibration gases shall meet the following criteria: 

(i) For gaseous air contaminant monitors, the mixture shall be certified 

to be within two percent (2%) of the stated value. 

(ii) For carbon dioxide and oxygen monitors, the mixture shall be 

certified to be within two-tenths percent (0.2%) carbon dioxide or 

oxygen of the stated value. Ambient air may be used for oxygen 

monitors if the span is higher than twenty one percent (21%) 

oxygen. 

(b) Zero gases used shall meet the following criteria: 

(i) For gaseous air contaminant monitors, the gas shall be certified by 

the manufacturer to contain less than 1 part per million of the air 
218-18 AVAQMD RULE 218 

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contaminant (except carbon monoxide, less than 10 parts per 

million), or alternately, ambient air may be used. 

(ii) For carbon dioxide and oxygen monitors, the gas shall be certified 

by the manufacturer to contain less than 100 parts per million of 

carbon dioxide or oxygen. 

(c) Calibration gases shall be manufactured, analyzed and certified according 

to USEPA Traceability Protocol for Assay and Certification of Gaseous 

Calibration Standards (EPA-600/R97/121) as revised September 1997 or 

any subsequent version as published by USEPA 

(d) Calibration checks shall be performed at least once each day at regular 

intervals. 

(e) The instrument full scale reading shall be equivalent to approximately two 

hundred percent (200%) of the concentration limit specified in the 

applicable rule, or at a value approved by theAPCO. Oxygen and carbon 

dioxide instruments full scale readings shall be such that the full range of 

concentrations encountered can be measured. 

(f) Regular scheduled maintenance of the monitoring system shall be deferred 

until the report required under Section (E)(2) is made, if the system is 

measuring a concentration equal to or exceeding the emission standard, 

and if such deferral will not reasonably be expected to result in damage to 

the system. 

(g) The monitoring system shall complete a minimum of one cycle of 

operation (sampling, analyzing, and data recording), for each successive 

fifteen (15) minute period. 

(h) The requirements of section (C)(3)(g) shall not apply to the following 

conditions: 

(i) Regular calibration checks of the system. 

(ii) Routine maintenance and repair of sixty (60) minutes or less 

duration. 

(4) Following final approval, if significant modifications are made to the system, a 

demonstration of the ability of the system to operate in accordance with the 

specifications of (c)(2) may be required at the discretion of the Executive Officer. 

(5) Span cell calibration techniques may be employed with in situ monitors, not 

extracting the gas sample from the stack if the criteria of (c)(2)(A)(ii), (vi) and 

(vii) can be met and if the use of the cell provides a check of all analyzer internal 

mirrors and lenses and all electronic circuitry including the source and detector 

assembly which are normally used in sampling and analysis. 
AVAQMD RULE 218 218-19

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(6) Zero calibration reflector techniques may be employed with in situ monitors, not 

extracting the gas sample from the stack, if the criteria of (c)(2)(A)(iv) and (v) can 

be met. 

(D) Retention of Records 

(1) The records of the data obtained from the recording devices of the stack 

monitoring system shall clearly indicate concentrations as specified by theAPCO. 

Records shall be maintained by the owner or operator of a monitoring system for a 

period of at least two (2) years and shall be made available to the APCO upon 

request. 

(2) All records of the occurrence and duration of any start up, shutdown or 

malfunction, performance test, evaluation, calibration, adjustment and 

maintenance of the monitoring system as well as calibration gas traceability or 

span cell specifications documents, shall be retained by the monitoring system 

operator for a period of at least two (2) years and shall be made available to the 

APCO upon request. 

(E) Reporting 

(1) A person operating a stack monitoring system shall provide a summary of the 

concentration and emission data obtained from such system, as well as any 

additional information specified by the APCO to evaluate the accuracy and 

precision of the measurements. The summary shall be submitted monthly to the 

APCO within thirty (30) days of the end of the month being reported, in the form 

and manner prescribed by him. The summary shall be available for public 

inspection at the office of the Air Quality Management District. 

(2) A person operating a monitoring system shall report any concentration level in 

excess of the regulated limit to the APCO within ninety-six (96) hours after such 

occurrence in the form and manner prescribed by him. The report shall include 

the following information: 

(a) Time intervals, date, and magnitude of the excess concentration level; 

nature and cause of the excess (if known), corrective actions taken and 

preventive measure adopted. 

(b) Averaging period used for data reporting shall correspond to the averaging 

period specified in the rule governing the concentration limit in question. 

(3) Reports of Monitoring System Failure or Shutdown 

(a) A person operating a monitoring system shall notify the Executive Officer 

within ninety-six (96) hours, in a form and manner prescribed by him, in 
218-20 AVAQMD RULE 218 

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the event of a system failure or shutdown for repair, which exceeds sixty 

(60) consecutive minutes. Zero and calibration checks and routine 

maintenance do not require reporting. 

(b) In the case of a monitoring system failure or shutdown for repair, 

compliance with the provisions of subsection (a) is waived for a period not 

to exceed ninety-six (96) consecutive hours. Such waiver is extended 

beyond ninety-six (96_ consecutive hours only if a petition for an interim 

variance is filed in accordance with Regulation V and shall terminate at the 

time the Hearing Board acts upon such variance petition. 

(F) Exemption 

Any source subject to the provisions of (a)(1) above may obtain an exemption from the 

provisions of (a)(1) above upon demonstration to the satisfaction of the APCO that the 

source is not subject to a District rule or regulation prohibiting or limiting the discharge of 

any air contaminants which are the subject of (a)(1). 

(G) Definitions 

(1) Calibration - An operating condition of the monitoring system whereby the system 

is accurately recording the concentration of the specific air contaminant or diluent 

gas as evidenced by calibration checks, achieved by periodic manual or automatic 

adjustment. 

(2) Calibration Check - A procedure to determine the response of the system to a 

given gaseous compound concentration by means of injecting a certified 

calibration gas mixture into the system, or the insertion of a span cell into the 

internal light path of the analyzer. 

(3) Calibration Drift** - The change in the monitoring system output over a stated 

time period of normal continuous operation when the air contaminant or diluent 

gas concentration at the time of the measurements is the same known upscale 

value, or simulated to be the same upscale value by use of a span cell. 

(4) Calibration Error** - The difference between the air contaminant or diluent gas 

concentration indicated by the monitoring system and the known concentration of 

the span gas or the equivalent rating of the span cell. 

(5) Calibration Gas - A mixture of the air contaminant gas, or carbon dioxide or 

oxygen in a diluent gas, which, when periodically introduced into the monitoring 

system, is used to check that system's accuracy. 
AVAQMD RULE 218 218-21

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(6) Certified Gas Mixture - A mixture analyzed, by replicate samples, by the 

manufacturer by referring to National Bureau of Standards Reference Materials, 

such that a statement of the precision of the analysis can be made. 

(7) Diluent Gas - A gas present in a calibration gas mixture or in the emissions from a 

source which is present in quantities significantly larger than the air contaminant. 

(8) Ninety-Five Percent Confidence Interval - The statistically determined range 

within which there is a ninety-five percent (95%) probability all values determined 

will lie. 

(9) Operational Period - A minimum period of time during which the monitoring 

system shall operate, according to the performance and equipment specifications, 

without unscheduled maintenance, repair, or adjustment. 

(10) Parts Per Million - A volume concentration measurement, indicating the 

volumetric quantity of the gas in question, dispersed in one million volumes of gas 

mixture, reported on a dry basis. 

(11) Reference Method - The official test method employed by the District to 

determine compliance with the rules. 

(12) Relative Accuracy - The degree of correctness with which the monitoring system 

yields the value of gas concentration of a sample relative to the value given by the 

reference method or to the allowed concentration. This accuracy is expressed in 

terms of error, which is the absolute value of the mean of the differences between 

the pared concentration measurements plus the absolute value of the ninety-five 

percent (95%) confidence interval. It is expressed as a percentage of the mean 

reference method value or of the allowed concentration. When a rule requires a 

correction of the air contaminant concentration to a specific O2 or CO2

concentration, the relative accuracy requirement shall apply to the corrected 

concentration value. 

(13) Response Time - The time interval from a step change in the air contaminant or 

gas diluent concentration at the input to the monitoring system to the time at 

which ninety-five percent (95%) of the corresponding final value is reached as 

displayed on the monitoring system data recorder. 

(14) Routine Maintenance - An operation, recommended by the manufacturer, to be 

performed at specified intervals, to preclude system failure. Repairs to a 

malfunctioning system are excluded from this definition. 

(15) Span Cell - A sealed cell of fixed length, containing a known concentration of an 

air contaminant, which is inserted into the internal light path of the analyzer to 

provide a measurement output that corresponds to a known concentration of that 

air contaminant. 
218-22 AVAQMD RULE 218 

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(16) Stack Monitoring System, or Monitoring System - The total equipment required 

for the determination of concentrations of air contaminants and diluent gases in a 

source effluent. The system consists of three major subsystems: 

(a) Sampling Interface - that portion of the monitoring system that performs 

one or more of the following operations: delineation, acquisition, 

transportation, and conditioning of a sample of the source effluent or 

protection of the analyzer from the hostile aspects of the sample or source 

environment. 

(b) Analyzer 

(i) Air Contaminant Analyzer - that portion of the monitoring system 

that senses the air contaminant and generates a signal output that is 

a function of the concentration of that gas. 

(ii) Diluent Analyzer - that portion of the monitoring system that 

senses the concentration of oxygen or carbon dioxide and generates 

a signal output that is a function of the concentration of that gas. 

This subsystem is required only for sources noted in a (a)(1)(A). 

(c) Data Recorder - that portion of the monitoring system that provides a 

permanent record of the output signal in terms of concentration units, 

including additional equipment such as computers required to convert the 

original recorded value to any value required for reporting. 

(17) System Failure - occurs anytime the monitoring system is suspected or known to 

be unable to meet the requirements of (c)(2) or (b)(2), as applicable. 

(18) Use Factor - The amount of time used per year divided by the amount of time 

available for use per year, expressed as a percent.

(19) Zero Calibration Reflector - A device which is inserted into the internal light path 

of the analyzer to provide a measurement output that simulates a zero gas 

concentration. 

(20) Zero Drift** - The change in the monitoring system over a stated period of time of 

normal continuous operation when the air contaminant or diluent gas 

concentration at the time of the measurements is zero, or is simulated to be zero 

by use of a zero calibration reflector. 

(21) Zero Gas - Agas containing less than a specified amount of the air contaminant or 

diluent gas which, when periodically injected into the monitoring system, is used 

to check that system's response to the absence of the air contaminant or diluent 

gas. 
AVAQMD RULE 218 218-23

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 *The operational period test performed prior to final approval shall be preceded by 

a one hundred sixty eight (168) hour (minimum) conditioning period during which 

the system shall be operated without unscheduled maintenance, repair, or 

adjustment. 

 **Expressed as the sum of the mean value plus the ninety-five percent (95%) 

confidence interval of a series of tests. 

[SIP: Approved 7/6/82, 47 FR 29231, 40 CFR 52.220(c)(103)(xviii)(A); Approved 9/28/81, 

46 FR 47451, 40 CFR 52.220(c)(65)(ii); Approved ________, _________, 40 CFR 

52.220(c)(42)(xiv)(A); Approved 9/8/78, 43 FR 40011, 40 CFR 52.220(c)(39)(iii)(C)]

See SIP Table at http://www.avaqmd.ca.gov/Modules/ShowDocument.aspx?documentid=921