(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:

07/17/12) 

AVAQMD RULE 218 218-1

Continuous Emission Monitoring 

RULE 218 

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: 

(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 

(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. 

(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 subsystems (e.g., temperature, pressure, differential 
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Continuous Emission Monitoring 

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 subsystems (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 subsystem 

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. 

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

to a given gaseous compound concentration. A certified calibration gas mixture is 

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

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

calibrated according to the applicable requirements of Rule 218, and that has met 

the applicable performance specifications according to Rule 218 Section 

(D)(1)(b), and, has received written approval and conditions thereto applying, 

from the APCO. 

(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

(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. 
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Continuous Emission Monitoring 

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

emissions 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 

representative of the stack emissions for which the CEMS (or SCEMS) is 

required. 

(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. 

(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 APCO. Repairs to a malfunctioning system are 

excluded from this definition. 

(14) “Sampling Interface” – That part of the CEMS that performs 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. 

(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 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 

Interface, Analyzer and DAS. 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. 
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Continuous Emission Monitoring 

(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). 

(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.” 

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

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

(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. 

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

or Diluent Gas which, when periodically injected into the CEMS, is used to check 

CEMS response to the absence of the air contaminant or Diluent Gas. 

(C) Monitoring Requirements for New, Modified and Existing CEMS 

(1) The owner or operator of any equipment subject to this rule shall provide, 

properly install, operate and maintain in Calibration and good working order a 

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

of air contaminants and Diluent Gases, flow rates, and other required parameters. 

The owner or operator shall also provide the necessary records and other data 

necessary to calculate air contaminant emission rates or concentrations, as 

specified in Rule 218 Sections (F) and (G). 

(D) Requirements for New and Modified CEMS and SCEMS 

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

(a) 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 July 

17, 2012, 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 
AVAQMD RULE 218 218-5

Continuous Emission Monitoring 

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: 

(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, 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. 
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Continuous Emission Monitoring 

(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 limit(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 limit(s). 

(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; 

(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. 
AVAQMD RULE 218 218-7

Continuous Emission Monitoring 

(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 July 17, 2012 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 CEMS application for initial and final approval submitted to the APCO 

before July 17, 2012 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. 

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

written QA/QC Plan no later than July 17, 2013. The written QA/QC Plan 

shall be kept on record and available for inspection upon request by the 

APCO. 

(2) Requirements for Existing SCEMS 

(a) A SCEMS installed and granted final approval before July 17, 2012 shall 

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

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 July 17, 2012 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 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 July 

17, 2012 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 Appendices B and F, as 

applicable, when the equipment served by the Time-Shared 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 
AVAQMD RULE 218 218-9

Continuous Emission Monitoring 

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. 

(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 
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Continuous Emission Monitoring 

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 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. 

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

SCEMS 

The CEMS owner or operator of an approved CEMS shall affix a written notice of 

approval or a legible facsimile thereof upon the equipment or within 26 feet of the 

equipment as prescribed in Rule 206 – Posting Of Permit To Operate, in a manner such 

that it is clearly visible, 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. 

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