(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)

AVAQMD RULE 218 218-1

Stack Monitoring

RULE 218

Stack Monitoring

(A) Stack Monitoring Requirements

(1) The owner or operator of any equipment described below shall provide; properly 

install, maintain in calibration, in good working order and in operation; approved stack 

monitoring systems to measure the concentration of the following air contaminants and 

diluent gases in the emissions from the sources indicated. The owner or operator shall 

also provide any other data necessary for calculating air contaminant emission rates.

(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.

(B) Approval of Monitoring Systems
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(1) 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.

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.

(3) A person operating an approved monitoring system shall affix such written notice of 

approval or a legible facsimile upon the equipment in a manner such that it is clearly 

visible and legible. 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 theAPCO.

(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:
AVAQMD RULE 218 218-3

Stack Monitoring

(a) Monitors for Gaseous Air Contaminants

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 
218-4 AVAQMD RULE 218

Stack Monitoring

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. [Suggested by comment 

letter of 03/17/2005. Derived from SCAQMD 218(a)(5)]

(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 218 218-5

Stack Monitoring

(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 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.
218-6 AVAQMD RULE 218

Stack Monitoring

(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.

(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.
AVAQMD RULE 218 218-7

Stack Monitoring

(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 ninetyfive 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.

(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.
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(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.

*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)]
AVAQMD RULE 218 218-9

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