Texas Commission on Environmental Quality Chapter 2.0 

Sampling Procedures Manual 

CHAPTER 2 

STACK SAMPLING FACILITIES 

General

Most sampling for representative results requires minimum sampling facilities for which the 

TCEQ has established the guidelines presented in this chapter. Stack sampling operations utilize 

a system of equipment to traverse a cross-section of the stack or duct through ports located such 

that a representative sample can be obtained. Normally, a monorail structure is erected so the 

cross-section of the stack may be traversed on two axes for circular stacks and on a matrix layout 

for rectangular or other shaped stacks. 

These guidelines cannot anticipate all situations, and special cases will occur. Non-standard or 

alternate installations are therefore evaluated on an individual basis, and in such instances 

detailed plans should be sent to the local TCEQ Regional Office sufficiently in advance for 

review and approval before the construction of stack sampling facilities is initiated. 

Various rules and regulations require that “safe and easy access” be provided for sampling. 

Facilities deemed insufficient by a TCEQ observer whether due to unsafe, crowded, or other 

conditions may preclude the observation of the sample and, in turn, the acceptance of the results. 

The following guidelines constitute minimum requirements for safe and accessible stack 

sampling facilities. No attempt has been made to incorporate official safety rules, but all such 

applicable regulations must be followed.

Physical Features

Before consideration is given to the installation of sampling ports and platforms, certain 

dimensions and other features of the stack and stack gas must be verified in order that a 

representative sample is possible. 

● Stack diameter must be at least four inches.

● Stack gas velocity head must be at least 0.05 inches of water. 

● The stack must have at least 2-1/2 diameters of uniform undisturbed cross-section. 

Sampling Ports

Port Location

The optimum location of sampling ports is at least eight stack diameters downstream of any 

bends, inlets, constrictions, abatement equipment, straightening vanes, or other flow disturbance; 

and at least two stack diameters upstream of the stack exit or other flow disturbance. Hydraulic 

diameter is used for non-circular stacks and is defined later in this chapter. This location permits 

a sample traverse to be taken using a minimum of twelve sampling points. A greater number of 

sampling points is necessary on stacks which fail to meet this location criteria. For a valid 

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Sampling Procedures Manual 

sample traverse to be obtained, however, sampling ports must be located at least two stack 

diameters downstream and at least one-half stack diameter upstream from any disturbance. If a 

2-1/2 diameter length of uniform undisturbed stack cross-section is not available, stack 

modification must be made or an alternate sampling location must be chosen which will satisfy 

this criteria. 

To minimize the increase in the number of sampling points required on stacks with undisturbed 

cross-section less than 10 but greater than 2-1/2 stack diameters in length, the sampling ports 

should be located such that the distance from the ports to the nearest upstream disturbance is four 

times the distance from the ports to the nearest downstream disturbance (see Figure 2-1 for 

minimum number of sampling points required). The 2-1/2 diameter criteria must be met; while 

the 4:1 distance ratio is a recommendation. 

Port Size

Ports are minimum three-inch ID standard industrial flanged pipe with six-inch bolt circle 

diameter and closed by a removable blind flange. Larger port sizes are necessary on large 

diameter, double-walled stacks which necessitate longer ports, and six-inch ports are necessary 

for proportional PM-10 sampling. These ports should also be standard industrial flanged pipe. 

Ports no smaller than four inches inside diameter must be provided on stacks greater than ten feet 

in diameter. 

Port Installation

Ports shall be installed flush with the interior stack wall and shall extend outward from the 

exterior stack wall no less than three inches nor more than eight inches unless additional length is 

required for gate valves. Gate valves should be installed only when extreme stack conditions 

and/or the presence of hazardous materials require such devices for the safety of personnel. 

Ports should be installed no less than five feet nor more than six feet above the floor of the 

platform and the clearance zone described later in this chapter must be maintained. 

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Sampling Procedures Manual 

Figure 2-1 

Minimum Number or Traverse Points 

Number and Location of Ports on Circular Stacks

A minimum of two ports shall be installed on diameters 90o

 apart if the stack diameter plus one 

port length (stack inside wall to end of port extension) is less than ten feet. Four ports shall be 

installed on diameters 90o

 apart if the stack diameter plus one port length is equal to or greater 

than ten feet. One traverse should be located in the plane of any bend or other disturbance that 

may have inertial effects on particles in the flow stream.

Number and Location of Ports on Non-Circular Stacks

The same upstream and downstream distance requirements discussed previously apply to noncircular stacks. The hydraulic diameter (four times the area divided by the perimeter) is used in 

place of the circular diameter. This becomes (2AB)/(A+B) for a rectangular stack, where A and 

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B are the cross-sectional dimensions of the stack. The streamwise location of the sampling ports 

is determined in the same manner as for circular stacks using the hydraulic diameter. The 

hydraulic diameter is used only for determining the location of sampling ports and the required 

number of sampling points. Hydraulic diameter is not used in data reduction. 

The cross-stream location of the sampling ports is dependent upon the total number of sampling 

points required. Figure 2-1 is used to determine the required minimum number of sampling 

points by reading the curve corresponding to the number of upstream hydraulic diameters (B) 

and downstream hydraulic diameters (A) and selecting the higher number. 

The stack cross-section of square or rectangular stacks is divided into a matrix (i, j) of equal area 

rectangles such that i = j or i = j + 1 and i + j is equal to or greater than the total number of 

sampling points required. The number of sampling ports required is either i or j located along 

one side of the stack such that the centerline of each port is colinear with the centroid of each 

row of sampling points. 

Stacks with cross-sections which are not circular or rectangular must be equipped with an 

adequate arrangement of sampling ports so that the stack cross-section may be divided into a 

sufficient number of area increments for a representative sample. If equal area increments are 

not possible, time weighting of the sample at the various sampling points may be necessary. 

Detailed plans of such installations should receive advance approval by the TCEQ. 

Monorail Support Structure

The installation of a permanent monorail support structure is recommended to reduce set-up time 

and to eliminate the load-bearing requirements for the sampling ports. Figure 2-2 shows a 

drawing of the monorail support structure including the relative position of the bracket to the 

sampling port. This bracket is intended to be compatible with several types of sampling 

equipment. The loading requirements for ports or the monorail support structure are shown 

below. 

Port or Monorail Support Loading

The port or monorail support installation shall be capable of supporting the following loads: 

● Vertical load of 200 pounds 

● Horizontal load of 200 pounds 

● Radial load of 1000 pounds (along stack diameter) 

Work Platform

A work platform shall be provided around the stack circumference between the sampling ports 

and extending at least three feet beyond each port. If four ports are required, the work platform 

shall extend around the entire circumference of the stack. The minimum platform width shall be 

at least three feet measured radially with stack diameter. The work platform must be capable of 

supporting at least 2000 pounds. 

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Safe and easy access to the work platform shall be provided via ladder, stairway, or other 

suitable means. Safe guardrails shall be provided around the platform. No open ladder well, 

stairwell, or other such opening shall be located within three feet of any sampling port. Ladder 

wells shall be covered at the platform and any opening to the platform shall be equipped with a 

safety bar or chain at the opening. 

A temporary work platform for sampling operations is acceptable if proper safety and 

accessibility is provided. All other requirements detailed in this chapter such as for monorails, 

ports, loading, clearance, and power must be met by the temporary facilities. 

Figure 2-2 Monorail Support 

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Clearance Zone

A three-dimensional obstruction-free clearance zone shall be provided around each sampling 

port. The zone shall extend one foot above the port, two feet below the port, and two feet to 

either side of the port. The zone shall extend outward from the exterior wall of the stack at least 

one stack diameter (or stack radius if four ports are provided), plus one port length (inside wall to 

end of port extension) plus three feet. Although this clearance zone is generally adequate for 

most sampling efforts, sampling contractors may have other clearance needs. A general 

clearance zone is illustrated in Figure 2-3. 

Power Supply

Power requirements may vary from site to site and the complexity and frequency of testing 

requirements. For complex test efforts the test firm and source owner/operator should verify 

adequate power is available. For normal test efforts electrical power outlets shall be provided as 

follows: 

Platform Power 

At least one 115-volt, 15-amp, single phase, 60 hertz alternating current circuit with a grounded 

two-receptacle weather-proof outlet. Receptacles shall accept standard three-prong grounded 

household-type plugs or suitable adapters shall be provided. 

Stack Base Power 

Two 115-volt, 15-amp, single phase 60 hertz alternating current circuits with grounded tworeceptacle weather-proof outlets. Receptacles shall accept standard three-prong grounded 

household-type plugs or suitable adapters shall be provided. 

Vehicle Access and Parking

Vehicle access and parking space should be provided near the base of the stack for various 

communications and equipment transport lines to be strung to the stack platform. 

Gaseous Sampling - Concentration Only

Standard sampling ports and platforms are normally necessary for gaseous sampling because a 

velocity traverse is needed for flow rate determination in most cases. In sampling situations for 

which only pollutant concentration is needed or for which an accurate flow rate is available by 

other approved means, less elaborate sampling facilities may be acceptable. All facilities must, 

however, meet strength and safety requirements. 

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Sampling Procedures Manual 

Figure 2-3 Stack Facilities 

Gaseous sampling facilities for concentration only shall be sufficient for collection of a sample 

of stack gas according to standard gaseous sampling procedures. Adequate minimum facilities 

such as a one inch nipple shall be installed in the stack at a location where sufficient turbulence 

exists (no stratification) to insure a representative sample. Proper clearance must be provided for 

sampling operations or a permanent probe and sample line can be installed at the port location 

and extended to a more accessible sampling location. The probe and sample line must be 

installed so that leak checks can be made. 

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Sampling Procedures Manual 

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Permanent Monorail Systems

Source operators are encouraged to install permanent monorail systems on large stacks. 

Monorails must extend the full radial length of the clearance zone described previously, and 

must be capable of supporting a 200 pound load anywhere along the monorail track. Rollers 

must be properly lubricated and maintained in working condition. The sample box attachment 

hooks should be six inches above the port centerline. If the monorail is installed with the hooks 

more than six inches above the port centerline, suitable adapters must be provided. 

Miscellaneous Requirements

In addition to the specific requirements detailed in this chapter, other miscellaneous requirements 

are as follows: 

● Power hoists shall be provided for sampling platforms 200 feet or more above ground 

level. 

 ● Non-circular horizontal ducts should have provisions for vertical sampling. Circular 

horizontal ducts should have one vertical and one horizontal port. Suitable work 

platforms are necessary in both cases. 

● Heat insulation shall be installed as necessary on high temperature stacks for safety in 

the vicinity of the work platform. 

 ● The source operator is responsible for maintaining all sampling facilities in safe, 

useable condition at all times. 

● As mentioned earlier, one traverse should be located in the plane of any bend or other 

disturbance that may have inertial effects on particles in the flow stream. 

● Stacks may taper by as much as 15 degrees without the taper being considered a 

disturbance.

Excess Air

Additional facilities may be necessary for determining the composition and flow rates of feed 

stock and fuel on certain processes such as incinerators. This information, obtained at the time 

of sampling, is necessary to calculate the amount of air in the stack effluent in excess of 

stoichiometric. 

Cyclonic Flow

Cyclonic or swirling flow may be encountered in a stack or duct due to certain circumstances 

such as cyclone collectors or tangential duct entry. Corrective measures such as straightening 

vanes may be necessary to alleviate the cyclonic condition. 

The existence of cyclonic flow may be determined as described in Chapter 5. A method for 

sampling cyclonic flow is described in Appendix H, but advance approval should be obtained 

concerning its applicability for determining compliance status. 
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CHAPTER 14

CONTENTS OF AIR EMISSION TEST REPORTS 

General

This chapter provides guidance for submitting air emission test reports. Special sampling 

situations may arise that do not fit these categories; however, this chapter has been broadly 

designed to serve as a guide to the standardization and quality assurance practices that are 

generally necessary for a report to be considered complete. The four most common 

deficiencies of test reports are: insufficient documentation of process conditions, insufficient 

documentation of test activities, inadequate calibration of test equipment, and the lack of 

approval for alternate methods or method deviations. All testing activities should incorporate 

good laboratory practices. The procedures used for testing and reporting of results should be 

those which are commonly accepted in the field of air pollution control per 30 Texas 

Administrative Code (TAC) Section (§) 101.14. Incomplete reports may be considered as 

noncompliance, and could result in enforcement action against the owner or operator of the 

facilities. Texas Water Code, § 7.179, addresses intentionally or knowingly omitting material 

information, making false statements, concealing, and or altering any notice, report or other 

document required by chapter, rule or permit. 

Report reviews are conducted by the Texas Commission of Environmental Quality (TCEQ) to 

determine acceptability of the report based on the following general criteria: 

a. Is the air emissions test report in an acceptable and logical format? 

b. Is the air emissions test report complete? 

c. Have the Source’s applicable test requirements been fulfilled? 

d. How valid is the testing event’s raw test data? 

e. Were correct equations and terms used in the report’s calculations? 

A TCEQ conducted report review is the basis upon which an air emissions test Report is officially 

accepted or rejected by the Agency (TCEQ). The acceptability of a report is easier to determine 

if contents are complete and presented in a logical, organized manner, as illustrated in this 

chapter. Use of the TCEQ or Environmental Protection Agency (EPA) format for presentation of 

field data and calibration is encouraged to expedite report evaluation. Where possible, reports 

should conform to Texas Accessibility Standards. Guidance may be located at 

http://governor.state.tx.us/disabilities/accessibledocs or by contacting any TCEQ office for 

additional information. 
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The regulated entity should submit at least three copies of the report to the appropriate TCEQ 

regional office. Air permit Special Conditions may specify additional distribution of the report. 

One copy should be a bound hard copy. The other two may also be a bound hard copy, or 

contained in an electronic format. For electronic formats, the TCEQ can only accept a read-only 

compact disc (CD) and should be submitted in a slim jewel case. The currently acceptable file 

types for the CDs are: 

 .pdf (document format/image - Adobe) 

 .tiff (photographic/image) 

 .xml (extensible markup language – can be used to describe documents) 

 .doc (Microsoft Word) 

 .xls (Microsoft Excel) 

 .ppt (Microsoft PowerPoint) 

The regional office will forward a bound hard copy or CD copy to Central Records in Austin. The 

copy being sent to the Central File Room will be considered the official agency record. It is 

recommended that the following list be used as a checklist for the report to insure it is 

complete. 

Stack Sampling

Organization and submission of stack test reports in the following manner will facilitate TCEQ 

review. 

1) Table of Contents: Or an equivalent means of locating sections of the report, including 

additional volumes or appendices which may be required. Each page of the report should 

be numbered. 

2) Introduction: Background information pertinent to the test and testing requirements (title 

page may be sufficient if it contains the information below). 

a) Name and physical location of source sampled and date(s) of sampling. 

b) Identification of the process and name and number of the unit sampled using TCEQ 

Regulated Entity Numbers (RN), TCEQ Account Numbers, TCEQ Permit Numbers, and 

Emission Point Numbers. 

c) List of applicable testing requirements with brief explanation: 

i) Specific citations of TCEQ Rule numbers; TCEQ Permit numbers or permit by rule 

requirements; 

ii) The specific subparts and emission limit, testing, and reporting requirement rules of 

EPA New Source Performance Standards (NSPS), National Emissions Standards for 
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Hazardous Air Pollutants (NESHAP) National Emissions Standards for Hazardous Air 

Pollutants for Source Categories, commonly called Maximum Achievable Control 

Technology (MACT) Standards; 

iii) Other (e.g., Notice of Violation resolution, increased production rates, etc.). 

d) List of pollutants sampled. 

e) State whether this is the initial test, quarterly, or otherwise. 

f) A detailed explanation of any tests which were not completed for any reason. 

3) Summary: The portion of the air emissions test report that states the final results of the 

testing event and compares the results to the requirements, provisions and allowances of 

the applicable governing rules and standards. 

a) In the Test Report summary, include all pollutant mass emission rates, concentrations, 

removal or destruction efficiencies, emission to operation standard (e.g. lb./MMBTU, 

lbs./hp hr, lbs./MMgal loaded) or other applicable standard being determined during the air 

emissions testing event. Compare each result with the applicable standard(s), including: 

NSPS, NESHAP, MACT, TCEQ general and/or special provisions/conditions of the source’s 

Permit, Permit Application Representations, Exemption Demonstration Requirements, et

cetera (etc.). Submit the reading, sum or averages of pertinent support data measured 

during the testing event, in time units which are appropriate for use in the determination of 

the mass emission rate(s) of the air pollutants required to be tested for (by the source’s 

operating permit or the applicable Federal Subpart). 

i) Particulate emission rates including and excluding the impinger catch portion of the 

sample. The impinger portion of the sample may be excluded only in certain cases. 

ii) Percent isokinetic for each isokinetic sample. 

iii) Schedule of intermittent periods during sampling and the normal schedule of such 

events (e.g., Soot blowing, CEMS blowback, process downtime, batch process, etc.). 

iv) Operating level of the process during each sample or sample run, the normal 

operating level (usual), design maximum and maximum achievable operating levels. 

v) Statement of operating condition of all abatement equipment during sampling 

including any cleaning cycles associated with the abatement equipment (e.g., 

absorber regeneration, baghouse bag cleaning cycles, ESP rapping, etc.). 

b) Where previous testing was conducted summarize differences in the results, testing and 

operating conditions. 

4) Procedures: Description of equipment and procedures used during sampling and analysis 

a) If equipment, procedures, and analysis methods were exactly those described in the 

applicable sections of the TCEQ Sampling Procedures Manual, the Federal Register, and 

the Test Plan, include a statement to that effect along with a list of specific methods, 

procedures, and test equipment; schematic of instrumental analyzer sampling system, 

including all pumps, valves, mass flow controls, sample conditioning systems, heated 

lines, manifolds and atmospheric vents as configured during the test; any Reference 
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Method deviation(s) approved by the TCEQ, including the date approved, and name & 

title of the TCEQ representative who approved the deviation(s). 

b) If any equipment, procedures, and analysis methods were consistent with, but not 

identical to TCEQ Sampling Procedures Manual, the Federal Register, and the Test Plan, 

provide additional information for those efforts including a detailed description of such 

methods, procedures, and equipment used; written approval for any deviations from 

standard procedures including: the name and description of all special apparatus and 

alternative testing methods used during test; copy of the method and publication 

references; written documentation of alternate test method approval. 

c) Written approval for any major modification to a Reference Method. Written approval 

for any method(s) which was used that is not published in an EPA document, along with 

a copy of the method(s) detailing minimum and maximum detection limits, 

interferences, etc. 

5) Process Data: The averages of all process or production parameters recorded, calculated or 

determined during the air emissions testing event, in time units which are appropriate for 

use in the determination of the mass emission rate(s) of the air pollutants required by the 

source’s permit, state rule or the applicable Federal Subpart. Include the source of all 

parameter information. 

a) All other information necessary to calculate emissions or determine process activity to 

determine compliance with the standards or limitations being evaluated and show the 

proper operation of the facility for the tests being conducted, regardless of whether it is 

specifically or directly identified in the permit, state rule or the applicable Federal 

Subpart. Note: this information should generally be discussed and agreed on during a 

pretest meeting or other documented communication. 

b) All measured pollutant emissions: both including and excluding the impinger catch 

portion of extracted samples. 

c) Detail(s) of the following process or production rates for the facility, or the production 

or process unit in which the emission source is in service: 

i) Logs of process parameters as may be necessary to document levels of operation. 

All printouts obtained from process, such as load etc., must be accompanied by a 

description which identifies the parameters and units used; 

ii) Designed Rate; 

iii) Permitted Rate (if applicable); 

iv) Maximum Rate (if different from the designed rate); 

v) Production Rate(s) Demonstrated during the testing event(s); 

vi) Production Rates(s) Demonstrated during the Immediately Previous air emissions 

testing event, if applicable (recommended). 

6) Calibrations: Dated calibration records with dates and worksheets for all equipment used 

during sampling. The name and description of all primary air emissions testing equipment 

used during the air emissions testing event, including manufacturer, model number and 
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serial numbers. If in question, the adequacy of the calibrations will be compared to the 

procedures in the current edition of the Quality Assurance Handbook for Air Pollution 

Measurement Systems.

7) Lab data: Include laboratory analysis worksheets and results including tare weights, blank 

results, spiked samples, audit samples and recovery studies required by the test method. 

Additional information sufficient for an independent evaluation of the procedure may be 

required for complex methods such as daily calibrations, date and time analysis were 

conducted, audit materials, and laboratory certifications and accreditations or exemption 

from accreditation. Note: all analytical data generated by a mobile or stationary laboratory 

in support of compliance with air permits must be obtained from a National Environmental 

Laboratory Accreditation Conference (NELAC) accredited laboratory under the Texas 

Laboratory Accreditation Program or meet one of several exemptions. Specific information 

concerning which laboratories must be accredited and which are exempt may be found in 

30 TAC § 25.4 and § 25.6. For additional information regarding the laboratory accreditation 

program and a list of accredited laboratories and their fields of accreditation, please see the 

following Web site: 

www.tceq.texas.gov/compliance/compliance_support/qa/env_lab_accreditation.html

For questions regarding the accreditation program, you may contact the Texas Laboratory 

Accreditation Program at (512) 239-3754 or by e-mail at labprgms@tceq.texas.gov. Also 

include: 

a) A record of the chain of custody of the samples from sampling collecting through the 

final sample analysis. 

b) Visible emission determination, opacity data sheets, observer certification, etc., if 

conducted. 

8) Calculations: Example calculations of all applicable stack gas parameters, emission rates, 

and analytical results for the test which minimally include: 

a) Emission rates; 

b) Allowable emission rates (TCEQ, EPA); 

c) Excess air in stack; 

d) Cyclonic flow; 

e) Percent isokinetic; 

f) F factor; 

g) Soot blowing; 

h) Stack gas parameters (velocity, moisture content, ACFM, SCFM); 

i) Intermediate steps during analysis (titrations, aliquots, blanks); 

j) Assumptions and constants used; 

k) An example calculation using actual data from one of the valid test runs. 

9) Testing Personnel information: 
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a) Name and affiliations of all (including plant personnel) present during testing and their 

responsibilities during the test; 

b) Name, address, and telephone number of testing organization, laboratories used and 

consultants overseeing or responsible for the testing report or results with an 

appropriate contact name for acquiring additional information. 

10) Appendices: The portions of the air emissions test report that include various categories of 

supplementary and support information which is included to enhance the validity of the 

practices and procedures conducted prior, during and subsequent to the air emissions 

testing event. 

a) Schematic drawing of stack (elevation and plan views) showing all dimensions, sampling 

port locations, inlets, outlets, and nearest upstream and downstream flow disturbances 

with sampling point locations shown on plan view. Pictures of emission points may be 

substituted for drawings; however, measurements of the interior dimensions of the 

emission point are required. 

b) Copies of all raw data taken during sampling. Record all handwritten data exclusively in 

indelible ink by all test and plant personnel, during the air emissions testing event. 

Include all data generated during the test by any instrumentation such as strip charts, 

integrator printouts, data acquisition system printouts; ensure that it is completely 

reproduced legibly. Clearly indicate the duration of all test runs, calibrations, and other 

significant events. 

c) Also required as part of the report submittal is pretest meeting documentation, if a 

pretest meeting was held. 

d) A copy of the TCEQ permit, if any, which applied to the unit(s) at the time of the testing 

to document the language and emission limits at the time of the testing. For testing 

required under the provisions of TCEQ flexible permits, include a calculation of 

emissions to compare to the cap on the day of testing for all emissions sources under 

the cap. Use the Hourly Cap Compliance Demonstration Summary Table (HCCDST) to 

report the data. 
Texas Commission on Environmental Quality Appendix P

Sampling Procedures Manual

Revision No.: One P-1 1/2003

APPENDIX P

COOLING TOWER MONITORING

General

Cooling tower monitoring describes the characterization of volatile organic air pollutants that are

capable of being air-stripped from a water matrix. While generic or indicator monitoring may be

required to identify the existence of volatile organic compound (VOC) emissions, speciated

compound characterizations may also be required in some instances to characterize the specific

compounds present.

Historically, a method for cooling tower water characterization was developed for use by El Paso

Products Company in the early 70's. This method utilized a dynamic or flow-through system for air

stripping a sample of the water and analyzing the resultant off-gases for VOCs using a common

flame ionization detector (FID) analyzer, and has been the popular choice in Texas for many years.

The El Paso Products method, however, has been overshadowed nationally by the use of purge and

trap analysis of water samples utilizing gas chromatography and/or mass spectrometry techniques.

While direct water analysis has been shown to be effective for cooling tower measurements of

heavier molecular weight organic compounds with relatively high boiling points, Texas Commission

on Environmental Quality (TCEQ) has determined that this approach may be ineffective for capture

and measurement of volatile organic compounds with lower boiling points, such as ethylene,

propylene, 1,3-butadiene, and butenes. VOCs with a low molecular weight and boiling point are

generally lost in the sample collection step of purge/trap type analyses. Consequently, TCEQ

requires that the air stripping method presented in this manual be used for cooling tower and other

applicable water matrix emission measurements of VOCs with boiling points below 140 o

F. Specific

procedures for cooling tower sampling and analysis for VOCs with boiling points of 140 oF and

greater must be submitted to TCEQ for approval on a case-by-case basis.
Texas Commission on Environmental Quality Appendix P

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Revision No.: One P-2 1/2003

Air Stripping Method (Modified El Paso Method) for 

Determination of Volatile Organic Compound Emissions from Water Sources

1.0 Principle and Applicability

1.1 Principle. A continuous stream of cooling water, process water, or wastewater is

supplied via a hard pipe or direct interface to an air stripping column apparatus for analysis.

Air flowing countercurrent to the water strips volatile organic compounds from the water for

analysis. Some gases may flash from the water immediately upon entering the apparatus and

these gases are trapped and mixed with the air stripped compounds. The concentration of

the air stripped compounds combined with the flashed gases is determined at the apparatus

air outlet by a suitable detector and/or by sampling. Concentrations of air stripped

compounds in the air exhaust, along with the air and water flow rates, are used to determine

concentrations of strippable volatile compounds in the water. A FID analyzer is used to

determine a value of “combined” or “total” strippable volatile organic compounds. Samples

may also be collected in sample canisters for shipment to analytical laboratories for

speciation of air contaminants. A gas chromatograph (GC) with an appropriate detector may

be used to determine specific stripped species. 

1.2 Applicability. This method is applicable to cooling tower water systems and may be

applicable to qualitative and/or quantitative measurements on other sources such as API

separators and wastewater systems.

2.0 Sensitivity

2.1 The sensitivity of this method for the onsite analysis by FID analyzer is typically 0.1

to 0.5 part-per-million, by volume (ppmv) methane in the stripped air, depending on the

specific analyzer. The sensitivity of the GC speciation analysis will vary depending on the

detector used. Detection limits as low as 2 - 50 part-per-billion, by volume (ppbv) in the

stripped air may be possible with the use of a gas chromatograph equipped with a mass

spectrometer (GC/MS).

2.2 FID Response. Response factors are not used to correct the total VOC measurement by

FID analyzer. Speciation analysis of the VOCs present in the stripped gas would be required

to correctly apply any proportioned response factor to the total VOC measurement, in which

case, the results should be calculated from the speciated analysis rather than the total VOC

results. Some chemicals, such as formaldehyde, will not respond well on a FID, having

particularly high response factors and, therefore, high detection limits. The total VOC
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Sampling Procedures Manual

Revision No.: One P-3 1/2003

procedure by FID should not be used on sources for which any potential targeted VOC has

a response factor multiplier greater than 2 relative to methane. Such sources must either be

sampled following the speciation procedure in Section 6.2, or an alternative detector,

approved by the TCEQ, must be used in the total VOC procedure in Section 6.1. Alternative

sampling and analysis procedures such as sorbent tube sample collection and analysis by

high performance liquid chromatography (HPLC) are subject to TCEQ approval.

3.0 Equipment and Materials

3.1 Air stripping apparatus. An air stripping apparatus as presented in Figure 1 and meeting

the following requirements: 

3.1.1 The stripping chamber shall be a cylinder 36 inches in length with an internal

diameter of 3 inches, and constructed of clear, heavy-walled glass.

3.1.2 The stripping chamber packing material shall be beryl saddles between 6 to 8

millimeter size. The depth of the packing material will be 26 inches.

3.1.3 The end caps of the stripping chamber must meet the dimensions specified in

Figure 2. Neoprene stoppers are recommended; however, securing clamps will be

required to prevent leakage. Black rubber stoppers are not allowed due to the

potential absorption and release of organic compounds. Alternative designs for the

end caps, such as customized threaded plastic caps with Neoprene gaskets, are

acceptable provided the materials used are non-reactive with the sample matrix or

target compounds, and the end caps meet the specifications in Figure 2. The tip of

the water sample inlet line is intentionally left 5 to 6 inches above the water level in

the stripping chamber to help accelerate the response of the system as some VOCs

will be released immediately as the water falls into the chamber. 

3.1.4 Tubing used in the air stripping apparatus for transporting gas and water shall

be 1/4 inch stainless steel or Teflon material. Stainless steel or Teflon 1/4 inch

tubing of minimal length shall be used to route water sample from the sample tap to

the air stripping apparatus. The water sample tubing from the sample tap shall not

be more than 50 feet in length. 

3.1.5 Drying agents, such as DrieriteTM, for removing moisture from the stripped air

stream before analysis by FID or collection in sample canisters are strictly prohibited

to prevent loss of VOCs to the drying agents. An empty, clear-glass flask is used as

a knock-out to remove some of the moisture in the stripped air stream, but gas

exiting the stripping chamber will essentially be at saturated moisture for the ambient

conditions. Different styles of knockout flasks are acceptable; however, the flask

must be clear-glass and 500 ml or less in size. Some FID analyzers may not be able

to monitor for prolonged periods under such conditions and intermittent monitoring

may be required.

3.1.6 A T-union with one leg leading to a bubbler must be included as shown in

Figure 1. Excess air not drawn into the analyzer probe or sample canister is vented
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through the bubbler and serves to indicate that sufficient flow has been established.

This is to assure that the sample is only from the stripped air and is not drawing in

any external air. With the bubbler in place, care must be taken not to pull water into

the FID analyzer or sample canister.

3.1.7 Gas bubble formation in the water rotameter can sometimes result from the

pressure drop across the water rotameter control valve. Significant gas bubbles can

interfere with accurate measurement of the sample water flow to the stripping

chamber. A suggested possible solution to this problem is to place a control valve

downstream of the water rotameter. By opening the rotameter to the fully open

position or using a non-metering rotameter, and controlling the flow with the valve

after the rotameter, the pressure drop occurs after the rotameter and bubble formation

may be minimized. This approach may require a fine-adjusting control valve to

achieve the flow rate control desired, and the tester must be certain that the water

rotameter can withstand the pressure in the water source being sampled.

Note: The TCEQ air stripping apparatus design is based on the apparatus designed

by El Paso Products Company of Odessa, Texas (see Reference 9.1) 

3.2 Flame Ionization Detector (FID) Analyzer. Analyzers with analog type readouts and

those normally used for leak detection are generally not appropriate for this method because

such instruments are designed for much higher concentration measurement than would be

expected in the air stripping apparatus effluent. FID analyzers used in conjunction with the

method must:

3.2.1 be a digital readout type, readable to 0.1 ppmv.

3.2.2 be able to meet the calibration requirements specified in Section 4.1.

3.2.3 have a sampling rate less than 2000 ml/min since the stripping air flow rate is

2500 ml/min and an excess air flow is required.

3.3 Gases for Air Stripping Apparatus Operation and FID Analyzer Calibration.

3.3.1 Zero Calibration Gas and Stripping Air. Air, certified to contain less than or

equal to 0.1 ppmv of total hydrocarbon (THC).

3.3.2 High-Level Calibration Gas. Cylinder gas standard of methane in air, certified

by the manufacturer to be within ±2% of the specified concentration. If the sample

concentration of VOCs in the stripped gas is less than 10 ppmv as methane, the span

gas calibration standard shall be 10 ppmv methane. Higher concentration span

calibration standards may be necessary for some sources. If a higher calibration

standard is required, select a high-level concentration such that the measured sample

concentrations are between 10% and 100% of the high-level calibration gas

concentration.

3.3.3 Mid-Level Calibration Gas. Cylinder gas standard of methane in air, certified

by the manufacturer to be within ±2% of the specified concentration. The mid-level

calibration gas concentration shall be between 20% and 50% of the high-level
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calibration gas concentration. (See note under 4.1.2.4.)

3.3.4 Certified gases must be used within the manufacturer’s specified shelf life, or

recertified upon expiration.

3.3.5 Subject to TCEQ approval, calibration gas standards other than methane may

be used for sources that have only one or a predominate potential VOC present in the

water matrix.

3.4 A gas chromatograph equipped with appropriate detector(s) for laboratory or field

speciation of the specific organic components.

3.5 Sample canisters. Internally passivated stainless steel canisters for collection of air

stripped samples for speciation analysis by GC. Sample canisters shall meet all requirements

of Compendium Method TO-14A (US EPA Compendium for Determination of Toxic

Organic Compounds in Ambient Air, EPA Document Number 625/R96/010B). Each sample

canister shall be equipped with a) a vacuum gauge and b) either a needle valve for manually

regulating flow rate or an automated flow regulator (i.e., a critical orifice or mass flow

controller). 

3.5.1 TedlarTM bags may be used in place of stainless steel sample canisters, if the

following provisions are met:

3.5.1.1 Bag samples must be analyzed according to Title 40 Code of Federal

Regulations, Part 60, Appendix A, Method 18.

3.5.1.2 The recovery study for bag sampling in Section 8.4.2 of Method 18

must be performed for all the target compounds. The recovery study is

performed by metering a known volume of zero air through a water blank

stripping apparatus into the TedlarTM bag and then spiking the bag with the

target compounds. This step checks not only the potential loss of compounds

due to the permeability of the TedlarTM, but also loss due to condensed

moisture in the bag. Percent recovery for each target compound must be

between 70 - 130%, or TedlarTM bags are not acceptable for sample

collection. When TedlarTM bags are acceptable, as specified in Method 18,

analysis results for target compounds must be corrected for the percent

recoveries.

3.5.1.3 TedlarTM bags must be new and unused. 

3.5.1.4 TedlarTM bags shall be checked for leaks and contamination as

described in Method 18, Section 16.1.3.2. 

3.5.1.5 Samples in TedlarTM bags must be analyzed within 72 hours of

collection. Recovery study bags must be stored for the same period of time

as the sample bags.

4.0 Calibration.

4.1 FID Analyzer Calibration. 
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4.1.1 Initial/Periodic Instrument Performance Evaluation. Perform the calibration

precision and response time tests as described in Sections 8.1.2 and 8.1.3 of Method

21 in 40 CFR 60, Appendix A. 

4.1.2 Calibration Procedure. 

4.1.2.1 Warmup period. Follow manufacturer’s recommendations.

4.1.2.2 Zero calibration. Introduce the zero gas (or stripping air) to the FID

analyzer. Calibrate the analyzer to read 0.0 ± 0.2 ppmv. 

4.1.2.3 High-level calibration. Introduce the high-level calibration gas (10

ppmv methane) to the FID analyzer. Calibrate the analyzer to read within ±

5.0% of the calibration gas certified value. 

4.1.2.4 Mid-level calibration check. Introduce the mid-level calibration to

the FID analyzer. The FID analyzer response on the mid-level calibration

gas must agree within ± 5.0% of the calibration gas certified value. Note:

The mid-level calibration step is optional if the VOC emissions

determination is based solely on the results of the GC speciation analysis of

the sample canister or TedlarTM bag samples.

4.2 GC Calibration. 

4.2.1 GC analysis by Method 18.

4.2.1.1 Follow the calibrations procedures described in Sections 8.2.1.5.2.1

and 10.0 in Method 18.

4.2.1.2 Alternative procedure. If a facility or laboratory is performing the

same analysis on samples collected by this method on a daily basis, then the

calibration and standardization procedures in Section 10.0 of 40 CFR 60,

Appendix B, Performance Specification (PS) 9, may be used. The initial and

periodic calibrations must satisfy all the requirements of Method 18 Sections

8.2.1.5.2.1 and 10.0, as well as those in Section 10.0 of PS9. 

4.2.2 GC analysis by Compendium Method TO-14A (US EPA Compendium for

Determination of Toxic Organic Compounds in Ambient Air, EPA Document

Number 625/R96/010B)

4.2.2.1 Follow the appropriate calibration procedures described in Section 10

of TO-14A for the selected detector(s) in the GC system.

4.3 Air rotameter calibration. 

4.3.1 Calibrate the air supply rotameter system with a dry gas meter, soap film

flowmeter, or similar direct volume measuring device with an accuracy of ± 2

percent. 

4.3.2 Operate the rotameter at 2500 cc/min for at least three calibration runs for 10

minutes each. When three consecutive calibration flow rates agree within ± 5

percent, average the three flow rates. 

4.3.3 If the average measured calibration flow rate agrees within ± 5% of the

rotameter reading, the rotameter is acceptable. If the difference between the
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rotameter reading and the measured calibration flow rate exceeds ± 5%, then remark

the rotameter to the calibrated flow rate.

4.3.4 Perform the rotameter calibration before the first field test and semiannually,

thereafter. 

4.4 Water rotameter calibration.

4.4.1 Calibrate the water rotameter with a Class A volumetric flask, graduated

cylinder, or similar container with a volume known to ± 2% accuracy and capable

of holding a volume at least 4 times the calibration flow rate (i.e., a 500 ml

volumetric flask to calibrate the rotameter at 125 ml/min.) 

4.4.2 Operate the water rotameter at 125 ml/min while filling the container. Record

the time required to fill the container and calculate the actual flow rate based on the

container volume and time required to fill the container. Repeat until three

consecutive flow rates agree within ± 5% of the mean. 

4.4.3 If the average measured calibration flow rate agrees within ± 5% of the

rotameter reading, the rotameter is acceptable. If the difference between the

rotameter reading and the calibration flow rate exceeds ± 5%, then remark the

rotameter to the calibrated flow rate.

4.4.4 Perform the rotameter calibration before the first field test and semiannually,

thereafter. 

4.4.5 Alternatively, a Class A volumetric flask or graduated cylinder may be used in

the field test to collect water at the stripping chamber water exit and recording the

time required to fill the container. If this approach is used, the water rotameter need

not be calibrated.

4.5 Temperature probe calibration.

4.5.1 Calibrate the stripping chamber temperature probe against an ASTM mercury

thermometer or equivalent. The calibration shall be performed at or near 0 o

C, 20 oC,

and 40 oC. 

4.5.2 If the absolute temperature (in degrees Kelvin) measured by the temperature

probe agree within ± 1.5% at each reference point, the temperature probe is

acceptable. 

4.5.3 Perform the temperature probe calibration before the first field test and

semiannually, thereafter. 

5.0 Pretest Preparations

5.1 Selection of the sampling site.

5.1.1 Sample sites for cooling towers must meet the following criteria:

5.1.1.1 The sample port in the cooling tower return line header must be in a

location where the feed rates to the cooling tower water are still under
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pressure and prior to the release of the pressure to atmospheric or any vents

in the return line header. For example, if the cooling tower has an open

trough along the top of the tower which distributes water to each of the cells,

the water supply for the test should be taken prior to the cooling water

entering the distributing trough. 

5.1.1.2 The sample port/probe should not extend beyond the plane of the

pipe wall into water matrix.

5.1.1.3 Samples should be drawn from either the vertical section near the

base of the riser pipe (from the inside of the elbow to the riser) or the top of

a horizontal section prior to the riser pipe at a location where the pipe will be

completely full. 

5.1.1.4 For cooling towers with multiple risers, samples must be drawn from

a location prior to the risers unless sample ports are installed on each riser

and the distribution of water flow to each riser can be determined.

5.1.2 Sample sites for sources other than cooling towers were not considered during

the development of this method and selection criteria for such sources may be subject

to TCEQ approval. 

5.2 Sample canister preparation. These procedures are typically performed by the

laboratory conducting the speciation analysis.

5.2.1 Before each use, sample canisters shall be cleaned, certified, and prepared

according the procedures described in Section 11.1 of TO-14A.

5.2.2 Evacuate canisters to less than 0.05 mm Hg pressure at least 24 hours prior to

sample collection. Record the canister ID, vacuum, date, and time on a label

attached to the sample canister.

5.3 Setup of Apparatus.

5.3.1 Assure the unit is vertically level using a bubble indicator or some other level

indicator. If the stripping chamber is not level, channeling of the water or air flow

may occur in the chamber and result in inefficient stripping.

5.3.2 Connect the zero air supply to the air inlet of the air stripping apparatus.

5.4 Perform the calibration procedures for the FID analyzer as described in Section 4.1. 

5.4.1 If VOC emissions are to be determined only by sampling with sample canisters

and GC speciation, the mid-level calibration is optional since the FID analyzer is

only used for monitoring for system stabilization.

5.4.2 Record calibration results on a data sheet similar to that in Figure 3.

5.4.3 Some analyzers draw fuel air for the FID separately from the sample stream.

If the fuel air is drawn from ambient air without purification, variations in the

ambient level of THC may cause the instrument to drift. This can be especially

problematic if the analyzer is calibrated indoors and then taken out to process areas

for the test. Dramatic changes in ambient temperature may also cause instrument
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drift. Every effort should be made to calibrate the instrument under the same

conditions it is to be used. When moving from source to source, a calibration check

shall be performed on the analyzer to determine if changes in the ambient conditions

(i.e., temperature or ambient THC) have caused instrument drift. Calibration drift

checks shall be documented on the field data sheets. If the analyzer is not within the

calibration specifications given in 4.1.2, the FID analyzer must be recalibrated. 

5.5 Blank/Background Determination: The blank checks are especially important for

stripping systems that are used on multiple sources and the possibility of cross contamination

exists.

5.5.1 Zero Air Check

5.5.1.1 A zero air check is mandatory before each test, regardless if the

system was previously used on a different source or not.

5.5.1.2 Open the zero air supply to the apparatus and adjust rotameter to read

2500 ml/min. 

5.5.1.3 Monitor the air effluent from the apparatus with the FID analyzer to

determine the baseline reading of the empty stripping chamber and apparatus.

Record the analyzer reading on the data sheet.

5.5.1.4 If the zero air check indicates a background $ 1.0 ppmv as methane

in the stripped gas, then the apparatus should be purged thoroughly to

remove the contamination until an acceptable background is measured (< 1.0

ppmv as methane).

5.5.2 Water Blank Check.

5.5.2.1 Water blank checks shall be performed by the following schedule:

5.5.2.1.1 A water blank check shall be performed on all stripping

apparatus systems, mobile and dedicated systems, before initial use

in the field and at least once per month thereafter.

5.5.2.1.2 For mobile systems used on multiple sources, a water blank

check between sources is optional (except as noted in 5.5.2.1.3), but

is strongly recommended. 

5.5.2.1.3 A water blank check is mandatory before beginning a test

if the previous test or source for which the stripping apparatus was

used indicated a total VOC reading (ppmv as methane in the stripped

air) 10 times greater than the applicable allowable emission rate or

action level on the current source. See Equation 7-3 in Section 7.4.

5.5.2.2 In order to ensure the entire sampling system is free of contamination,

the water blank check is performed through the sampling line and water

rotameter. Using either a pump or gravity, fill the stripping chamber with

clean distilled water through the sample line and water rotameter until the

packing is just submerged. Adjust the water flow rate to 125 ml/min.

5.5.2.3 Restart the air supply and adjust to 2500 ml/min. Monitor the air

effluent from the apparatus with the FID analyzer to determine the baseline
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reading of the apparatus while the system is flowing with clean water.

Record the analyzer reading on the data sheet.

5.5.2.4 If the water blank check indicates a background $ 1.0 ppmv as

methane in the stripped gas, then the apparatus should be cleaned and purged

thoroughly to remove the contamination until an acceptable background is

measured (< 1.0 ppmv as methane).

5.5.2.5 Drain the blank water from the stripping chamber before sampling.

5.5.3 Recommended cleaning procedure. If air and water blanks are not sufficient

to remove contamination from the system, the system should be disassembled and

the components cleaned thoroughly. 

5.5.3.1 The stripping chamber should be cleaned with hot soapy water,

followed by 5 rinses of tap water and 5 rinses of distilled water. The

chamber may be baked off at 150 oC for at least 1 hour, if an oven is

available large enough to hold the chamber. Otherwise, the chamber will

have to be air dried.

5.5.3.2 The beryl saddles, moisture knock-out flask, and Neoprene stoppers

should be cleaned with hot soapy water, followed by 5 rinses of tap water, 5

rinses of distilled water, then baked off in an oven at 150 oC for at least 1

hour.

5.5.3.3 TeflonTM and stainless steel tubing, unions, and valves that contact

water or stripped air sample should be cleaned with hot soapy water, rinsed

by flushing with 5 volumes of tap water and 5 volumes of distilled water,

then purged with zero air or nitrogen while baked at 150 oC in an oven for at

least 1 hour. Stainless tubing too long to fit inside an available oven without

bending should just be purged with zero air or nitrogen after cleaning.

5.5.3.4 The water rotameter should be cleaned according to the

manufacturer’s recommendations, followed by flushing with distilled water

and purging with zero air or nitrogen.

5.5.3.5 Some components, such as plastic caps for the knock-out flasks and

some valves, may be heat sensitive and may be damaged if baked at 150o

C.

Such components should be baked at a lower temperature for longer periods,

purged with zero air or nitrogen without heating, or simply air dried, as

appropriate.

6.0 Sampling. This method presents two sampling approaches; an on-site determination of total

VOC using a FID analyzer, and an off-site determination of speciated VOCs by sample collection

in sample canisters followed by laboratory gas chromatography. Permit or applicable rule

requirements may prohibit using the on-site FID analyzer approach without prior approval by the

TCEQ. If the tester wishes to use both the on-site total VOC results and the laboratory speciated

results for mass emission determinations, then all requirements of both approaches must be

followed, including the mid-level calibration for the FID analyzer.
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6.1 On-site determination of VOC emissions by FID analyzer.

6.1.1 Connect the water sample supply line to the sample port on the source (i.e.,

cooling tower return line header). Before connecting the water sample line to the air

stripping apparatus water inlet, allow the sample water to flush through the sample

line for at least 5 sample line volumes.

6.1.2 With the stripping air flowing at 2500 ml/min to the column, connect the

sample line to the water inlet of the air stripping apparatus and start the sample water

flow into the chamber. Sample water flow rates higher than 125 ml/min during the

filling stages are permissible; however, reduce the flow to 125 ml/min once the beryl

saddles are submerged. Adjust the water overflow as necessary to maintain the water

level just above the beryl saddle packing. The column drain valve should not be

used to control the water level, particularly if the overflow is used to obtain the

sample water flow rate as described in Section 4.4.5. Periodically check the water

rotameter during sampling for gas bubble formation and the bubbler to assure that

sufficient air flow is maintained. Record a notation in the data sheet comments

section if any gas bubbles are observed in the water rotameter.

6.1.3 After the water level in the stripping chamber has reached the appropriate level

and the air and sample water flow rates are set to 2500 ml/min and 125 ml/min,

respectively, allow the stripping apparatus system to stabilize for a minimum of 10

minutes before making sample measurements. Longer stabilization time may be

required depending on the organic compounds present and the particular water

matrix. Before starting the test run record the time required for stabilization,

barometric pressure, ambient temperature, and the process water flow rate (i.e.,

cooling tower water flow rate in gallons per minute).

6.1.4 At two minute intervals, record the FID analyzer measurement, water rotameter

flow rate, air rotameter flow rate, and stripping chamber temperature. Adjust the air

and water rotameter flows as necessary to maintain the target flows of 2500 ml/min

and 125 ml/min, respectively; however, actual measured flows must be recorded.

Monitor and record the data for a minimum of ten minutes. 

6.1.5 Average the data from Section 6.1.4 and follow the calculations described in

Section 7.0 to determine the air strippable concentration and, if applicable, the mass

emission rate of VOCs from the water matrix.

6.2 Off-site determination of VOC by GC analysis. Samples of the stripped compound(s)

may be taken from the exhaust of the air stripping apparatus and analyzed off-site by gas

chromatography for speciated VOC results. It is strongly recommended that multiple

samples be collected since a sample container may leak or be lost during shipment to the

laboratory. 

6.2.1 Connect the water sample supply line to the sample port on the source (i.e.,

cooling tower return line header). Before connecting the water sample line to the air

stripping apparatus water inlet, allow the sample water to flush through the sample
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line for at least 5 sample line volumes.

6.2.2 With the stripping air flowing at 2500 ml/min to the column, connect the

sample port of the water to be analyzed to the water inlet of the air stripping

apparatus and start the sample water flow into the chamber. Sample water flow rates

higher than 125 ml/min during the filling stages are permissible; however, reduce the

flow to 125 ml/min once the beryl saddles are submerged. Adjust the water overflow

as necessary to maintain the water level just above the beryl saddle packing. The

column drain valve should not be used to control the water level, particularly if the

overflow is used to obtain the sample water flow rate as described in Section 4.4.5.

 Periodically check the water rotameter during sampling for gas bubble formation

and the bubbler to assure that sufficient air flow is maintained. Record a notation in

the data sheet comments section if any gas bubbles are observed in the water

rotameter.

6.2.3 After the water level in the stripping chamber has reached the appropriate level

and the air and sample water flow rates are set to 2500 ml/min and 125 ml/min,

respectively, allow the stripping apparatus system to stabilize for a minimum of 10

minutes before making sample measurements. Longer stabilization time may be

required depending on the organic compounds present and the particular water

matrix. Record the time required for stabilization, barometric pressure, ambient

temperature, process water flow rate (i.e., cooling tower water flow rate in gallons

per minute), and the total VOC concentration measured by the FID analyzer.

6.2.4 Before collection of a canister sample, check and record the initial canister

vacuum. If the canister vacuum has changed by more than 50 mm Hg (2 in Hg) from

the initial evacuation, then the canister shall be considered as leaking and cannot be

used.

6.2.5 Connect the sample canister to the air outlet of the air stripping apparatus with

the stripping air flowing and the sample canister valve shut. Excess air flow will be

vented through the bubbler. 

6.2.6 Open the sample canister valve to begin sampling. During collection, monitor

and record the water rotameter flow rate, air rotameter flow rate, and stripping

chamber temperature at 2 minute intervals. Adjust the air and water rotameter flows

as necessary to maintain the target flows of 2500 ml/min and 125 ml/min,

respectively; however, actual measured flows must be recorded. When using an

automated flow controller to regulate the flow rate into the sample canister, such as

a critical orifice or mass flow controller, select a flow rate equivalent to 1/10th the

canister volume per minute or less. If the canister flow rate is controlled manually

(i.e., without a critical orifice or other flow controller), great care must be taken to

not sample at a rate over the stripping air flow rate. For manually controlled

sampling, adjust the needle valve such that the change in canister vacuum is between

75 to 125 mm Hg (3 to 5 in Hg) per minute. The canister must be only partially

filled to help prevent condensation in the canister. Fill the sample canister until the

vacuum gauge reads between 125 and 250 mm Hg subambient pressure (-5 and -10
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in Hg). 

6.2.7 Once sample collection is complete, record the final sample canister vacuum,

sample collection time, and sample ID on the data sheet. Connect the FID analyzer

to the stripping chamber air exhaust and record the final total VOC concentration.

6.2.8 Where the possibility of condensibles exists in a sample, the sample container

may be heated above the stripping chamber temperature to help assure a

representative sample analysis. Copies of field data sheets should be included with

the samples so the laboratory is aware of the conditions at which the samples were

collected.

6.2.9 Upon receipt of the sample(s) and prior to analysis, the laboratory must check

and record the vacuum of the canister(s) to determine if any leakage has occurred.

Dilution air (meeting the specifications of Section 3.1.1) should only be added to the

canister at the laboratory performing the analysis and after the canister vacuum has

been recorded.

6.2.10 If TedlarTM bags are acceptable (see Section 3.5.1) for the target compounds

then follow the procedures in Steps 6.2.1 through 6.2.9 with the following

exceptions:

6.2.10.1 References to canister vacuum/pressure are not applicable to

TedlarTM bags.

6.2.10.2 Flow rate into the sample bag may be controlled by placing a

rotameter downstream of the bubbler and controlling the flow rate of the

bypass. Maintain a bypass flow of approximately 1.5 to 2.0 liter/min to fill

the bag at approximately 0.5 to 1.0 liter/min.

6.2.10.3 TedlarTM bags must be at least 10 liter size.

6.2.10.4 TedlarTM bags shall be filled to approximately 80% capacity during

sampling. 

6.2.10.5 If sample dilution is required, dilution gas should not be added to the

bag. Instead, a known volume of gas may be extracted from the bag and

diluted with a known volume of zero air. 

6.2.11 The sample(s) obtained for speciation analysis shall be analyzed according

to the procedures in either EPA Method 18 (Title 40 Code of Federal Regulations

Part 60 Appendix A) or Compendium Method TO-14A (US EPA Compendium of

Methods for Determination of Toxic Organic Compounds in Ambient Air, EPA

Document Number 625/R96/010B).

6.2.11.1 The target list of compounds for the analyses shall be determined

by permit or regulatory requirements. In the absence of such requirements,

a target list shall be generated based on a presurvey sample and analysis by

GC/MS. Subject to TCEQ approval, process knowledge may also be used

to generate a target list for the analysis.

6.2.11.2 All unidentified compounds detected beyond the target compounds

shall be quantified based an appropriate surrogate, such as propane.

6.2.11.3 Calibration of the GC system for speciation analyses shall be
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C

M P bc

RT a

atm

inHg = × × ××

×+ ×

(. )

( )

0 03342

273

performed according to Section 4.2. 

6.2.12 Appropriate chain of custody documents should be completed and accompany

all canister and TedlarTM bag samples, even in cases where a single company

performs sampling and analysis.

6.2.13 Average the stripping chamber air and water flow rates and the stripping

chamber temperature. Follow the calculations described in Section 7.0 to determine

the air strippable concentration and, if applicable, the mass emission rate for each

compound in the water matrix.

7.0 Calculations.

7.1 Calculation of the concentration of air strippable compound(s) in the water matrix is by

the following equation:

Equation 7-1

Where:

a = Sample water flow rate, ml/min.

b = Stripping air flow rate, ml/min.

c = Concentration of compound in the stripped air, ppmv, from the FID analyzer or GC

results. The total VOC result from the FID analyzer may be corrected based on the

background check from either the zero air or water blank check, but only from the

pretest background check. Post-test background checks may include residual

contamination from the current test run. In no case shall the total VOC concentration

by the FID analyzer be corrected by more than 1.0 ppmv as methane.

C = Concentration of air strippable compound in the water matrix, part-per-million by

weight (ppmw).

M = Molecular weight of the compound, g/mol.

P = Pressure in the stripping chamber, in Hg (typically assumed to be same as

atmospheric pressure).

R = 82.054 ml-atm/mol-K.

T = Stripping chamber temperature, o

C.

The equation is a material balance and the value “C” represents the concentration in ppmw

of the compound in the water matrix that was stripped and does not represent the total

concentration of the compound in the water matrix prior to air stripping. The concentration

of stripped VOC in the air is on a volume basis, but the concentration of strippable VOC in

the water is on a weight basis in a liquid phase; so the concentration value will appear much
Texas Commission on Environmental Quality Appendix P

Sampling Procedures Manual

Revision No.: One P-15 1/2003

ECF hr

lb

gallon ppm

=×× × ×

60 8 337 1

1 000 000

min .

, ,

c

RT a

P b

E ppm

F lb

mol

atm

inHg

lb

gallon hr

' ( )

. (. )

', ,

. = min

×+ ×

×× ×

×

×

× ×

273

16 04 0 03342

1 000 000

8 337 60

higher for the air phase. 

7.2 Molecular weight. For total VOC based on the portable FID analyzer procedure in

Section 6.1, calculate total VOC concentration in the water and emission rate based on the

molecular weight of methane, unless an alternative reference calibration standard is

approved by the TCEQ. For speciated VOC results based on procedures in Section 6.2,

calculate individual compound concentrations and emission rates based on the respective

compound molecular weights.

7.3 Calculation of VOC mass emission rate(s) from the concentration of strippable VOCs

in the water and the water circulation rate:

 Equation 7-2

Where:

C = Concentration of air strippable compound in the water matrix, part-per-million by

weight (ppmw).

E = Mass emission rate of VOCs, lb/hr.

F = Water circulation rate of source, gallons/min.

7.4 Calculation of methane concentration in stripped air equivalent to a mass emission rate

or action level (see Section 5.5.2.1.3). Equations 7-1 and 7-2 above are combined as

follows:

Equation 7-3

Where:

E’ = Allowable mass emission rate of VOCs or action level, lb/hr.

c’ = Methane concentration in the stripped air equivalent to emission limit or action level,

ppmv.
Texas Commission on Environmental Quality Appendix P

Sampling Procedures Manual

Revision No.: One P-16 1/2003

 16.04 = Molecular weight of methane, lb/mol. If a different calibration gas is used for the

portable FID analyzer, such as ethylene, use the appropriate molecular weight.

8.0 Use of Portable GC for Field Speciation Analysis. A portable GC, calibrated for a specific suite

of compounds, may be used in place of a FID analyzer, in which case the calculations remain the

same and the final result is the concentrations of speciated air strippable compounds in the water

matrix.

8.1 Setup. Same as Section 5.1, except calibration procedures for field GC analysis will

follow Section 4.2.

8.2 Blank/Background Check. Same as Section 5.5.

8.2.1 Note: In some situations where very low detection for specific compounds is

required, it may be preferable to check for background using the field GC.

8.3 Sample Measurement. Same as Section 6.1 with the following exceptions:

8.3.1 The FID analyzer can be used during the stabilization period to monitor the air

stripping apparatus effluent. Alternatively, the GC can be used to monitor during the

stabilization period; however, such an approach may drastically increase the time

needed.

8.3.2 A test shall consist of three separate injection/analyses of the stripped gases.

9.0 References.

9.1 Vernon, W. D. et. al., “A Device for Measuring Volatile Organic Carbon Emissions

from Cooling Towers Water,” Journal of Air Pollution Control Association, December,

1981, pages 1280-1282. 

9.2 United States Environmental Protection Agency Method 18 “Measurement of Gaseous

Organic Compound Emissions by Gas Chromatography,” Code of Federal Regulations, Title

40, Part 60, Appendix A, as amended through October 17, 2000 (65 FR 61744).

9.3 United States Environmental Protection Agency Method 21 “Determination of Volatile

Organic Compound Leaks,” Code of Federal Regulations, Title 40, Part 60, Appendix A, as

amended through October 17, 2000 (65 FR 61744).

9.4 United States Environmental Protection Agency Compendium Method TO-14A

“Determination of Volatile Organic Compounds (VOCs) in Ambient Air Using Specially

Prepared Canisters with Subsequent Analysis by Gas Chromatography,” Compendium of
Texas Commission on Environmental Quality Appendix P

Sampling Procedures Manual

Revision No.: One P-17 1/2003

Methods for Determination of Toxic Organic Compounds in Ambient Air, EPA Document

Number 625/R96/010B, January 1999.
Texas Commission on Environmental Quality Appendix P

Sampling Procedures Manual

Revision No.: One P-18 1/2003

Air Stripping Apparatus for

Strippable VOCs from Water

To FID Analyzer/

Sample Canister

Bubbler

(250 ml flask)

Vent

Water

Overflow

Water

Level

Stripping Chamber 36" x 3"

Packed 26" Deep w/ Beryl

Saddles (6 - 8 mm size)

Air Rotameter

Water Rotameter

Temperature

Probe

Moisture

Knock-out

(250 ml flask)

Sample Water In

Stripping Air In

Column

Drain

Valve

Securing Clamp

Neoprene

Stopper

1/4" Stainless Steel

or Teflon Tubing

Excess

Stripped Air

Neoprene

Stopper

Water Flow Path

Air Flow Path

Figure 1
Texas Commission on Environmental Quality Appendix P

Sampling Procedures Manual

Revision No.: One P-19 1/2003

Air Stripping Apparatus

Stripping Chamber End Cap Design

Temperature

Probe

Water Inlet Line

(must be centered)

Stripped Gas

Exit Line

Stripping Chamber Top

Top View Side View

Stripped Gas

Exit Line

Water Inlet Line

(must be centered)

Stripping Chamber Bottom

Top View Side View 3 - 4 inches

0.5 inch

0.5 inch 0.25 inch

Stripping Air Inlet Line

(must be centered)

Water Drain Line

Water Drain Line

Stripping Air Inlet Line

(must be centered)

Figure 2
Texas Commission on Environmental Quality Appendix P

Sampling Procedures Manual

Revision No.: One P-20 1/2003

Figure 3

Air Strippable VOCs in Water

FID Analyzer Measurement Data Sheet

Regulated Entity: __________________________ Regulated Entity No: __________________________

Air Account No: __________________________ Instrument Model: __________________________

Unit Name: __________________________ Instrument Serial No: __________________________

EPN/FIN ID No: __________________________ Operator(s): __________________________

Process Description: _______________________ Certified Gas Value: Zero: ___________________

Date/Time: __________________________ Mid-level: ___________________

Barometric Pressure: ___________________ High-level: ___________________

Process Water Flow: ___________________ FID Response Zero: ___________________

Zero Air Background VOC: ______________ Mid-level: ___________________

Zero Water Background VOC: ______________ High-level: ___________________

Stabilization Time: ___________________ Expected VOC(s): __________________________

Time*

Air Stripping Apparatus Data FID

Reading

(ppmv, wet) Comments

Water Flow

(ml/min)

Air Flow

(ml/min)

Temp.

(

o

C)

Average

* Data recording time (after stabilization period), recorded as actual time of day. 
Texas Commission on Environmental Quality Appendix P

Sampling Procedures Manual

Revision No.: One P-21 1/2003

Figure 4

Air Strippable VOCs in Water

Canister Sampling Data Sheet

Regulated Entity: __________________________ Regulated Entity No: __________________________

Air Account No: __________________________ Instrument Model: __________________________

Unit Name: __________________________ Instrument Serial No: __________________________

EPN/FIN ID No: __________________________ Operator(s): __________________________

Process Description: _______________________ Certified Gas Value: Zero: ___________________

Date/Time: __________________________ High-level: ___________________

Canister ID: __________________________ FID Response Zero: ___________________

Sample ID: __________________________ High-level: ___________________

Barometric Pressure: ___________________ Zero Air Background VOC: ___________________

Ambient Temperature: ___________________ Zero Water Background VOC: ___________________

Stabilization Time: ___________________ Expected VOC(s): __________________________

Process Water Flow: ___________________

Time* Air Stripping Apparatus Data Canister

Flow Rate,

if applicable

(cc/min)

Canister

Vacuum

(mm Hg)

FID

Reading,

(ppmv, wet)

Comments

Water

(ml/min)

Air

(ml/min)

Temp.

(

o

C)

Average

* Data recording time (after stabilization period), recorded as actual time of day.