Most Frequently Asked Stack Test Questions

Technical Note

Most Frequently Asked Stack Test Questions


With the role of the Agency observer expanding, it becomes imperative that the observation of a compliance test be performed so legal and defensible data can be acquired inorder for proper regulatory compliance decisions to be made.  The primary activity of the Agency observer is to evaluate and document the representativeness of the applicable compliance test methodology.  The basic criteria for evaluation include:


  • Process and control equipment must be operating to produce representative emissions;
  • Representative sample of those emissions are acquired at the sample port and sampling points within the stack;
  • The sample train must collect and contain representative emissions of the analytes under consideration without affecting their concentration;
  • The sample recovery and analysis must be representative of the sample collected in the sample train; and
  • The reported results must be representative of the sample recovered and analyzed.


To assist with evaluation of stack test performance and documentation, a list of the most frequently asked questions, along with their answers, has been compiled as an instructional tool.  The questions relate to Federal Reference Methods 1-5 along with questions associated with SW-846 methodology.


  1. Where Can I Find A Copy of SW-846?


SW-846 may be purchased in hard copy from:  National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA, 22161, Ph: (703) 487-4650, Fax:  (703) 321-8547, E-mail:  Info@NTIS.FEDWORLD.GOV, Internet:

In addition, an electronic version can be reviewed and downloaded by visiting the Internet site at:




  1. Could You Please Explain the Difference Between Isokinetic and Anisokinetic Sampling?


During the course presentations, we viewed a video tape that explained the term “Isokinetic Sampling.”  Isokinetic sampling conditions exist when the velocity of the

particles and gases entering the probe nozzle tip (Vn) is exactly equal to the velocity of the stack gases (Vs), that Vn = Vs.  Percentage isokinetic is then calculated:


percent isokinetic (% I) = Vs/Vn X 100


When Vn does not equal Vs, we have anisokinetic conditions where sample concentrations can be biased because of the inertial effects of particles in the gas stream.  Depending on the particle composition and sizes in the gas stream depends upon how much effect there will be on the final pollutant mass rate (pmr) from the facility.   In general, the following conditions exist in a stack gas stream:

  • Small particles (< 1 micron) tend to follow the stream lines of the gas stream.  If the source is composed of only small particles, then really little effect on whether you sample above or below isokinetics, thus little effect on the pmr.
  • Large particles (> 5 microns) tend to move in their own initial direction.  For under isokinetic sampling (the nozzle is bring in gas at too low a rate), the gas stream “bunches up” at the nozzle inlet.  The large particles tend to “punches through” the “stream lines” (due to their own inertia) and into the nozzle area (they should have gone around the nozzle), thus biasing the pmr higher associated with a lower sample volume. We consequently have too many large particles for the small volume sampled.  For over isokinetic sampling (the nozzle inlet velocity is greater than the passing gas stream velocity),  the nozzle brings in gas not directly infront of it.  The large particles, due to their inertia, do not follow the stream lines and continue in the same direction.  Thus, the nozzle samples a non-representativeness of large particles in the gas stream, but for twice the volume of gas sampled through the nozzle (the larger particles enter the nozzle as if 100 % isokinetic sampling was occurring).  The small particles enter the nozzle outside the effective area of the nozzle (the small particles follow the bent stream lines into the nozzle).  Consequently, with the combination of the effects of the large and small particles, the pmr increases.
  • Intermediate particles are somewhat deflected for the stream lines of the gas stream.

How do we use this information in determining if you should reject or accept the stack test if the percent isokinetics are outside the 90-110 % limits and the source pmr were within their limits.  If the source test report shows that the percent isokinetics was under 90 % and majority of the particles were < 1 micron in size, then the test should be accepted since fine particles effect pmr very slightly.  In the same manner, if the particles are > 5 microns and the percent isokinetics are less than 90 %, then the test should be definitely accepted since the results are bias high anyway due to large particles (more large particles for a smaller sample volume).  Therefore, accept the results even so the isokinetics were below 90 %

Now, if the pmr is above the emission limit and we have < 90 % isokinetics, one can multiply the pmr by the factor %I/100 and recalculate pmr.  If this adjusted pmr is still higher than the standard, then the test is accepted even with the percent isokinetic over 110 (the results are in favor of the EPA).  On the other hand, if the adjusted pmr is lower than the standard (thus bringing them into compliance), then reject the test and require a retest to be performed.

If the pmr is above the emission limit and the % I is above 110 %, then the test should be accepted because the pmr is equal to the true value or bias low relative to it;  thus, the pmr is definitely over the standard.  If pmr is below the standard and the % I is above 110 %, then perform the same correction as above to the pmr (multiply by %I/100), and if is still below the emission limit, the test should be accepted.  The pmr meets the standard even though the maximum adjustment (biases due to large particles) have been made.  On the other hand, if the adjusted pmr exceeds the standard, you can accept the test results even though they did not meet the 90-110 % I because they still exceed the standard.


  1. Where Do I Go to Get References to Title III Hazardous Air Pollutants (HAPs), Their Boiling Points and Vapor Pressure?


During the presentation on Defining Hazardous Air Pollutants (HAPs), we discussed the methodology EPA uses to define the Clean Air Act Amendments of 1990, Title III, HAPs by boiling point (BP) and vapor pressure (vp).  EPA uses eight categories to define HAPs according to vapor pressure:

  • Very Volatile Organic Compounds [VVOC] (vp> 380 mm Hg)
  • Very Volatile Inorganic Compounds [VVINC] (vp> 380 mm Hg)
  • Volatile Organic Compounds [VOC] (vp 0.1 to 380 mm Hg)
  • Volatile Inorganics [VINC] (vp 0.1 to 380 mm Hg)
  • Semi-volatile Organics [SVOC] (vp 10-1 to 10-7 mm Hg)
  • Semi-volatile Inorganics [SVINC] (vp 10-1 to 10-7 mm Hg)
  • Non-volatile Organics [NVOC] (vp < 10-7 mm Hg)
  • Non-volatile Inorganics [NVINC] (vp < 10-7 mm Hg)

Using boiling points, the EPA defines HAPs by three broad categories:

  • Volatiles (VVOC/VVINC/VOC/VINC)    BP < 100 C
  • Semi-volatiles (SVOC/SVINC)                 BP  100 to 300 C
  • Particles (NVOC/NVINC)                        BP  > 300 C

As you recall, we use this information to help us pick the proper sampling train to capture our analytes.  Particles would use a filtration technique, semi-volatiles would use both filtration and adsorbent, and volatiles would a combination of adsorbents in the sample train.

You were provided a copy of the paper written by Larry Johnson and myself that included the listing of the CAAA of 1990 Title III HAPs and appropriate sampling methods from EPA’s SW-846 Compendium for each of the listed HAPs.

Based upon that presentation, I have had many inquiries as to the availability of documents that list the BP and vp for the Title III HAPs.  EPA has funded three documents which have as part of them BP and vp for the Title III HAPs.  They are:

  • Ambient Measurement Methods and Properties of the 189 Clean Air Act Hazardous Air Pollutants (HAPs), EPA-600/R-94/187, October 1994. (EPA Project Officer:  Bill McClenny, 919-541-3158).
  • Simultaneous Control of PM-10 and Hazardous Air Pollutants II:  Rationale For Selection of Hazardous Air Pollutants as Potential Particulate Matter, EPA-452/R-93/013, October 1992 (EPA Project Officer:  Gary Blais, 919-541-3223).
  • Screening Methods for the Development of Air Toxics Emission Factors, EPA-450/4-91-021, September 1991 (EPA Project Officer:  Bill Kuykendal, 919-541-5372).

To obtain copies of these documents, you can order from EPA’s National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA, 22161, (703-487-4650, email:  Info@NTIS.FEDWORLD.GOV, Internet:

In reality, I would call each of the EPA Project Officers and have them send you a copy.  Remember, you must be persistent in your demands for a copy!  Don’t take a brush-off or no for an answer!

In addition, you can go to the Internet and get chemical and physical properties (i.e., vapor pressures and boiling points) for many HAPs.  That site is:


  1. You Mentioned MACT Standards and EPA’s Timeline.  Can You Further Explain the MACT Bins?


In Lecture 2, Regulations, we discussed EPA’s progress associated with the implementation of the MACT standards, which contain sampling and analytical guidance on quantifying emissions covered by the standard.  In December, 1997, EPA submitted a report to Congress entitled:  Second Report to Congress on the Status of the Hazardous Air Pollutant Program under the Clean Air Act.  According to the report, EPA has fulfilled the 2- and 4-year groups (bins) for approximately 25 % of the 173 listed source categories in the Clean Air Act Amendments of 1990.  The Agency is, however, falling behind on promulgating standards for the 7- and 10-year groups.  Twenty-nine (29) new standards were to be originally due in 1997, but will now be promulgated in 1998.  With each of these standards, test methods must be identified for compliance purposes.

One of the interesting areas that is still under discussion is whether residual risk (10 -6) issues will apply once the MACT standard is in place for a source category.  As you recall in our presentation, we discussed the the requirements in the CAAA of 1990 that the after applying MACT, the Agency can return to the source category and apply additional controls for residual risk!  This issue has not been resolved to date and is one of the reasons the Agency is behind on meeting the MACT schedule identified in the CAAA of 1990.  Failure to meet the schedule would require the Agency to set case-by-case MACT standards, which might lead to more stringent application of control technology and emission limits.  The Agency would like to prevent a case-by-case MACT program, due to cost and manpower.

Consequently, the Agency has developed a MACT Partnership Program.  The program is designed to ease the burden of establishing MACT standards for all source categories and help the Agency meet its schedules for promulgating standards.  The program has two phases:  Phase I involves the Agency developing a presumptive MACT standard based on limited data it has gathered (without additional stack test).  During this phase, EPA and state/local agencies agree on the presumptive standard.  Phase II involves final-standard development, which then brings in stakeholders (industry, consultants, affected facilities etc.) for final rule development.  The two phase approach reduces the normal time of MACT standard development from 4 years to about 2 years.


  1. How Do We Use The Fo Factor in Determining Validity of Orsat/CEM Analysis for O2/CO2?


Fo factors can be used to evaluate the correctness of the Orsat or CEM system performing analysis for CO2/O2.  The following table illustrated the typical range for Fo factors for specific fuel types:

Using the following formula, one can check the accuracy of the Orsat or CEM used to monitor O2 and CO2:

Fo  =  20.9- O2/ %CO2

If calculated Fo value does not fall within this range of +/- 10 %, then something is wrong with the reported CO2 and O2 concentrations. 


  1. How Do You Take a Reading For Delta p and Delta h When The Meniscus Line Is Not Horizontal To The Manometer Tube?


When reading a meniscus, the analyst must be very careful that no error is introduced into the reading due to parallax.  Under normal conditions, the chemist reads the meniscus on a horizontal “line-of-sight” at the bottom of the crescent-shaped body from the concave wetting of the liquid on the walls of the container (convex if it does not, i.e. mercury in a glass tube).  Remember, the error associated with 0.1 in. water in reading the delta p was 2.4 % associated with the mass emission rate.  One can read the incline manometers on the Method 5 sample box to within 0.05 in. water.  Therefore, the error would only be very slight to the other possible errors in recording data and the operation of the sample train.  This is also true for reading the delta h.  When reading the delta h or delta p in the field, keep your “line-of-sight” horizontal and read the “bottom” of the crescent-shape of the meniscus.


  1. What Is The Difference Between Method 9 and SIP Series VE (Methods 203 A, B, and  C)?  What Is The Difference Between Federal Reference Method 29 and SW-846 Multi-metal Method?


In terms of regulations, EPA has developed a series of methods which address different programs.  As you recall, we discussed in our regulation lecture (broadcast Day 1) the sources of the different test methods:

  • 40CFR 60, App. B: 00 Series, Performance Specification Test
  • 40CFR 51, App. M:  200 Series, SIP Methods
  • 40CFR 60, App. A: 00 Series, Federal Reference Methods
  • 40CFR 61, App. B:  100 Series, NESHAP Methods
  • 40CFR 63, App. A:  300 Series, MACT Methods
  • 40CFR264/265: 0000 Series, SW-846 Hazardous Waste Incinerator Methods

Consequently, EPA has promulgated different test methods to address different regulatory standards.  Some of these methods are the same method, but identified differently depending upon the regulatory program.

Consequently, there is no difference between FRM 29 and SW-846, Method 0060 for multi-metal sampling and analysis from industrial and hazardous waste incinerators.  For more information associated with FRM 29, contact Mr. Bill Grimley, US EPA, EMC, MD-19, Research Triangle Park, NC, 27711, (919) 541-1065.

Methods 203A, B, and C are field test methods, as found in 40 CFR 51, Appendix M (Test Methods for State Implementation Plans), applying Federal Reference Method 9 (40 CFR 60, Appendix A) procedures for state agency inspectors and visible emissions observers to use in determining visible emission compliance with averaging times other than 6 minutes, time exception standards, and instantaneous emission standards.  The methods also address visible emission sources other than the traditional stack emission point including sources of fugitive emissions.  For more information concerning EPA Methods 203 A, B, and C, please contact Mr. Peter Weslin, US EPA, Emission Measurement Center, MD-19, Research Triangle Park, NC, (919) 541-5242.


  1. If A Velocity Profile Has Been Performed on Two Set of Ports, One Port Above The Other (Lower Port 1.5 Diameters Downstream, Upper Port 2 Diameters Upstream), Can The NESHAP Test Be Performed At the Lower Port?


Alternative test method approval or variation to a Federal Reference Method (FRM) has always been on a “case-by-case” bases.  At the discretion of the Administrator, the following allowable alternatives can be made:

  • Approve minor changes to the reference test methods;
  • Approve an equivalent method;
  • Approve an alternative method which has been demonstrated adequate for determining compliance at a specific source; and
  • Waive the requirements for performance testing.

The Administrator is a Regional EPA official or officials of other agencies, such as regional, state, and local personnel.

In general, for an alternative method to be accepted, it must:

  • Be applicable and properly executed;
  • Include a detailed, written description of option in test report; and
  • Provide supporting data and rationale to show validity of option in the specified application.

In considering an alternative to a Federal Reference Method, Agency criteria for evaluating minor modifications should determine that:

  • Effect (or changes to the methodology) will be insignificant on final emission data results;
  • Changes will accommodate a situation that is considered unique and would apply only to sample site for which it is allowed;
  • All allowable alternative procedures in reference method will provide emission results of equal or greater value than standard procedures (Bias Concept); and
  • Agency can use same bias concept technique when evaluating alternative methods.

With reference to the question, the source would have to provide the needed information to show that the two sampling ports are equivalent and that a negative bias does not exist at the lower port.  In essence, the source should complete the Alternative Method Approval Request, found at the back of your Student Workbook.  This form contains four major sections:  1.  Requesting Organization; 2. Specific Application of the Alternative Method; 3.  Description of the Alternative Method; and 4.Support Data.

As part of this request, the source would provide data (to support the selection of the lower port) showing that cyclonic flow does not exist at the lower port, both velocity profiles are representative of the source emissions and do not vary within 10 % of each other, and if a gas test method is being performed, the concentration profiles for O2 (or CO2) are within 10 % of each other as determined by a portable O2/CO2 continuous emission monitoring (CEM) system.

The source would provide this support data as Part 4 of the Alternative Method Approval Request.


  1. Has FTIR Been Used in Stack Testing?


FTIR has been used as both emission and process monitoring at primary/secondary aluminum facilities, secondary lead, asphalt roofing, Portland cement plants, wool fiberglass/mineral wool facilities and utilities.  FTIR use has been validated for the determination of over 37 hazardous air pollutants (HAPs) directly, with an additional 18 HAPs through sample concentration.  EPA presently maintains a spectra library on the Internet.      

FTIR is presently being used to quantitate emissions from a variety of sources.  Under 40 CFR Part 63, Appendix A, FTIR is being proposed (tentative: under consideration) for three methods.  They are:

  1. Method 318:  Formaldehyde, Phenol, and Methanol Determination by FTIR;
  2. Method 320:  Generic Extractive FTIR Method for Industrial Emissions; and
  3. Method 321:  FTIR For HCl From Portland Cement Kilns.

Method 318 test method using FTIR is industry specific for the mineral wool industry, while Method 321 is industry specific for the Portland cement industry.  Method 320 is a generic, self-validating FTIR test method that can be applied to any source category.  It has the option for using in screening, validation requirements (Method 301),  and self-validation requirements (spiking etc.).  Method 321 will be a compliance method using FTIR for HCl emissions from Portland cement plants as part of the MACT regulations.  The system uses a heated sample line and a filter maintained at 350 F to control ammonium chloride formation.  Method 318 will more than likely be promulgated in the fall of 1998,  while Methods 320 and 321 will be promulgated in the spring of 1999.

For additional information associated with the application of FTIR to monitoring industrial emissions, please contact Ms. Rima Dishakjian, U.S. Environmental Protection Agency, MD-77A, Research Triangle Park, NC, 17711, (919) 541-0443.

Finally, EPA has produced a video entitled:  FTIR for Emission Measurements.  Please contact Ms. Dishakjian for receiving a copy.


  1. What Are Some Of The Test Methods Available For Monitoring Sulfur Compounds?


Within 40 CFR 60, Appendix A, there are several Federal Reference Methods (FRMs) which are used to monitor both the oxides of sulfur and reduce sulfur compounds.  As you recall, Federal Reference Methods 6 and 8 deal with the oxides of sulfur.  Federal Reference Methods 15, 15A, 16, 16A, and 16B deal with the reduced states of sulfur and total reduced sulfur (TRS) compounds.

New techniques have developed over the last several years in monitoring reduce sulfur compounds.  Recently, field and laboratory test have demonstrated the applicability of specially-treated interior whole-air canisters as a sampling mechanism for reduce sulfur compounds.  In this application, a gas sample is extracted from the source through a heated sample probe directly into a heated specially-treated interior whole-air canister.  After extraction, the canister (still heated) is immediately taken to an on-site laboratory for analysis using gas chromatography coupled to a flame photometry detector or a mass spectrometer.  The National Council for Air and Stream Improvement (NCASI) has validated this method (using Method 301) for many organic HAPs, and some reduce sulfur compounds from Kraft recovery boilers.

Other techniques include extractive FTIR, portable gas filter correlation (GFC) systems, ion mobility, specific gas permeation cells and a variety of continuous emission monitoring systems (CEMs).  Other techniques for monitoring reduce sulfur compounds from industrial sources can be found in a variety of databases.

There are many different databases available for assisting the analyst in determining which sampling and analytical procedure to use for a particular analyte.  Most of the databases are multi-media, containing information involving both water, soil, hazardous waste and air.  Some of the more useful databases are:

  1. Lewis Publishing Company, Compilation of EPA’s Sampling and Analysis Methods Database. This database contains 650 method and analyte summaries.  Each summary includes method name and EPA number, analyte, CAS registry number, instrumentation, method detection limits, sampling and sample container requirements, and more.
  2. U.S. Environmental Protection Agency, EPA Environmental Monitoring Methods Index (EMMI) Database, National Technical Information Service (NTIS), 5285 Port Royal Road, Springfield, VA, 22161, (703) 487-4650, E-mail:  Info@NTIS.FEDWORLD.GOV, Internet: The EMMI database is an automated inventory of information on environmental significant analytes monitored by the EPA and methods for their analysis.  The EMMI System serves for enhancement and national distribution to Regional EPA laboratories and offices as the single authoritative source for cataloguing the Agency’s analytical methods.  The EMMI database includes information on more than 2,600 analytes from over 80 regulatory and nonregulatory lists and more than 900 analytical methods.
  3. U.S. Environmental Protection Agency, Air Methods Database, Office of Emergency and Remedial Response, Edison, NJ, (908) 321-6738.  The Air Methods Database is a PC-based software package which allows the user to access summarized standard methods for chemical sampling and analysis associated with air emissions.  These summaries are used by the user as tools for applicability of a method for an analyte, method detection limits, operating range, and interference’s of the method and the type of media and sampler used top collect the analyte.

In addition, NTIS publishes each year a pamphlet entitled:  Environmental Software and Datafiles which contain additional sources of current sampling and analytical methods and simulation models, software and datafiles containing test results and chemical properties, and statistical methods.


  1. Benzoic acid, at high concentrations, has appeared in my field blanks, trip blanks, and samples using SW-846, Method 0010.  Is benzoic acid real or a breakdown product of XAD-2 resin?


As you recall, XAD-2 is a cross-linked styrene-divinylbenzene organic polymer adsorbent.  When used for ambient and source testing, the native XAD-2 must be certified clean prior to field application.  This requires Soxhlet extraction with an organic solvent ( 10% diethyl ether in hexane or methylene chloride) to remove residual organics (i.e., benzene, toluene or the xylenes) from the surface of the polymer.  Consequently, when ready for field use, the XAD-2 should come with a “Certificate of Cleanliness” from the laboratory indicating that there are no residual organics (i.e, < 4 ug/g of individual organics) on the resin bed.  This is very important since the detection limits we are trying to reach are 1.0 ng/m3.  Consequently, the benzoic acid should not be a contaminant on freshly extracted XAD-2 resin.

The field and trip blanks should also help one determine what is the source of the  benzoic acid.  When charging and recovering the Method 0010 sample train, the field blank should be exposed to the same atmosphere as the sample cartridge.  This means opening up the field blank and setting it in the same area as where the Method 0010 sample train is being charged or recovered.  At the end of each activity, the field blank is capped and stored with the other samples.  If benzoic acid is in the atmosphere from fugitive emissions, it would effect both cartridges (sample and field blank) the same.  As you recall, the trip blank is never opened.  The trip blank is prepared just like a sample, but is never exposed to the atmosphere.

However, because of it’s chemical structure,  XAD-2 can degrade when exposed to heat, sunlight, and oxidants.  To minimize the influence of heat, Method 0010 requires that the  source gas entering the resin bed be maintained to < 68 F through the use of a coiled condenser during sampling to prevent deterioration of the XAD-2 resin.  In addition, after sampling, Method 0010 requires that the resin bed be maintained at

< 4 C until extraction to provide continue integrity of the resin and analytes on the resin.

To minimize the influence of ultraviolet light from breaking down the resin, we suggest that the resin cartridge always be wrapped in hexane-rinsed aluminum foil.  This protects the resin from harmful ultraviolet light, once again maintaining integrity of the resin.  The aluminum foil also minimizes contamination from hands on the resin cartridge.

The influence of oxidants has only recently come to light.  During sampling, we are pulling large volumes of stack gas containing many oxidants (i.e., oxygen, ozone, peroxides etc) through the resin bed.  It has been speculated that, during sampling, benzoic acid is produced as an artifact from the oxidation in the stack gases.  Polymers like XAD-2, because of their substituted benzene ring structure, slowly degrade and give off compounds like toluene, styrene, and similar compounds that oxidize to yield the benzoic acid during sampling.

For more information associated with semi-volatile monitoring and background concentrations of the XAD-2 resin, please contact Tom Ward, US Environmental Protection Agency, MD-74B, Research Triangle Park, North Carolina 27711 (919-541-3788).


  1. What do I watch for during the resin recovery involved in SW-846, Method 0010?


During the resin recoveries involved with both Method 0010 (Semi-VOST) and Method 0030 (VOST), observe how the resin beds are handled and stored.  Are they wrapped in hexane-rinsed aluminum foil to minimize outside influences of ultraviolet light, heat and external contamination?  Does each cartridge have a “Certificate of Cleanliness” associated with it’s paperwork?  Is each cartridge inscribed with a unique number/letter to identify that cartridge to that specific test run?  Is the field blank cartridge exposed to the same atmosphere as the sample cartridge during charging and recovering of the sample train?  During your review, observed if the cartridges are properly capped when not in use and that they are stored at < 4C at all times after sampling.  Observe that the Chain-of-Custody (COC) is properly filled out and the cartridges are properly identified on the COC.  Check to see when the cartridges were cleaned (should be on the “Certificate of Cleanliness” sheet and if the sampling date is within 30 days of that date (Both Method 0010 and 0030 require that the clean cartridges must be used within 30 days from cleaning).   Finally, if the cartridge is being used for dioxin/furan sampling (Method 0023A), then insure that proper field surrogates have been applied to the certified clean cartridge prior to sampling (remember, Methods 0010 and 0030 do not require field surrogates to be added to the sample cartridge).

For additional information concerning sorbent recoveries, please contact Mr. Gary McAlister, U.S. Environmental Protection Agency, MD-19, Research Triangle Park, North Carolina 27711 (919-541-1062).


  1. How important is the use of aluminum foil in the protection of the resin beds in SW-846, Method 0010 and 0030?


As discussed in Question #11, aluminum foil serves three purposes to minimize biases associated with Methods 0010 and 0030.  First, the hexane-rinsed aluminum foil prevents ultraviolet light from effecting the resin bed and analytes attached to the resin bed.  Second, the aluminum foil helps to minimize the influence of heat from either the sun or the stack.  In addition, the application of the aluminum foil helps to minimize influence of outside contamination on the walls of the cartridge.

Sometimes in stack testing, it is the small things that can add up to create large biases in the test data.  The aluminum foil helps us to maintain some small biases within our accepted control limits.


  1. How do I sample for chloroprene?


Chloroprene (C4H5Cl), 2-chloro-1,3-butadiene, has a vapor pressure of  226 mm Hg @ 25 C, a boiling point of 59 C, and a molecular weight of 88.5 g/g-mole.  As such, it is classified as a volatile organic compound (VOC).

Being a VOC, one would think that SW-846, Method 0030 would be the ideal choice for capturing chloroprene from stack gases.  Indeed, in lecture we identified Method 0030 applicable to those organic compounds with boiling points from 30-100 C, of which chloroprene certainly is a member.  However, if you review the paper Larry Johnson and I put together for the Title III HAPs (paper can be found in the Student Workbook), we identified chloroprene as questionable using Method 0030.  EPA has data that shows Method 0030 works well in the laboratory under control conditions for capturing chloroprene, but mixed results in the field.  It might be that chloroprene breaks through (low breakthrough volume) the Tenax and Tenax/charcoal traps in the Method 0030 sampling train or that oxidants in the stack gas reacts with the captured chloroprene on the resin bed, thus providing a negative bias to our concentration.  We really don’t know, but can only speculate.

However, EPA does have data to show that Method 0031 gives good results based upon a Method 301 validation.  Remember, Method 0031 uses three adsorbent traps (Tenax, Tenax and Anasorb-747).  Anasorb-747 is a carbon molecular sieve adsorbent, with large surface area and very amenable to capturing volatile organics.  Also remember that Method 0031 allows the sampling rate to be as low as 0.25 L/min, thus allowing considerable more contact time for the organic with the sorbent resins!

Consequently, the method of choice for quantitating chloroprene from industrial sources is SW-846, Method 0031.

Recently, EPA, Emission Measurement Center, Research Triangle Park, NC has posted on their web site ( relevant methods and procedures for emission testing and monitoring.  The web site is designed to provide the user guide in the application of stack test methods to specific analytes of interest.  The methods are presented under five (5) different categories.  The categories are based on a combination of (1) the legal status of the methods with regard to their application under federally enforceable regulations and (2) the validation information available on the method and the Agency’s corresponding confidence in application of the method for its intended use.


                Category A:  Methods proposed or Promulgated in the FR


These methods are used for compliance purposes under 40CFR 60, 61, and 63 by industrial sources.  These methods are being reviewed to meet EPA’s new format as recommended by the Environmrntal Monitoring Management Council (EMMC).


            Category B:  Source Category Approved Alternative Methods


These methods are approved alternatives to the test methods outlined in 40 CFR 60, 61, and 63.  They have been used by sources for determining compliance.  The Administrator has issued an official EPA letter stating the validity of the methodology as an alternative to the FRMs

            Category C:  Conditional Methods


These methods have been evaluated by the Agency and may be applicable to one or more source categories.  EPA has reviewed the method QA/QC, applicability to a source category, field and laboratory validation studies etc.

This method may be used by State and local programs in conjunction with Federally enforceable programs (e.g., SIP, Acid Rain, Title V Permits etc.).  The source must get approval as alternative before using to meet Federal requirements.


            Category D:  Preliminary Methods


The performance of these methods is not as well defined as those in the conditional category.  May be used in limited application as “gap filling” methods.


             Category E:  “Idea Box”


Methods concepts to promote information exchange.

Within each category, EPA provides examples of test methods for specific analytes.  For more information dealing with the application of source methods to specific analytes, contact Mr.  Tom Logan, US Environmental Protection Agency, MD-19, Research Triangle Park, North Carolina, 27711, 919541-2580.

For other applications of SW-846 methods in quantifying your target compounds, please contact Ms. Robin Segall, U.S. Environmental Protection Agency, MD-19, Research Triangle Park, North Carolina, 27711, 919-541-0893.


  1. Why is it necessary to purge the filter in the HCl/Cl2 train and why do a leak check in two sections?  Doesn’t this miss any possible leaks between the two halves (three-way valve) once reassembled?  Can a single whole train check be done instead?


As you recall, SW-846, Method 0050 was designed to sample HCl/Cl2 from hazardous waste incinerators and municipal waste combustors, especially suited for those sources with wet scrubbers emitting acid particulate matter (e.g., HCl dissolved in water droplets).  As such, Method 0050 requires isokinetic sampling to insure a representative sample is extracted from the stack.  The water droplets containing the dissolved HCl  would be extracted in a representative manner from the passing stack gas around the nozzle.  However, after the droplets enter the gas sampling train, they may fall out in the optional cyclone or be retained on the heated filter.  To address this bias, the method calls for purging the sample train for 30 minutes (purge air through an Ascarite tube) to vaporize the liquid and purge any HCl in the cyclone or retained on the filter and pull it through the train and into the first three impingers.  Recent test by EPA have demonstrated that if visible moisture is still in the cyclone or on the filter, then increasing the probe/filter assembly to 177 C with additional purging of 15 minutes will insure complete removal of the HCl from the cyclone/filter to the impinger system.

The two tier leak check procedure identified in Method 0051 (remember, Method 0050 requires a standard FRM 5 full train leak check) requires a leak check of the probe and three-way stopcock, then a leak check from the first impinger through the rest of the sample train. The two tier leak check would allow the stack tester to leak check the probe and three-way valve only one time.  The probe/valve assembly would stay in the stack until the end of the testing day.  This would allow the tester to run several test, exchanging out the impingers several times and leak checking the impinger/meter box only without removing the probe/three-way valve from the port.  This saves some time when multiple runs/tests are being performed at the source.

Indeed, a single whole train leak check can be done each time, which is stricter than what Method 0051 requires.

For more information associated with FRM 26, please contact Mr. Terry Harrison, U.S. Environmental Protection Agency, MD-19, Research Triangle Park, North Carolina 27711 (919-541-5233).


  1.  What are the differences between the different “blanks” discussed in lecture…lab, field, reagent, and trip?


There are several different “blanks” associated with stack testing methodology.  They are field, trip, reagent and laboratory blanks.  The objective of determining concentration of analytes in the different blanks is to verify the presence or absence of analytes, either those of concern [consequently, those on the target compound list (TCL)] or those analytes which might effect the results through positive or negative biases.

  • The trip blank is designed to identify levels of contamination from the exposure of the reagent or sorbent bed to the same atmospheres exposed to the analyte reagent or sorbent bed.  The trip blank is prepared in the laboratory with the other reagents or adsorbents prior to shipping to the field.  However, the trip blank is never exposed to the field atmospheres.  It is simply sent along with the field samples to and from the site.  The trip blank identified areas of exposure such as shipping temperatures and pressures, laboratory preparation of field samples and laboratory preparation of field samples for analysis.
  • The field blank is similar to the trip blank in that it is also prepared during the preparation of the field reagents or adsorbents.  However, the field blank is exposed to the same atmospheres in the field as the field samples.  This means that the field blank is opened during the charging of impingers or sorbents in the sample train.  The field blank is also exposed during the exchanging of cartridges in SW-846, Method 0030 or when field reagents are being exchanged during a test run.  In summary, field blanks consist of additional sample collection media (e.g., sorbent tubes, reagents, filters) which are transported to the monitoring site, exposed briefly at the site when the samples are exposed (but no stack gas is actually pulled through these blanks), and transported back to the laboratory for analysis, similar to a field sample.  At least one field blank should be collected and analyzed for each test series.
  • The laboratory blank is a sample of the reagents or sorbents used during the sample train reagent preparation or recovery.  The laboratory blank is a sample of the extraction solvent, the rinses used during sample recovery, or a sample from the batch of sorbent used to preparing sampling cartridges.  Laboratory blanks include both method blanks and instrument blanks.  method blanks are carried through all steps of the measurement process (from extraction through analysis).  A method blank is typically analyzed with each sample batch.  Instrument blanks are used to demonstrate that an instrument system is free of contamination.  Instrument blanks are typically analyzed prior to sample analysis and following the analysis of highly contaminated samples.
  • The reagent blank is a sample of the solvents used during recovery of the sample train after the test is completed.  You recall, reagent blanks for both multi-metal and chromium +6 require that the reagent blank be the same volume as the renses used to recover the samples, from probe to impinger.  This is because the blank value is substracted from the sample to obtain a final concentration.


  1. How does Method 0050 differ from FRM 26 or 26A for HCl?


SW-846, Method 0050 is an isokinetic sampling train for the determination of HCl/Cl2 from hazardous waste incinerators and municipal waste combustors, especially suited for those sources with wet scrubbers emissions of acid particulate matter (e.g., HCl dissolved in water droplets. As you recall, Method 0051 was designed for those stacks which were relatively dry, particulate free.  Must use Method 0050 at sources controlled by wet scrubbers that emit acid particulate matter and have water droplets.

Federal Reference Method (FRM) 26 is the same as SW-846, Method 0051 except  FRM 26 is for hydrogen chloride (HCl) emissions only (whereas Method 0051 can quantitate Cl2 also).  Finally, FRM 26A is different from SW-846, Method 0050 (both isokinetic), in that FRM 26A is applicable for determining emissions of hydrogen halides (HX) [specifically HCl, HBr, and HF], and halogens (X2) [specifically Cl2 and Br2].  Method 0050 only quantitates HCl and Cl2.


  1. Is the Ascarite purge in Method 0050 required for all runs?


As you recall, the objective of the Ascarite purge in Method 0050 is to move any entrained HCl/Cl2 on the heated filter or in the optional glass cyclone back to the impingers.  This is accomplished by attaching an Ascarite scrubber to the inlet of the probe, with the filter heated to 248 F, purging the train for up to 45 minutes at a desired flowrate of 1 inch of water as indicated by the delta H manometer.  EPA has found that if visible water is observed in the optional cyclone, one can increase the temperature of the filter box to 177 C to help vaporize the water, consequently moving the entrained HCl/Cl2 to the impingers.


  1. We see a lot of field blank contamination.  The stack test companies usually explain this a “laboratory artifacts” or “false positives.”  How much “blank contamination” should be accepted?


There is no general rule as for a acceptable blank contamination.  Of course, you do not want to have your target analytes as part of the “blank contamination” above the method detection limits (MDLs).

As specified in the individual methods, the following “blank contamination” levels are required to be met before the sorbent is allowed to be used in the sample train:

  • Method 0010 (Semi-volatile):  4 mg/kg of total chromatographable organics (TCO);
  • Method 0030 (Volatile):  2 ng/1.6 g of target specific analyte;
  • Method 0050 (HCl/Cl2):  Reagent blank less than 10 % of the sample values; and
  • Method 0060 (Multi-metals):  Reagent blank less than 2 ug/L of each target metals.


  1. In Method 0050, why use sulfuric acid to trap HCl (and how does it work)?  Why not use a base solution?


As specified in Method 0050, two impinger reagents are used to separate and trap HCl and Cl2 from the gas stream.  Acidic and alkaline absorbing solutions collect gaseous HCl and Cl2, respectively.  In the acidified water absorbing solution (i.e., 0.1 N H2SO4), the HCl gas is soluble and forms chloride ions by the following equation:

HCl  +  H2O  =  H3O+  +  Cl-

The Cl2 gas present in the emissions has a very low solubility in acidified water and

passes through to the alkaline absorbing solution where it undergoes hydrolysis to form a proton (H+), Cl-, and hypochlorous acid (HClO) by the following reaction:

H2O  +  Cl2  =  H+  +  Cl-  +  HClO

As you recall, sodium thiosulfate solution is added to the contents of the recovered alkaline absorbing solution ( e.g., 0.1 N NaOH) to stabalize the ClO- and removes the possibility of partial reduction of ClO- to Cl- and the resulting high bias to the results.

The resulting Cl- ions in the separate solutions are measured by ion chromatography by SW-846, Method 9057.  Those Cl- ions found in the acidified impingers are related to the HCl emissions and those in the alkaline impingers are related to the CL2 emissions.  Thus, through the selection of absorbing solutions and solubilities, we are able to differentiate between HCl and Cl2.

To use only a base wouldn’t allow us the ability to speciate and we would also have to change our analytical finish because of the many possbile reactions in the base impinger with absorbing HCl along with Cl2.


  1. Is the addition of a pH color indicator (~ pH 9 or 8) in the last NaOH impinger allowed in Method 0050/0051?


I have checked with EPA’s Emission Measurement Center (EMC) involving the addition of a pH indicator to the last NaOH impinger to show the visual change in color if the normality of the NaOH changes below 0.1 N (pH ~ 10).  EPA has not received request for approval of the methodology by adding a color indicator to the impinger.

However, thymolphthalein is blue at a pH of  > 11, but becomes colorless at a pH < 10.  I would see nothing wrong with adding a few drops of thymolphthalein in the last impinger as an indicator of pH change during sampling rather than stopping the test and having to leak check before checking the pH of the last impinger.  Of course, you must receive prior approval from the Administrator before implementation.

However, don’t forget our other options to maintaining proper strengths of our absorbing solutions:

  • Use stronger base (e.g., 0.5 N NaOH);
  • Add additional volume to the last impinger ( e.g., 200 mL); and
  • Recharge impinger during sampling.


  1. Why is FRM Method 18 not recommended for HAP testing?  Where could FRM Method 18 be used?


Federal Reference Method 18 was promulgated in the Federal Register,

48 FR 48344, October 10, 1983.  Since that time, the method has undergone corrections and updates.  On April 22, 1994, the method underwent an update for improving the quality assurance/quality control (QA/QC) sections of FRM 18.

When originally promulgated, the method was intended to be used as both a survey method to gain information as to what organics were being emitted from industrial sources and as input to agency models for regulatory activities.  FRM 18 is very similar to SW-846, Method 0040, Sampling of Principal Organic Hazardous Constituents from Combustion Sources Using Tedlar Bags.  Both methods are sample collection methods, with references to other FRM or SW-846 analytical methods for the analysis of the specific target compound list.  However, FRM 18 goes into great detail on how to analyze the survey Tedlar bag on-site by using various techniques for calibrating the gas chromatography system.

As identified in Section 2.1 of FRM 18, the “range of this method is from about 1 part per million (ppm) to the upper limit governed by GC detector saturation or column overloading.  The upper limit can be extended by diluting the gases with an inert gas or by using smaller gas sampling loops.”  Consequently, FRM 18 is truly applicable to those sources with emissions of gaseous organic compounds in the ppm range.  Since the method allows for “dilution” of the stack gas with inert gas using a Tedlar bag technique, the method is not sensitive to low ppb levels of organics.  As you recall in SW-846, Method 0030, we used a Tenax, Tenax/charcoal tubes to capture the hazardous organic constituents from the stack gas.  After collection, we performed a “thermal desorption” on the tubes to reach the desired detection limits needed for risk base calculations.  Those detection limits were in the 1 ppb range.  Whereas, SW-846, Method 0040 is in the 100s ppb range and FRM 18 in the 1 ppm range.


  1. What stack test method is used to sample diallyl phthalate (DAP)?


Diallyl phthalate (DAP) is a nearly colorless liquid, insoluble or limited solubility in gasoline.  It is soluble in most organic liquids.  It is a primary plasticizer for most resins.  It is a polymerizable monomer which will polymerize with heat and catalyst into a clear, hard, insoluble polymer.

Diallyl phthalate has a boiling point of 158-165 C ( 4 mm) and a vapor pressure of 1.5 mm at 150 C.  Diallyl phthalate is therefore defined as a “semi-volatile.”

SW-846, Method 0010 would be the best selection for a method to extract and quantitate diallyl phthalate from a source.  Since diallyl phthalate is not a traditional semi-volatile using Method 0010, I would suggest, as does the method, performing several laboratory evaluations of spiking known concentrations of DAP on clean, certified XAD-2 cartridges.

First set of experiments would to evaluate the extraction efficiency of XAD-2 releasing the DAP to the extraction solvent.  This experiment would require spiking three (3) XAD-2 cartridges with neat DAP (spiking in the center of the XAD-2 resin bed) at concentrations expected from the source.  You would then perform a normal Soxhlet extraction to determine the system efficiency (remember, the XAD-2 resin bed must also be spiked with the normal laboratory surrogates).  The recovery of the DAP from the XAD-2 cartridges must fall within Method 0010 surrogate recovery limits of 50-150 %.

The second set of experiments would involve spiking three (3) cartridges with the same level of DAP as used in the extraction experiment.  This time, the XAD-2 is challenged with clean, ambient air for the same sampling period as Method 0010 sampling time would require.  The XAD-2 cartridges would be recovered in the same manner, soxhlet extracted and analyzed by GC/MS.  Once again, the recovery limits would be 50-150 %.

During this experiment, you are determining whether the DAP will remain on the XAD-2 resin bed during sampling and whether there is any possibility of degradation of the DAP during sampling.

On the ambient side, we have excellent recoveries of DAP using combination of polyurethane foam (PUF)/ XAD-2 cartridges for trapping phthalates from ambient air.  Our laboratory experiments show an average of 92 % recovery for most of the phthalates.  Based upon that experience, I feel that SW-846, Method 0010 will be adequate for DAP.

(However, the phthalates can be a background problem for XAD-2 resin.  I would therefore suggest that you clean, certify the resin to show that you do not have phthalates as background concentration on the resin, but use the resin only once.  Use clean resin each time to minimize possible problems.)


  1. Shouldn”t the FRM 201A isokinetic be between 80-120 % rather than 60-140%?


FRM 201A does state that the allowable acceptable limits, Section 6.3.5, for isokinetics is between 80-120 % or that no sampling point be outside the delta p min or delta p max during sampling.

You will recall that FRM 201A is sampling at a constant rate through a PM-10 cyclone.  The objective of FRM 201A is to maintain the correct flow through the nozzle, consequently the PM-10 cyclone, to maintain the proper cut-side of the cyclone (9-11 microns) during sampling.  By not sampling isokinetically, as in Method 201, we are ignoring the larger particles.  Our assumption is that our bias will be small because we are only interested in the small particles (< 10 microns) which will follow the gas stream and enter our nozzle if we select a constant sampling rate that is close to 100 % isokinetics based upon the geometry of the cyclone and nozzle selection.  Maintaining the proper cut-size of the cyclone is the most important aspect of this method, not the % isokinetic limit.  Consequently, if I was reviewing a FRM 201A test report and they showed that the cyclone cut-size was maintained with the 9-11 micron size range, but isokinetics were 75 %, I would accept the test knowing that I am only interested in small particles (< 10 micron).  Remember, under isokinetics biases the mass emission high or in favor of the regulatory agency!


  1. If the KOH recirculation pump fails for a period of time (i.e., 20 minutes), must the test be invalidated for Method 0061?


YES!  Remember the function of Method 0061, Cr +6 sampling train, is to minimize the reactivity and conversion of Cr +6 to Cr +3 during sampling.  We learned in lecture that organics, oxidants and other chemicals can cause this conversion to occur in the impingers.  Consequently, in Method 0061 we inject the KOH at the outlet of the nozzle to quickly capture and stabalize the Cr +6 molecule before it has a chance to react with other chemicals.  This allows us to “fix” the Cr +6 molecule immediately when extracted from the source.  If we allow the pump to not circulate the 0.1 N KOH solution to the front of the probe, then the Cr +6 molecule has an opportunity to change before reaching the impingers.  Thus we aspirate the KOH into the front of the probe to capture the Cr +6 molecule.


  1. On Method 0061, can both chromium and Cr+6 be measured in the same test?  If someone wanted only total chromium, wouldn’t it be better to run the multi-metal train (Method 0060)?


SW-846, Method 0061, Determination of Hexavalent Chromium Emissions From Stationary Sources, is applicable for the determination of Cr+6  from hazardous waste incinerators, municipal waste incinerators, and sewage sludge incinerators.  With the approval of the Administrator, this method may also be used to measure total chromium.

For total chromium, you would operate the Method 0061 sampling train in the same manner for Cr+6, but would rinse all active components of the sample train (from probe inlet to the fourth impinger) with 0.1 M HNO3 for total chromium.  Remember, one filters the insolubles from the 0.1 N KOH recovered solutions and analyze the insolubles for total chromium also (along with the 0.1 M HNO3 rinses).  Consequently, the total chromium number would be the Cr+6 number plus the insoluble total Cr number plug the 0.1M HNO3 total Cr rinse.

For total chromium only, it would be easier to operate the multi-metals train (SW-846, Method 0060, without the KMNO4 impingers for Hg) rather than the Cr+6 train because of the special adaptor for the probe assembly and recirculating first impinger.


  1. Would you consider FTIR as an approved EPA method?  What is the reference to the EPA protocol?


Indeed, FTIR is a “main stream “ method for the EPA.  In support of the MACT regulations, EPA has promulgated and proposed several FTIR methods to help states determine whether sources are meeting their emission limits.  Under 40 CFR Part 63, Appendix A, we discussed the various FTIR methods applicable to state to use in their SIP programs as part of the MACT program.  If you remember in our “Sources of Test Methodologies,” Session 4, the 300 series found in 40CFR63 include the following FTIR methods:

  1. Method 320- FTIR Extractive Technique Applicable to Emission Sources

(Proposed March 24, 1998);

  1. Method 321- FTIR For HCl Emissions (Proposed March 24, 1998);
  2. Method 318- FTIR For Phenols, CO, COS, and Methanol (Proposed March 31,                 1997);
  3. Performance Specification Test (PST) 15- FTIR CEMS (Promulgated, Fall,                       1998).

Also remember, as part of The Compendium of Methods for Sampling and Analysis of Organic Compounds in Ambient Air-Second Edition, we have Compendium method TO-16 dedicated for the application of FTIR technology for monitoring organic emissions in the ambient air.  If you would like a copy of this method, just send me an e-mail.  I am the principle author of the Organic Compendium.

For more information about the applicability of FTIR to source emissions, contact Rima Dishskjian of EPA’s EMC at RTP (919-541-0443).



  1. Is stack velocity “directly” proportional to the absolute temperature, since PV=nRT?


Stack velocity is NOT directly proportional to absolute temperature.  The Ideal Gas Equation is PV=nRT, where “V” is volume of a gas in relationship to the temperature, “T” of the gas.

Velocity of a gas stream is determined by the following equation:

v =  KpCp [(Ts)(delta p)/(Ps)(Ms)]1/2


Now, Qs = (As)(vs) where As is the area of the stack and vs is the velocity of the stack gas.

The pmr (pollutant mass rate) = (cs)(Qs) where cs is the concentration of the pollutant (mass per unit volume) and Qs is the volumetric flow rate of the stack gas [(As)(vs)].


  1. Is there proof that benzoic acid is a byproduct of the degradation of XAD-2?

We do have several years of data showing that benzoic acid is a degradation product of the XAD-2 when exposed to stack gases.  Please refer to the answer to Question #11 for my explanation of the weaknesses of XAD-2 and how to minimize background contamination of XAD-2 in your sampling program.