STATE OF WASHINGTON DEPARTMENT OF ECOLOGY 

SOURCE TEST CALIBRATION METHOD V 

ECOCAL GENERATOR CALIBRATION 

I. Principle

The generator with the Ecocal permeation devices for H2S and SO2 are calibrated over 

the required ranges with gravimetrically calibrated Teflon permeation tubes traceable to 

NBS and Scott-Marrin certified gas standards. Wet chemical methods are used to provide 

alternate checks. 

II. Equipment

(1) Ecocal Model 202 calibration unit, with H2S and/or SO2 permeation units 

installed. 

(2) Barton Analyzer with pump, scrubber, and Teflon tubing. 

(3) IOC SO2 Analyzer. 

(4) Gravimetrically calibrated Teflon permeation tubes and Scott-Marrin certified 

gases. Constant temperature bath and gas dilution panel. 

(5) Teflon or Saran bags. Gas tight syringes. Calibrated wet test meter. 

III. Procedure

The Ecocal calibration unit is set up with the Barton Titrator and IBC Analyzer and 

connected to the gas dilution panel with teflon tubing and glass-teflon control valves. The 

constant temperature bath is allowed to come up to the specified temperature as is the 

Ecocal unit. Permeation tubes and devices are allowed to equilibrate until gas output is 

steady. 

(1) For H2S: 

The Barton Titrator is used to determine the output of the calibrated permeation 

tubes over the range of 0 – 60 ppm H2S. Concentration values of 20, 40, 60 and 

80% are sampled through the manifold and recorder values are tabulated with 

allowances for the instrument blanks between each point. 

Using Teflon or Saran bags of 10 liter capacity, aliquots of H2S (99.5%) are 

injected into the 10 liter measured amounts of scrubbed air with the gas-tight 

syringe. After a 15 minute equilibration period and manual mixing in the bag, the 

bag sample is attached to the Barton Titrator for measurement. Three samples are 

introduced at 30, 60 and 90% of the 0 – 60 ppm range. Recorder values are 

tabulated with allowances for blanks. The Scott-Marrin H2S tank value is also 

recorded after analysis on the Barton Titrator. 

In order to determine the accuracy and precision of the set of calibrated 

permeation tubes, a determination by the zinc acetate method of the concentration 

of the 40% value of the permeation tube standard atmosphere will be made. The 

procedure for the above method is attached as Appendix A. 
From the above data, a calibration curve is plotted for the Barton Titrator in the 

range of 0 – 60 ppm H2S. The Ecocal calibration unit is then connected to the 

output manifold of the dilution panel. Using the flowmeter of the Ecocal on the 

H2S channel, five points are recorded on the Barton recorder. Blanks are run 

between each point and an accurate value is determined for five metered flow 

rates through the H2S permeation device in the Ecocal unit. Using the following 

formula, a mean permeation rate is determined for the H2S permeation device. 

(Form, Appendix A) ~ 

P = ppm H2S x F

.759 

Where P = Permeation rate in ng/min. @ 37 degrees C 

F = Flow rate in cc/min. corrected for temperature and pressure. 

A calibration curve is plotted for the Ecocal permeation device for the various 

settings of the calibrator flowmeter. 

(2) For SO2: 

The IBC SO2 analyzer will be used to calibrate the Ecocal SO2 permeation device 

in the Tracor calibrator. High-emission Teflon permeation tubes are calibrated 

gravimetrically and by means of wet chemistry (Appendix C). Four 40 cm high 

emission SO2 permeation tubes are stored in a water bath and ventilated container 

for a period of two weeks, weighed twice weekly on a balance sensitive to 0.1 mg, 

and calibrated for emission rates by the formula: 

P = W1 -W2 

T 

Where P = Permeation rate in ng/min. 

 W1 = Starting weight in ng. 

 W2= Ending weight in ng. 

 T = Time elapsed in minutes 

Concentration of SO2 in a standard atmosphere can be calculated by the formula: 

 ppm SO2 = .382 x Permeation rate and tube length

Flow rate in cc/min. 

The IBC SO2 analyzer is connected to the manifold of the permeation tube water 

bath and dilution panel. Air flows are adjusted to give five concentrations of 20, 

40, 60 and 100% of the range from 0 to 1000 ppm SO2. These points are recorded 

and care is taken to run duplicates until a linear calibration curve accurate to plus 

or minus 10 ppm is obtained. A mean permeation rate is determined for the SO2

device. 

The IBC analyzer is now connected to the SO2 output of the Tracor calibrator. 

Flows are set on the flowmeter of the calibrator to provide six concentration 

values over the range of 0 – 1000 ppm. These values are tabulated on the 

procedure form (Appendix A), and compared with the calculated values. 
Wet chemistry determinations are performed on the concentration value of 

approximately 200 ppm SO2 from the Tracor calibrator. Duplicate runs are made 

by means of the Hydrogen Peroxide Method (Appendix C), and must agree within 

10 ppm of the values obtained by calculation of the permeation tube values above. 

A calibration curve is plotted of various settings of the calibrator flowmeter. 

IV. Calculations 

The procedure form is completed for the two gases and the values recorded from 

the H2S and SO2 analyzers. Two calibration curves are provided for the Tracor 

calibrator. The curves will show the gas, S/N, and permeation rate of the devices 

installed in the calibrator, as well as a table of H2S and SO2 ppm values for 

flowmeter settings of the Tracor calibrator flowmeters. 
Ecocal Generator – H2S and SO2 

Procedure Data Form 

H2S 

Permeation Tube Barton Analyser

Std. Atmospheres Blank Recorder

 ___________ __________ 

 ___________ __________ 

 ___________ __________ 

 ___________ __________ 

H2S 

Bag Standards Conc.

 ____________ ___________ __________ 

 ____________ ___________ __________ 

 ____________ ___________ __________ 

H2S 

Scott-Marrin Certified 

 Tank Gas No. _________ ___________ __________ 

Conc. ________________ ___________ __________ 

Zinc Acetate H2S Method 

Std. Conc. 1) _____________ Analysis 1) ______________ 

2) _____________ 2) ______________ 

Permeation Rate 

 Tracor Device s/n ________ ______________ ng/min 

 
H2S Calib. Curve 

Flowmeter Barton Analyser 

Reading Flow Rate Calculated Concentration Blank Recorder

1) __________ ___________ ___________________ __________ _________ 

2) __________ ___________ ___________________ __________ _________ 

3) __________ ___________ ___________________ __________ _________ 

4) __________ ___________ ___________________ __________ _________ 

5) __________ ___________ ___________________ __________ _________ 

6) __________ ___________ ___________________ __________ _________ 

SO2 Calib. Curve – IBC Analyser 

Bath Temp. __________________ 

Perm. Tub Nos Perm. Rate Flow Rate Calc. Concentration IBC Recorder 

_____________ __________ __________ ________________ _______________ 

_____________ __________ __________ ________________ _______________ 

_____________ __________ __________ ________________ _______________ 

_____________ __________ __________ ________________ _______________ 

SO2 Tracor Device Calibration Curve Tracor Calibrator s/n________________ 

Flowmeter 

Reading Flow Rate Calculated Concentration IBC Analyser Recorder

1) __________ ___________ ___________________ ___________________ 

2) __________ ___________ ___________________ ___________________ 

3) __________ ___________ ___________________ ___________________ 

4) __________ ___________ ___________________ ___________________ 

5) __________ ___________ ___________________ ___________________ 

6) __________ ___________ ___________________ ___________________