                           Protocol for Conducting 
               Laboratory Testing of Portable Clearance Devices 
                       with Sulfuryl Fluoride Standards
                          Revised: September 3, 2019
                        (Corrected: December 30, 2019)

   Analytical Chemistry Branch (ACB), Office of Pesticide Programs, U.S. EPA

 Objective
      To evaluate the performance of portable sulfuryl fluoride monitoring devices at different sulfuryl fluoride (SF) levels, particularly the reliability of detecting SF at the safe entry level of 1 ppm.

 Portable Monitoring Devices
      Duplicates of four different types of portable SF monitoring devices are used in this study.
 Spectros' SFExplorIR, obtained through a vendor, Univar
 Messtechnik's CLIRCheck, obtained through Cardinal Professional Products
 Interscan's GF1900, obtained from Interscan
 Uniphos' Fumispec-Lo, obtained from Uniphos Envirotronic Pvt. Ltd.
      All devices are received pre-calibrated by the vendors. The recommended re-calibration interval, based on the information contained in the device's manuals, is 3 months for the GF1900 device, 6 months for Fumispec-Lo, 12 months each for the SFExplorIR and CLIRCheck.   The calibration interval is corrected by the manufacturers to one month for GF1900 and one year for Fumispec-Lo.  Table 1 lists the SF devices used by ACB and their calibration dates.
      
 Sulfuryl Fluoride Gas Standards
      Table 2 and Table 3 list the different levels of SF tested.  Certificates of Analysis (COA), dated September 7, 2018 for those in Table 2 and April 24, 2019 for those listed in Table 3, are provided by the supplier, Praxair, for each tank.  
      
      
      
      
Table 1: List of SF portable monitoring devices
Manufacturer
Model
Serial #
Manufacturers Recommended Calibration Interval
Calibration Date(s)*

Spectros Instruments

SFExplorIR

18066096

12 months

8/2/2018, 5/31/2019
Spectros Instruments
SFExplorIR
18066324
12 months

9/10/2018, 6/3/2019

Interscan Corporation
GF1900
025656
1 month
8/23/2018, 11/26/2018, 4/16/2019, 6/21/2019, 7/10/2019, 8/9/2019
Interscan Corporation
GF1900
025682
1 month
10/8/2018, 11/20/2018,  3/20/2019, 6/20/2019, 7/10/2019, 8/9/2019

ppm Messtechnik GmbH 
M.A.C 2640 CLIRCheck
5572 (replaced with 5740)
12 months
9/6/2018,  12/20 2018, Replaced on 6/10 2019
ppm Messtechnik GmbH
M.A.C 2640 CLIRCheck

5536
12 months
6/27/2018, 5/21/2019
Uniphos Envirotronic Uniphos Envirotronic
Fumispec-Lo 
Fumispec-Lo
1118018
1118020
12 months
12 months
1/2/2019
1/2/2019
*The dates are initial calibration, re-calibration or repair/recalibration dates.  Additional calibrations will be performed as needed.  The monthly calibration of GF1900 is performed by ACB only when the device is being used.




Table 2. List of SF gas standard tanks (from Praxair) made in N2.  
Nominal Concentration
                        Certificate Value (ppm) (+-1%)
                                     Lot #
                                     1 ppm
                                     0.914
                                  70577823602
                                     3 ppm
                                     2.813
                                  70577823603
                                     5 ppm
                                     4.82
                                  70577823604
                                    10 ppm
                                     9.53
                                  70577823601
      2200 PSI, 165 ft[3] tank.  
Table 3. List of SF gas standard tanks (from Praxair) made in air.  
Nominal Concentration
                        Certificate Value (ppm) (+-5%)
                                     Lot #
                                     1 ppm
                                     1.14
                                  70577910203
                                     3 ppm
                                     3.04
                                  70577910503
                                     5 ppm
                                     5.09
                                  70577910504
                                    10 ppm
                                     9.67
                                  70577910501
      2200 PSI, 83 ft[3] tank. 

      Note that the actual certified concentration of SF gas in each tank is slightly different from the nominal value.  The certified concentrations are in ppm (technically in ppmv).  The SF gas is supplied in compressed gas tanks in N2 (Table 2) and in purified air (Table 3). 
      To address comments from the Review of Report: Performance of Devices used to Measure Sulfuryl Fluoride Re-Occupancy Threshold following Structural Fumigation, by R.H. Sheffrahn, H.H. Hochmair, B. Gillenwaters, and J. Warner, January 2018, Prepared by Douglas Products (Sept 2018) and the comments from Douglas Products on the draft version of this protocol (5/28/2019) that the SF gas standard should be in air and the "zero air" and SF standard must be at same humidity and temperature levels, the SF standards made in filtered air (Table 3) will be used as the primary standards for the testing of the clearance devices at concentration levels listed in Table 3.  
      Several twenty-liter (20 L) capacity Kynar Dual Valve gas bags (Cole-Parmer, Cat #01410-54) are used to collect the SF gas standards from the compressed tanks, via stage regulators, tubing, and a release needle.  Each bag has one port with a septum for using syringe and one port with an on/off valve for connecting a tubing.  The bags are labeled with the nominal concentration of the SF and are only used for that SF concentration level.
      Each bag is evacuated with a gas-tight syringe to remove any air in the bag before being filled with the SF gas from individual tanks.  The bags are filled partially (i.e., the gas pressure inside the bags would be at ambient atmospheric pressure).  The testing device is connected to an SF gas bag with a quick-connect (1/4)" compression connector via a 2 inch-long teflon tubing to the on/off port during the test.
      Additionally, several twenty-liter (20 L) capacity Kynar Dual Valve bags are used to collect dry air from a compressed air tank through a stage regulator and a drierite gas desiccant tube (Cole-Palmer, Cat. #27068).  These bags of air are used as zero-air during the warmup of the devices and in between the tests. 
      Fresh SF gas standards are collected in the Kynar gas bags for each day of testing after the devices are warmed up and are ready.  The level of the SF collected in the Kynar bag is also monitored with a gas chromatography/mass spectrometry detector (GC/MSD) on testing days periodically.  Procedure for the GC/MSD analysis is described in the section of "Specific Operation Procedures." 
      
 Measurement of SF Level
      
      The objective of this laboratory study is to test/use the devices  in a manner, as close to a typical field user as possible, to evaluate the performance and reliability of the SF monitors to different levels of SF concentrations present in air.  The device is exposed to a SF gas bag and fresh air alternatively after taking a reading, as in the field, except that the device is stationary on the laboratory counter, while the SF gas bag is connected or removed.  The devices are plugged to electric power supplies and the batteries are fully charged before each use. 
      The tests are conducted in the laboratory under ambient conditions.  The room temperature and humidity are monitored with a portable temperature/humidity meter (NIST traceable) and recorded in a lab notebook on the days of testing.  The devices are operated according to the instructions provided in their corresponding manuals.   The specific steps for each device are summarized in the section of "Specific Operation Procedures." 
      A dry air bag is connected to the device before it is turned on.  Upon warming up and the devices are in "Ready" status, the readings of the devices are zero (clean air reading).  For GF1900, the display is then zeroed manually with the zero-adjusting knob after setting the reading to 20 ppm until stable (details in the section of Specific Operation Procedures).  For SFExplorIR, the purge bag is filled with clean air (dry air, or lab fresh air, or N2 collected in a 20 L gas bag from a compressed N2 tank in some comparison tests.  See "Comparison Tests" section) by pressing "Enter."  For tests conducted with dried air, bags of air collected from a compressed tank, after passing through a drierite desiccant tube, will be used for zeroing during the warmup process before the tests and in between tests.
      The ventilation and air circulation system of the laboratory is set to replace the air in the entire room with outdoor air at a rate of 20-25 times/hour.  The filling of the SF gas bags from the compressed tanks is conducted in a fume hood.  The gas bags are stored in the fume hood when they are not in use. The valve on the SF gas bag is closed before removing from the clearance devices.  
      The tests are repeated twice a week over a period of three months, each time with freshly prepared SF gas bags, for a total of approximately 280 measurements.  The tests are conducted in triplicates at each SF concentration for each device, one device at a time.  The tests for all the devices at all four SF concentration levels are conducted in one day for each test episode.  Additional measurements under different conditions will be conducted to further evaluate the performance of the devices (see "Comparison Tests" section).
      If a device malfunctions and cannot be corrected by ACB, the manufacturer will be contacted to repair the device.
       
 Comparison Tests

  Test under different relative humidity conditions
      One concern raised by stakeholders is that the difference in the relative humidity of the fresh air bag and that of the SF gas could affect the performance of the devices.  Though the room temperature is controlled to 21[o]-22[o]C throughout the year, the relative humidity in the air may change depending the season and weather conditions.  It has been recorded that the relative humidity in the laboratory could vary from about 5% to 55% throughout the seasons and weather conditions.  The relative humidity in the SF gas tanks is near zero.  As a result, comparison tests will be performed on multiple days of high humidity.  One set of measurements will be conducted with the high humidity lab air as fresh air for zeroing the devices (all devices) and fill the purge bag (SFExplorIR).  Another sets of measurements will be conducted with dry air (passed through a drierite desiccant tube, Cole-Parmer, Cat. #EW-07193-00) collected in a 20 L Kynar bag from a compressed air tank as the fresh air for zeroing the devices.  The measurements will be compared.       
	Because the SF standards are in dry air, results from tests with dry air as the zero air will be primary data to be used for evaluations.

  SF gas made in N2 vs. SF made in air
      One set of SF standards is made in N2 by Praxair.  A second set of SF standards is made in filtered air.  Tests will be conducted with both sets of SF standards on the same day.  The results will be compared to see if the inert gas (N2 or air) would make a difference in the performance of the devices. 
      Additionally, the measurement results would verify if there is any error in the concentrations of the two sets of SF standard during preparation.  The SF concentrations in the tanks are also verified with SF standards prepared at ACB with a GC/MSD.
 
  Evaluation of calibrations
      All the devices are received pre-calibrated by the vendors/manufacturers.  The tests will be conducted within the valid calibration date.  The devices will be sent back and re-calibrated, even if they are still within valid calibration date and no issues are found in the responses to SF, by the authorized vendors or manufacturers, after acquiring sufficient amount of measurement data.  Additional tests will be conducted under similar conditions with the re-calibrated devices.  Each re-calibration is documented with a date and the name of the person/company performing the calibration.

 Documentation

	The temperature and relative humidity of the room will be monitored by a portable device and recorded.  Preparation of SF gas bags, the individual readings and status of each device during the tests will be recorded in a test logbook for each device.  The time required to reach stable maximum reading when exposed to SF and that required to return zero after removing the SF will also be recorded.  The stable reading is defined as the reading remains unchanged in a 10-15 second period. 
      The date, starting time, and end time for the tests will be noted in the data entry logs for each device.  Unexpected observations during the tests will be noted as well.
      Reasons for possible repair services and calibrations (internal or by manufacturers or by the authorized vendors) of the devices will be documented.  Any deviations from the written procedure, any errors or abnormal performance and corrective actions taken will be documented.
      The actual readings on the devices (without regard to the significant numbers of the display) will be recorded for the measurements of SF levels for each device.  For the GF1900, the reading is estimated to the nearest reading of half point, e.g., 1.5, 2.0, or 11.5, because of the analog display.  The monthly calibrations while the device is in use will be recorded in the data entry logs.
        


                        Specific Operation Procedures 
        (adapted from the instructions of each device's user manual)

Spectros SFExplorIR:

    Fully charge the battery by connecting the power to an outlet
    Connect the battery to the device and turn on the device.
    If using a bag of dry air as zero-air, connect the bag of air to the device, open the gas valve, and then turn on the device.
    Verify the devices go through the warm-up procedure properly.  If there is any error/fault, record the error and follow the instructions in the manual on how to handle the errors.  After the warm-up, press the "ENTER" to fill the purge bag with zero-air.
    To measure the SF level in the bag, connect the partially filled 20 L SF gas bag to the device with a quick-connect tube while the display is in "Measure" and open the valve on the SF bag at the same time.
    Record the reading after it reaches a stable reading.  Typically, it reaches a stable reading in 3 to 5 seconds.  The measurement is automatic and continuous. Wait for 5 to 10 sec. to ensure the reading is stable.
    Close the valve and disconnect the bag from the device.  Record the reading (should reach zero, in a few seconds).  Keep the SF bag in fume hood when not in use.
    If zeroing with air bag, connect the dry air bag immediately after removing the SF gas bag and open the valve on the air bag at the same time.
    Repeat the test in triplicates.
    Wait if the device is in purge mode.  The device performs purging with internal purge-air bag automatically every 3-4 min.  Measurement resumes automatically after purging.
    Test the device with different bags of SF gas at different concentrations.
    When the message "Purge Air Empty" appears, take the device to another room with no SF containers present and then press the "ENTER" to refill the internal bag, if using ambient air as zero-air.  Or connect a Kynar bag filled with  dry air (filled from compressed air tank) to the device and refill the purge bag from that bag.
    Turn off the device by press the "On/Off" button after the completion of the tests. 
    Stop the measurement if there is an error/fault message on the device.  Investigate the causes and correct the errors.  Contact the vendor if necessary to resolve the error.  


M.A.C 2640 CLIRCheck

 Fully charge the device or plug to wall outlet.
 Press "On/Off" to turn on the device.  If using dry air bag as zero air, connect the bag of air to the device and open the valve.
 Wait for the self-test, the warm-up and auto zeroing to complete.
 Press "Start" to start the measurement.  The internal pump will continue to operate after "Start" is pressed.  It should read "0 *" when no SF was present.
 Connect the partially filled 20 L SF gas bag to the device with a quick-connect tube and open the valve on the bag at the same time.
 Wait for the reading to stabilize (typically reaches the maximum reading in 30-50 sec.).  Wait for additional 10 to 20 sec. to ensure the reading is stable.  
 Record the reading and then disconnect the bag from the device. Close the bag valve.
 If zeroing with a  dry air bag (filled from a compressed gas tank), connect the gas bag to the device immediately after removing the SF gas bag and open the valve on the air bag at the same time.
 Record the time for the reading to return to zero.  
 Repeat the test in triplicates.
 Press the "Start" again to put the device to standby.  After a few seconds the internal pump will stop and "Standby*" message will be displayed.
 After the tests are completed, press and hold "On/Off" for a few seconds to turn the device off.
 Stop the measurement if there is an error/fault message on the device.  Investigate the causes and correct the errors.  Contact the vendor if necessary to resolve the error.  

Interscan GF1900:

 Fully charge the battery or plug the power cord to a wall outlet.
 Turn the function knob to "On".  If using a bag of dry air as zero-air, connect the bag of air to the device and then turn on the device.
 Make sure the oven switch is on (downward position under the red cover).
 Wait until the "Ready" light is on.
 For best results (to prevent zero drift) the first time the monitor is used during the day, set the meter to 20 after the READY light is ON. If the meter is moving up or down, wait until it stops.  
 Adjust the zero knob to zero on the display.
 Connect the partially filled SF Kynar bag to the air inlet tubing and open the valve on the bag at the same time.
 Wait until the reading stabilize and record the reading.  Typically, it reaches stable readings between 30 seconds to 2 minutes.
 Disconnect the SF bag from the device and wait for the reading to return to zero.
 If zeroing with a dry air bag, connect the air gas bag to the device immediately after removing the SF gas bag and open the valve on the air bag.
 The zero may need to be adjusted only if the display does not return to zero after 30 min in clean air environment.
 Repeat the test by following steps from (5) through (9).
 Turn off the device by turning the function knob to "Off" after the tests are completed.
 Stop the measurement if there is an error/fault message on the device.  Investigate the causes and correct the errors.  Contact the vendor if necessary to resolve the error. 
GF1900 Calibration 
      The GF1900 needs to be calibrated monthly, which can be performed by the user. 
      Before each use, check the last calibration date in the lab data entry log.  If it is more than 30 days since the last calibration, perform calibration with 5 ppm SF gas standard.
      After the device is warmed up, "Ready" light is on, and the reading set to zero with "Zero" control (see Step 5 and Step 6 in above section), connect a Kynar bag filled with 5 ppm SF gas standard and turn on the valve of the gas bag.  Leave the bag on for at least 3 min.  
      Use a small flat screw driver to adjust the "Cal" control, which is located under the sticker over "Cal", to adjust the reading to the exact SF standard concentration.
      Disconnect the SF gas bag.  Let the device stabilize in clean air for 3 min.  Do not adjust zero.
      Repeat the procedure two additional times. The calibration procedure can also be found on YouTube: https://www.youtube.com/watch?v=I6O10b8FcIs. 
      Document the calibration in the lab data log.
   
   
Uniphos Fumispec-Lo

 Fully charge the device or plug to wall outlet.
 Press and hold "Power" button for 5-10 sec. to turn on the device.  If using a bag of dry air as zero-air, connect the bag of air to the device, open the valve, and then turn on the device.
 Wait for the self-test, the warm-up, initialization, and auto zeroing to complete.
 The screen will display "Measure".  If different displays are shown, press up or down arrow button to change the display to "Measure".
 Press the "◄┘" button (the "enter" button) to start the measurement.  The device will check the flow of air and display "Flow is OK" before displaying the reading.  It should read "< 001 ppm" when no SF is present.
 Connect the partially filled 20 L SF gas bag to the device with a quick-connect tube and open the valve on the bag at the same time.
 Wait for the reading to stabilize (typically reaches the maximum reading in 20-40 sec.).  Wait for additional 10 to 15 sec. to ensure the reading is stable.  
 Record the reading and then disconnect the bag from the device.  Close the bag valve.
 If zeroing with an  air bag (filled from compressed gas tanks), connect the gas bag to the device immediately after removing the SF gas bag and open the valve on the air bag at the same time.
 Record the time for the reading to return to zero.  
 Repeat the test.
 Press the "●" button to put the device to standby.  After a few seconds the internal pump will stop and "Measure" message will be displayed.
 After the tests are completed, press and hold "Power" button for 5-10 seconds to turn the device off.
 Stop the measurement if there is an error/fault message on the device.  Investigate the causes and correct the errors.  Contact the vendor if necessary to resolve the error.  

Operation Procedure for GC/MSD Analyzing Sulfuryl Fluoride Gas
      
      An Agilent 6975 gas chromatography/mass spectrometry detector (GC/MSD) or equivalent with a  30 m x 0.25 um, 0.25 um film thickness DB-5 column is used for the analysis.  The temperature is programed to increase to from 40[o]C to 100[o]C at a rate of 10[o]C/min after holding for 1 min at 40[o]C.  Manual injection using a 50 ul gas tight syringe is used for SF gas samples.  The MSD is operated under select ion mode with m/z 83, m/z 102, and m/z 67 being monitored for SF. 
      Vikane(R) (99.8% SF, Dow AgroSciences LLC, Indianapolis, IN, USA) from a compressed gas cylinder was released into an evacuated Tedlar(R) gas bag ( Restek).  From this stock, 40 ul of SF was withdrawn using gas tight syringes and placed into another tedlar bag that contained 100 ml of purified air.  The concentration of SF in this bag is calculated to be 1429 ppm (weight/weight).  
      
      The calculations are based on the ideal gas properties at 22[o]C and 1 atm pressure, using the density of SF gas of 4.2115 g/L and the density of air of 1.1791 g/L under these conditions.  Various amount of this stock standard at 1429 ppm (weight/weight) is then withdrawn and placed into additional tedlar bags filled with known amount of purified air to obtain known concentrations of SF calibration standards by dilution (see Table below).  The calibration standard of SF is prepared in the range of 0.27 ppmv to 10.98 ppmv.
      
      
                   Calibration Standard Concentration (ppm)
          Amount (ml) transferred from stock (1429 ppm) to 200 ml air
                            SF concentration (ppmv)
                                     1 ppm
                                     0.14
                                     0.27
                                     1 ppm
                                     0.42
                                     0.82
                                     3 ppm
                                     0.69
                                     1.37
                                     5 ppm
                                     1.37
                                     2.75
                                    10 ppm
                                     2.75
                                     5.49
                                    20 ppm
                                     5.49
                                     10.98
      
      
      Ten microliters (10 ul) of the prepared SF calibration standards and the SF gas collected in the 20 L Kynar bags were injected on to the GC/MSD manually using a 50 ul gas tight syringe.  Triplicate injections were made for each calibration standard and SF gas sample.  
      
      After the initial analysis and verification of the concentrations of SF gas in the compressed tanks, the concentrations in the collected gas bags will be analyzed periodically on testing days to ensure the SF gas is stable and the concentration remain unchanged.
      


