Skip to main content

Logo for N.C. Cooperative Extension N.C. Cooperative Extension Homepage

Monitoring Flue-Cured Tobacco Barn Heat Exchangers

The US Tobacco Good Agricultural Practices (GAP) Program established the requirement to assess heat exchangers within flue-cured tobacco barns for potential combustion products leaking into the curing chamber. Primarily, industry is concerned with tobacco specific nitrosamines (TSNA). Carbon dioxide, while not related to the formation of TSNA, has been proven to be a reliable indicator of heat exchanger leaks. Thus carbon dioxide meters are used to test heat exchangers for potential leaks. The US Tobacco GAP practices require that this testing be performed at least once every three years.

This requirement applies to all barns used for curing. Specific information such as the carbon dioxide probe’s serial number, equipment calibration documentation, barn identification number and location of barns, as examples, must be recorded during the testing. This information must be supplied to the contracting purchaser of tobacco upon request. Failing barns may be repaired and retested until properly functioning or placed out of service by removing all utility connection.

Tobacco producers are allowed to test their own barns as long as the test is performed with the recommended equipment. A list of approved equipment and company contact information is provided below. If preferred, a tobacco producer may hire someone that has been certified to test barns. Only companies/individuals trained and certified by N.C. Cooperative Extension have been sanctioned by the US Tobacco GAP Program to perform this test. (Individuals wishing to obtain certification and training should contact their local Extension office).

2 Meter Equipment Recommendations

Resolution:                           1 ppm CO2                                                                                                        Accuracy:                              ± 50 ppm CO2                                                                                            Measurement Range:         0-6000 ppm CO2 (or less if available)                                                  CO2 Sensor Calibration Certificate (Available from manufacturer and must be recalibrated based upon manufacturer recommendations)

Company Contact Information

Commercial low concentration CO2 meters are available. Vaisals CARBOCAP GM70 or GMT222, Testo 535 and Extech EA80 are examples. However, not all equipment is the same. As example, the Extech EA80 does not include a remote sensing probe and as a result, direct observation/reading is not possible during the procedure. Examine the features and cost to fit your situation prior to purchasse. Below is a listing of contact information to purchase these meters.

 Vaisala Inc. Testo, Inc                                   Extech Instruments

10-D Gill St                                 40 White Lake Road                     9 Townsend West

Woburn, MA 01801                    Sparta, NJ 07871                          Nashua, NH 03063

Phone:  (781) 537-1058            Phone:  (800) 227-0729                Phone:  (877) 439-8324                       

Companies and individuals certified by N.C. Cooperative Extension for flue-cured tobacco heat exchanger testing can be found at the NCSU Tobacco Information Portal at