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Users of the Thermo Scientific 1405-F TEOM Continuous Ambient Air Monitor and 1405-DF TEOM Continuous Dichotomous Ambient Air Monitor may need to review your instrument temperature settings as your seasonal ambient conditions change.
Keeping track of the dryer dewpoint(s) is key. When the dryer dewpoint(s) approach the cooler temperature(s), the potential for condensate forming inside the instrument exists. Seasonal ambient conditions can influence the instruments ability to maintain the sample dewpoint and the monitor can become unstable resulting in fluctuations of MC and or system status conditions. Some users may need to adjust the instrument temperature zone settings because of these changes in seasonal ambient conditions. The instrument temperature zone settings can be set between 30°C and 40°C. The election of the setting should be based upon local meteorological conditions, comparison with local gravimetric sampling results and local regulatory guidelines. The heated section of the instrument has an effect on the dryer’s ability to maintain relatively stable sample dewpoints. The sample dewpoint will trend with changes in ambient dewpoint levels.
Users might have concerns about changing these settings, but as long as your results meet the regulatory criterion and compare with gravimetric results the instrument is fine and operating within the approved standards.
The cooler temperature can also be set to either 4°C or 10°C. A monitoring station experiencing above average ambient dewpoints and have maximized the instrument temperature settings may need to go with 10°C chiller settings to augment the optimal instrument performance.
Condensation can also be prevented by insulating any exposed sample lines above the FDMS module inside the shelter.
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