Hi All,

Recently we have employed passive AQ monitoring by Tenax tube along side continuous monitoring by PID at a sensitive site subject to a heating fuel leak.  

For the next round of monitoring I am considering passing the exhaust of the PID through a Tenax tube to obtain concentrations from the Tenax results rather than masses, "actively" monitoring by Tenax rather and passively.

I assume that thermal desorption tubes have a capacity; therefore, how long it would take to reach that capacity will depend on the concentration of VOCs present and the volume of air passed through.

Across a week of monitoring the PID data (as isobutylene, 10.6 eV lamp, pump rate 405-550 cc/min.), the location with the greatest concentration of VOCs varied between 0.7ppm and 29.8ppm (minimum and maximum readings), average readings per minute varied; 0.8ppm to 27.8ppm, the median at 9.7ppm.  Total mass of top 10 TICs from Tenax analysis at the same location 9730ng.

Does the forum know, what the capacity of a Tenax tube is?  Is it dependant on the compounds present?  In a situation such as the above, roughly, how long would a tube be on site for before reaching capacity?

I look forward to your responses.

Thanks in advance,

Peter.

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