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.
########################################################################
To unsubscribe from the AIRQUALITY list, click the following link:
https://www.jiscmail.ac.uk/cgi-bin/webadmin?SUBED1=AIRQUALITY&A=1
|