Customer Mike recently sent me an email stating that he had been told by someone that the type of sample tubing that he used could affect the readings that he gets on his gas monitor. He wanted to know if this was true.
Well Mike, and everyone else, this certainly is true. The type of sample tubing you use in conjunction with your gas monitor in remote sample applications and even during calibration can have a very pronounced effect on the gas readings that you obtain. Not all sample tubings are created equal. Certain types of tubing will react with certain gases and therefore negatively impact the accuracy of the monitor readings in different ways.
For instance, silicone rubber tubing and other types of tubing that contain silicone should never be used with a gas monitor that has a catalytyic bead combustible gas sensor. The silicone vapors that may be off-gassed from the tubing will react and quickly poison the sensor reducing its sensitivity and ability to accurately detect combustible gas.
PVC tubing, such as the flexible tubing that the industry commonly refers to as Tygon tubing, may be suitable for sampling common gases such as oxygen, carbon monoxide, hydrogen sulfide and typical combustible gases that are measured at percent LEL levels, but PVC tubing can also react with many VOCs and other gases such as chlorine or ammonia and reduce the concentration of the gas that ultimately reaches the sensor in your gas monitor. A polyurethane based tubing may be more suitable for some reactive gases but may still be prone to attracting moisture in humid environments that will react with and reduce the sampled gas concentration.
My advice to Mike, and to anyone using a portable gas monitor, is to use tubing made of a high quality, non-reactive material for remote sampling and calbration in any application where gases of a highly reactive nature are being measured in low concentration. The most suitable tubing for reactive gas applications would be constructed of a Teflon (PTFE) based or Teflon-lined PVC material.
The type of tubing you use does and will make a difference, keep it high quality and you will keep it safe!