In case of IR based LEL detectors which mounting is better Horizontal or Vertical and why?

 

The IR LEL detector that I recently pulled data from had a specific statement in the manual that the sensor had to be mounted in a vertical position (vertical cylinder).

Its threaded connection on the top connects to a threaded port on the bottom of the electronic transmitter housing.

That attitude would limit water/rain entry into the sensor, but I do not know if there are other reasons.

No reason was given in the manual for the mounting requirement.