Positioning and Placement of Gas Detectors

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 here

 Perhaps the most difficult task of any project that involves gas monitors and gas detectors is to decide on the placement of the various detectors and monitors. Even with all the new software( and all the associated bells and whistles) available now, it is more of an art than a rigid science.  Some questions that need answering before you start the job are

1. How do you estimate where the leak would likely take place? From flange joints in piping? Or from valve stems/packings? Or from sampling points? Or from reactor agitator shafts (even with all the mechanical seal stuff)?
2. Once leaked, how would the gas flow? How will the molecules move in the air? We can study gas dispersion models of leaks, but they are not accurate predictions. Would the gas flow just as the dispersion model says it should? Or will it flow in some other pattern?
3. How much would reach the detector?
4. Would the detector sense it? (Would the sensor be "alive" or already poisoned to death a long time back?

Only then can we start siting the detectors. This is of course after the technology has been selected (InfraRed or Catalytic Combustion or Semiconductor or other).