A PID may not pick up less volatile components of your hydrocarbon. If
the hotspot you mention was diesel or oil and is quite old the PID will
have little chance of finding anything. An FID might pick more up - your
gas meter is probably an FID, but calibrated to methane. A gresham
tube or tedlar bag sample submitted to the lab for a detailed
hydrocarbon suite should clear the matter up.
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