A maintenance worker stands above an open manhole, peering down into the dark confined space below. Even using his flashlight he cannot see the bottom of the pit, so he has no way of knowing if it is dry or if there is water in the bottom. More importantly, he does not see the unforeseen gas hazards that may be lurking below. He slowly lowers a sampling tube connected to a gas monitor into the area to detect if any hidden dangers await.
At the same time, 200 miles away, a maintenance worker is walking through a chemical refinery, inspecting pipes and valves for leaks. Many of the joints and valves that are being inspected are 10-15 feet high, requiring the worker to use a sampling probe to search for the leaks.