The object is to lead you to or find the place of the leak. No leak is OK in a home, As you get closer the PPM goes up. It may not even register until 2" away from a leak. That simple. Instructions are simple and easy to follow. For joints where a leak is detected, usually the next step is to spray or brush on liquid leak detector solution and note the speed and size of the bubbles. Gas companies employees sometime use such a detector, sometime they just use the solution. All you do to uses this is press ON and wait for it to calibrate which lights up the OK LED and beeps. It comes with a really great case. One leak I found was in my mother's basement. We did not smell a thing but I found a pipe joint that was leaking. Since it was on the Gas company piping, they came a fixed it in less than an hour. Later I found other leaks in our relative's houses at joints and at the shutoff valve. This is a really great device to have. It lets you tell the whomever where the leak is so work can be started right away. And realize there can always be more than one leak. The only thing that could be improved is that the two screws that hold the battery case closed are easy to loose since they just fall off when removed instead of being locked to the plastic door. Uses 4 AA batteries.