New to pulling a fifth wheel

Most of the rest areas on the east coast have these kind of signs, limiting idle time. Once had a highway patrol cruising the lot, knocking on doors, up in New Hampshire. I had just pulled in, was doing my log book when he drove up to my door. He reminded me that there was a twenty minute idle limit for trucks. It was something like 15 degrees, my little home was a fiberglass shell. I told him I was out of hours (illegal to drive) and to go home and tell his wife and kids they couldn't run their furnance, then I would shut off mine. I never saw him again, my truck ran all night.