Extended idling is not recomended. But sometimes it is necessary. I've done it myself a few times and I dont like to, but nothing terrible happened.
THE primary concern is of course, vehicle exhaust getting back into the cabin, make sure the rear of the vehicle is 'downwind' so the fumes wont circle around and be returned into the intake vents. You should keep one or two windows slightly open for fresh air. And you should NEVER try to sleep with the engine running.
Next is cooling ability and longevity of the engine. You will need to monitor the temperature gauge if there is one and its not a bad idea to open the hood a couple of inches onto its safety latch to help hot air escape from under the hood.
Extended idling is considered 'severe duty' and like other vehicles that are subject to extended idling, you will need to change the engine oil more often, according to the manufacturer 'severe duty' schedule.
Your vehicle may have an electric radiator fan, if so, make sure it is cycling on and off as needed. If it is a normal mechanical fan mounted on the water pump (or another pulley) just make sure it is moving at least some air when the top of the radiator feels hot. Again, watch that temp gauge!
