Emphatically YES. Despite the scare stories that seem to do the rounds, I am yet to hear of a single person having an issue with the safety of these heaters.
Firstly the fuel is diesel which is not highly combustible – unlike petrol. Secondly – the combustion takes place in a sealed chamber so it doesn’t use a flame anywhere.
That said anything can be dangerous if not used with common sense.
But if you are concerned about your caravan catching fire from the heater itself then you can rest easy. There is more chance of a ‘fire’ from an electrical short than from the unit itself.