Is it permissible to leave a diesel heater burning overnight while sleeping in cases of extreme cold or otherwise?

It is not permissible to leave a heater on while sleeping or unsupervised in the house if there is a fear of harm from it, due to the Prophet's (peace be upon him) saying: "Indeed, this fire is an enemy to you, so when you sleep, extinguish it." However, if there is no fear of harm, then there is no objection, because a ruling revolves around its cause, in existence and non-existence.