Is it safe to have 10 month old sleeping with air conditioner on overnight on a very hot summer night? And with the door closed?

Red Nose recommends that you dress baby according to the room temperature & that it is not necessary to keep cooling/heating on all night.
However, if you use heating/cooling check that baby is not too warm or too cold - keep temperature regulated & baby dressed accordingly.
https://rednose.org.au/article/how-to-dress-baby-for-sleep