You shouldn't leave it running all night in a closed room. The danger of carbon monoxide is why these stoves are designed to automatically turn themselves off after three hours. You can use the timer function to automatically start the stove before you get up in the morning.
In the days before we had these high-tech stoves, people would from time to time open a window or door to ventilate the room. Another practice was to leave a window slightly open, or to leave two windows on opposite sides of the house slightly cracked open to provide a continuous small draft of fresh air through the house.
Unless the room is very small, carbon monoxide probably won't be a danger if you use the automatic three hour shutoff function to stop the stove after you go to bed and then use the timer to restart the stove before you wake up.
If you are using the stove continuously, please be sure to ventilate the room occasionally.