at least keep the window partially opened while leaving your heater on.
lastly, the cleaning and maintenance work are critical so as to keep your heater in a good shape. regularly clean off the dust from your heater’s fan and surface. check for any product defects and malfunction. you can contact a professional for help.
my heater guide is end. in conclusion, to choose the best portable heater, you just know which type you want, its particular features to choose and how to do maintenance work. 