It’s a direct-vent space heater. I dated a girl that had an apartment heated the same way. Both bedrooms faced the living room so she and her roommate slept with their doors open in winter and a fan in each doorway blowing out (figuring the air at the floor was colder so it should blow toward the heater…no idea if it helped).

They heated (and humidified!) the kitchen with a giant lobster pot full of water over a burner on low. Good times.