It depends. Coal, charcoal, wood. The house where my father grew up vented smoke/exhaust from the fires in the kitchen under a hard clay bed built into the house to keep the family warm in the winter.
You can see the effect of years of exposure to soot on the faces of people who live in rural China (and, I daresay, anyone who lives in similar circumstances). These people are not living particularly environmentally clean lives right now (although, to be fair, they probably do consume far fewer manufactured goods than their city-dwelling brethren).
Something of interest is the prevalence of solar water heaters, both in urban and rural areas. They are surprisingly common, much better than heating water using fire or electricity, and affordable even to those outside the cities.
You can see the effect of years of exposure to soot on the faces of people who live in rural China (and, I daresay, anyone who lives in similar circumstances). These people are not living particularly environmentally clean lives right now (although, to be fair, they probably do consume far fewer manufactured goods than their city-dwelling brethren).
Something of interest is the prevalence of solar water heaters, both in urban and rural areas. They are surprisingly common, much better than heating water using fire or electricity, and affordable even to those outside the cities.