The emissions from firewood- and pellet-burning heaters contain mainly o-hydroxyphenol, 4-methoxyphenol, and Ph. In the emissions from gasoline-powered vehicles, only Ph was detected, and in those of diesel-powered vehicles, only 2-NPh and 4-NPh were detected. Kerosene-burning heaters did not exhibit measurable amounts of phenolic compounds in their emissions. The controlled irradiation of the emissions from the burning of firewood and pellets using a photochemical camera showed high degrees of stability of these compounds. The studied phenolic derivatives did not photolyse or were not formed by the photochemical pathway; therefore, their origin is clearly primary, which allows their use as combustion tracers in a particular atmosphere. The presence of Ph derivatives in the Santiago atmosphere indicates the existence of mobile sources (daytime) and the use of firewood (night-time). The presence of 2-NPh and 4-NPh derivatives in the air would be strongly associated with the use of mobile sources that use diesel. In contrast, catechol is associated with the burning of wood for heating.