What is the characteristic smell of Class A fires?

Class A fires typically involve ordinary combustible materials such as wood, paper, textiles, and some plastics. The characteristic smell associated with Class A fires is due to the combustion of these materials, resulting in gray or brown smoke that has a distinctly ashy odor. This smell arises from the burning of organic substances, which emit various volatile compounds during combustion, including those that contribute to an ashy scent. Thus, when identifying a Class A fire, one would recognize the presence of this particular smell, serving as an indicator of the materials involved in the fire.