Smoke is poisonous. The products of burning include the gases carbon monoxide, carbon dioxide and water vapour. Carbon monoxide and carbon dioxide are poisonous gases. Other products of the fire are irritating, causing coughing or streaming eyes. Smoke is difficult to see through.
Smoke contains particle of unburnt carbon that make it look black.
Soot particles make it hard to see through smoke. These products arise as a result of inefficient combustion. Smoke is hot. Hot gases rise because they are lighter then air. Because smoke is usually much hotter than the surrounding air it tends to rise.