Each chemical may be in different physical forms. Generally we deal with solids, liquids, or gases. Solids - are materials that hold their own shape and are normally hard or structurally firm. Solids may be too small to see and be inhaled deeply into the lungs. May float in the air.
Respiratory system is well equipped with nose hair and cilia to bring dusts back out of the system.
Produced when metals are heated to high temperatures and are atomized. They then oxidize in the air and become extremely fine metallic particles which are not handled well by the respiratory system. Metal fume fever is a common disorder in the welding profession. Smoke is extremely variable in particle size and toxicity. Health effect depends on hazardous decomposition products and the temperature of the burning materials.