Smoke inhalation

[Justin Bieber]

Smoke can suffocate people and sometimes also contains toxic chemicals produced by the burning substance. Some of these chemicals can damage the lungs or poison the body.
Many people who have been burned in fires have also inhaled smoke. Sometimes people inhale smoke without sustaining skin burns.
Inhaling small amounts of smoke usually causes no serious, lasting effects. However, if the smoke contains certain poisonous chemicals or is unusually dense or if inhalation is prolonged, serious problems can develop. Even common household materials such as plastics and fabrics can produce poisonous chemicals (toxic products of combustion) when they burn.
Smoke inhalation can cause problems in several ways:

Suffocating the body with carbon monoxide
Poisoning the body with toxic chemicals
Damaging the windpipe, breathing passages, and/or lungs from toxic chemicals
Burning the mouth and throat from hot gases

Carbon monoxide is a gas produced in many fires. When inhaled, carbon monoxide prevents the blood from carrying oxygen so tissues do not get enough oxygen (see also Carbon Monoxide Poisoning).
Many household and industrial substances release cyanide when burned and cause cyanide poisoning.
Inhalation of chemicals released in the smoke, such as hydrogen chloride, phosgene, sulfur dioxide, toxic aldehyde chemicals, and ammonia, can cause swelling and damage to the windpipe (trachea) and even the lungs. Eventually, the small airways leading to the lungs narrow, further obstructing airflow.
Hot smoke usually burns only the mouth and throat rather than the lungs because smoke cools quickly. However, an exception is steam, which carries much more heat energy than smoke and thus can also burn the airways in the lungs.

[Julian]

When smoke is inhaled, toxic products of combustion injure airway tissues and/or cause metabolic effects. Hot smoke usually burns only the pharynx because the incoming gas cools quickly. An exception is steam, which carries much more heat energy than smoke and thus can also burn the lower airways (below the glottis). Many toxic chemicals produced in routine house fires (eg, hydrogen chloride, phosgene, sulfur dioxide, toxic aldehydes, ammonia) cause chemical burns. Some toxic products of combustion, such as carbon monoxide or cyanide, impair cellular respiration systemically.
Burns and smoke inhalation often occur together but may occur separately.
Upper airway injury usually causes symptoms within minutes but occasionally over several hours; upper airway edema may cause stridor. Significant orofacial burns can cause edema that significantly compounds the upper airway problems created by smoke inhalation.
Lower airway injury may also occur with upper airway injury and usually causes delayed symptoms (eg, oxygenation problems highlighted by increasing oxygen requirements or decreases in lung compliance 24 h or later).
Symptoms of smoke inhalation include

Local irritant phenomena: Cough, wheezing, stridor
Hypoxic manifestations: Confusion, lethargy, coma
Carbon monoxide poisoning: Headache, nausea, weakness, confusion, coma