When you breathe in a gulp of air, it travels down your windpipe (or trachea). Rings of cartilage keep the windpipe from collapsing so that the air can easily move through the windpipe, past your collarbone, your ribs, and to the center of your chest.
There, your windpipe divides into two tubes called the bronchial tubes, each of which leads to one of your lungs. By the time your gulp of air reaches the lungs, most dirt particles, smog, dust, and bacteria have already been swept away by the hairs in your nose, by a strong sneeze, or a sudden cough.
But just in case that's not enough, the lungs themselves have protective devices to keep poisons such as smoke, dust, and other the everyday pollutants at bay.
The bronchial tubes break down into millions of tiny tubes, called bronchioles. Within these bronchioles are little pockets called alveoli (which almost rhymes with ravioli). These alveoli (the plural of the singular alveolus), which are surrounded by capillaries, are only a membrane away from the blood cells that are clambering for the oxygen “food” you've just inhaled. The alveoli are the moat around the castle—the fortress wall that keeps enemies at bay.
Because it's important that the oxygen not be tainted, the human's genetic makeup contains a kind of vacuum cleaner to catch wayward dust. The alveoli are covered with wet and sticky mucous. Dust particles (which have also broken down into minute cells) stick to these mucous walls.
Now comes the cleaning-up part. The alveoli also contain mucous cells with membrane “arms” called cilia. Cilia resemble sweeping, swaying tentacles. The dust catches on the cilia and is swayed back, out of the lung, into the part of the throat (the esophagus) that leads to the stomach. Acids in the stomach area begin to make short shrift of the “poison.” Your body cells receive the clean oxygen and eliminate carbon dioxide waste that is exhaled out of your lungs.
Although minor incidents are not medical emergencies, they can turn into emergencies if the person involved has asthma, allergic bronchitis, emphysema, or any other chronic pulmonary disease. These people are more sensitive to smoke, and what is minor in a normal person can wreak havoc in a sensitive one. Even smoke from an ordinary campfire can cause a severe asthma attack! A good rule of thumb is to seek medical attention for any asthmatic who is wheezing, no matter how minor the inhalation seems. This especially holds true for young children!
Unfortunately, when you become overcome with smoke, this process of “cleaning,” receiving, and eliminating breaks down. There are just too many foreign particles for the cilia to sweep them all away. Even the automatic “defense mechanisms” of sneezing and coughing will not help clear your lungs of smoke. They are merely a drop in the bucket.
When you suffer from smoke inhalation, your body does not get the oxygen it needs to do its job—and the lungs can become damaged as well.