Symptoms depend on which gas or chemical is inhaled and how deeply and for how long it was inhaled.
Symptoms may include irritation of the eyes or nose, cough, blood in the sputum, and shortness of breath.
Chest x-rays, computed tomography, and breathing tests are used to determine how much lung damage has occurred.
Oxygen and drugs to open the airways and decrease inflammation are given.
(See also Overview of Environmental Lung Diseases Overview of Environmental Lung Diseases Environmental lung diseases are caused by harmful particles, mists, vapors, or gases that are inhaled, usually while people work. If the lung disease is due to inhaled particles, the term pneumoconiosis... read more .)
Many types of gases—such as chlorine, phosgene, sulfur dioxide, hydrogen sulfide, nitrogen dioxide, and ammonia—may suddenly be released during industrial accidents and may severely irritate the lungs. Gases have also been used as chemical warfare agents Overview of Chemical-Warfare Agents Chemical weapons are developed by governments for wartime use and include Toxic agents (intended to cause serious injury or death) Incapacitating agents (intended to cause only temporary, non–life-threatening... read more .
Gases such as chlorine and ammonia easily dissolve and immediately irritate the mouth, nose, and throat. The parts deep inside the lungs are affected only when the gas is inhaled deeply. A common household exposure occurs when a person mixes household ammonia with cleansers containing bleach. The irritant gas chloramine is released.
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Some gases—for instance, nitrogen dioxide—do not dissolve easily. Therefore, they do not produce early warning signs of exposure, such as irritation of the nose and eyes, and they are more likely to be inhaled deeply into the lungs. Such gases can cause inflammation of the small airways (bronchiolitis) or lead to fluid accumulation in the lungs (pulmonary edema).
Silo filler’s disease (which mostly affects farmers) results from inhaling fumes that contain nitrogen dioxide given off by moist silage, such as fresh corn or grains. Fluid may develop in the lungs as late as 12 hours after exposure. The condition may temporarily resolve and then recur 10 to 14 days later, even without further contact with the gas. A recurrence tends to affect the small airways (bronchioles).
Inhalation of some gases and chemicals may also trigger an allergic response that leads to inflammation and, in some cases, scarring in and around the tiny air sacs (alveoli) and bronchioles of the lung. This condition is called hypersensitivity pneumonitis Hypersensitivity Pneumonitis Hypersensitivity pneumonitis is a type of inflammation in and around the tiny air sacs (alveoli) and smallest airways (bronchioles) of the lung caused by a hypersensitivity reaction to inhaled... read more .
Radioactive gases, which may be released in a nuclear reactor accident, may cause lung cancer Lung Cancer Lung cancer is the leading cause of cancer death in both men and women. About 85% of cases are related to cigarette smoking. One common symptom is a persistent cough or a change in the character... read more 
and other cancers many years after the exposure.
Other inhaled gases may cause a general body poisoning (including breathing difficulty) because they are poisonous to the body's cells (such as cyanide) or because they displace oxygen in the blood and therefore limit the amount of oxygen reaching the tissues (such as methane or carbon monoxide).
In some people, inhalation of small amounts of gas or other chemicals over a long period may result in chronic bronchitis (inflammation of the airways). Also, inhalation of some chemicals, such as arsenic compounds and hydrocarbons Hydrocarbon Poisoning Hydrocarbons are petroleum products, such as gasoline and kerosene, and are also ingredients in many paint thinners, solvents, glues, and some cleaning products. They are dangerous when the... read more 
, can cause cancer. Cancer may develop in the lungs or elsewhere in the body, depending on the substance inhaled.
Symptoms of Gas and Chemical Exposure
Soluble gases such as chlorine, ammonia, and hydrofluoric acid cause severe burning in the eyes, nose, throat, windpipe, and large airways within minutes of exposure to them. In addition, they often cause cough and blood in the sputum (hemoptysis). Retching and shortness of breath also are common.
Less soluble gases such as nitrogen dioxide and ozone cause shortness of breath, which may be severe, after a delay of 3 to 4 hours and sometimes up to 12 hours after exposure (see also Air Pollution–Related Illness Air Pollution–Related Illness Illnesses related to air pollution are considered environmental lung diseases. (See also Overview of Environmental Lung Diseases.) The major components of air pollution in developed countries... read more ). With less soluble gases, long-term lung damage can occur and cause chronic wheezing and shortness of breath.
Diagnosis of Gas and Chemical Exposure
A history of relevant exposure
Chest x-ray or computed tomography (CT)
A chest x-ray can show whether pulmonary edema or bronchiolitis has developed. Computed tomography is especially helpful when people have symptoms but their chest x-ray looks normal.
A sensor is attached to the person's finger to determine the amount of oxygen in the blood (pulse oximetry).
Tests of lung function, including determining how much air the lungs can hold and the rate at which oxygen and carbon dioxide are exchanged, are done to evaluate lung damage.
Prognosis of Gas and Chemical Exposure
Most people recover completely from accidental exposure to gases. The most serious complications are lung infection or severe damage that causes scarring of the small airways (bronchiolitis obliterans). Some studies have shown long-term impairment of the lung function years after episodes of exposure to gases.
Prevention of Gas and Chemical Exposure
The best way to prevent exposure is to use extreme care when handling gases and chemicals. People using cleaning products or other chemicals at home should work in well-ventilated areas.
Gas masks with their own air supply should be available in case of accidental spillage. Farmers need to know that accidental exposure to toxic gases in silos is dangerous, even fatal. People should not enter an environment where poisonous gases may be present to rescue an exposed person unless they have protective gear.
Treatment of Gas and Chemical Exposure
Oxygen therapy
Oxygen is the mainstay of treatment for people who are exposed to gases. If lung damage is severe, a person may need mechanical ventilation Mechanical Ventilation Mechanical ventilation is use of a machine to aid the movement of air into and out of the lungs. Some people with respiratory failure need a mechanical ventilator (a machine that helps air get... read more . But any person who has breathing problems after inhaling a gas is usually monitored in a hospital overnight to ensure that serious complications do not occur. Drugs that open the airways (bronchodilators), intravenous fluids, and antibiotics may be helpful. Corticosteroids such as prednisone are often given to reduce inflammation in the lungs.
