1. One of the basic forms or states of matter. Gas molecules are free and move swiftly in all directions. Their motion and energy are directly proportional to the temperature. A gas not only takes the shape of the containing vessel but expands and fills the vessel no matter what its volume. Among the common important gases are oxygen; nitrogen; hydrogen; helium; sewer gas, which contains carbon monoxide; carbon dioxide; the anesthetic gases; ammonia; and the poisonous war gases. Liquids and solids may release toxic fumes or gases when heated.
SEE: war gas; SEE: anesthesia
2. A colloquial term for an anesthetic.

arterial blood gas

ABBR: ABG Any of the gases present in arterial blood. Operationally and clinically, ABGs include the determination of levels of pH, oxygen (O2), and carbon dioxide (CO2) in the blood. ABGs are important in the diagnosis and treatment of disturbances of acid-base balance, pulmonary disease, electrolyte balance, and oxygen delivery. Values of the gases themselves are usually expressed as the partial pressure of CO2 or O2 although derived values are reported in other units. Several other blood chemistry values are important in managing acid-base disturbances, including the levels of the bicarbonate ion (HCO3), blood pH, sodium, potassium, and chloride.

binary gas

Any gas made of two gaseous components mixed with each other. Some chemical warfare agents are chemically benign when separate but are damaging to living organisms when combined.
SEE: war gas

blood gases

The content of dissolved carbon dioxide and oxygen in plasma. Levels of these gases vary in response to many diseases that affect respiration, e.g., asthma, chronic obstructive lung disease, congestive heart failure, and ketoacidosis.
SEE: acidosis; SEE: alkalosis; SEE: arterial blood gas; SEE: blood gas analysis

Clayton gas

SEE: Clayton gas

coal gas

A flammable, explosive, toxic gas produced from the distillation of coal. It is used for heating and lighting. Its principal constituents are methane, carbon monoxide, and hydrogen.

digestive tract gas

SEE: Intestinal gas.

illuminating gas

A mixture of various combustible gases including hydrogen and carbon monoxide. Its poisonous effects are largely due to carbon monoxide.

inert gas

SEE: Noble gas.

intestinal gas

Any of several gaseous compounds (including carbon dioxide, oxygen, nitrogen, hydrogen, methane, methylmercaptan, and hydrogen sulfide) present in the intestinal tract. They are produced by digestive processes and intestinal bacteria.
SYN: SEE: digestive tract
SEE: digestion; SEE: flatus

laughing gas

An informal term for nitrous oxide.
SEE: nitrous oxide

lewisite gas

SEE: lewisite

lung irritant gas

Any toxic or noxious gas that causes irritation or inflammation of the airways or alveoli.
SEE: war gas

Symptoms of exposure include a burning sensation of the eyes, nose, and throat; bronchitis; and pneumonitis. Pulmonary edema sometimes occurs and may cause severe respiratory failure and death.

Supplemental oxygen and/or mechanical ventilation may be required for hours or days, depending on the extent of lung injury. Aerosolized bronchodilators may also be useful in reducing the work of breathing, and corticosteroids may reduce airway inflammation.

marsh gas

SEE: Methane.

mustard gas

Dichlorethyl sulfide, a poisonous gas used in warfare.
SEE: vesicant gas; SEE: war gas

nerve gas

Any of several gaseous materials used in chemical warfare. The agents may be stored in liquid form but are aerosolized at the time of use. These chemicals are readily absorbed through the skin. Some forms, i.e., organophosphates that inhibit acetylcholinesterase, cause copious secretions from the nose, eyes, mouth, lungs, and intestines. Muscle fasiculations, twitching, and miosis will result from exposure. A large dose may cause sudden unconsciousness, convulsions, flaccid paralysis, apnea, and death. With some agents, only a few breaths of the vapor may cause death.

Charcoal-lined suits offer barrier protection. The agents will penetrate ordinary clothing worn with a gas mask.

Pretreatment with pyridostigmine and concurrent treatment at the time of exposure with atropine, pralidoxime, and diazepam may be life-saving. Artificial respiration is mandatory. The skin should be decontaminated with household bleach diluted with water at a ratio of 1:10, or with soap and water, and the eyes should be irrigated with plain water. Military personnel carry small towels impregnated with chloramine, hydroxide, and phenol.

Descriptive text is not available for this imageGas masks should cover face and eyes and be proven to be adequately effective. People treating patients must protect themselves from contact with toxic chemicals on clothing, hair, and skin.

SEE: war gas

nitric oxide gas

A toxic gas administered in very small concentrations during mechanical ventilation to treat persistent pulmonary hypertension.
SEE: nitric oxide

noble gas

Any of the six colorless, odorless, minimally chemically reactive gaseous elements found in group 18 of the periodic table. The gases are argon, helium, krypton, neon, radon, and xenon.
SYN: SEE: inert gas

nose irritant gas

C12H10AsCl (diphenylchloroarsine), an odorless, toxic smoke. It causes intense pain in the nose, throat, and air passages, sneezing followed by headache and aching in the teeth and jaws, acute mental depression, and sometimes vomiting. Nasal douching with warm sodium bicarbonate solution is helpful.
CAS # 712-48-1

SEE: war gas

refrigerant gas

Any of several gases, e.g., Freon, used in ordinary household refrigerators. Poisoning may be caused by leaks, faulty connections or breakage, or gas dissipated into the atmosphere.

sewer gas

A gas that is produced by decaying matter in sewage and contains methane and hydrogen sulfide. It is toxic, usually flammable, explosive, and may be used for fuel.

suffocating gas

Any of several war gases, such as phosgene or diphosgene, made from chlorine compounds that irritate or injure the airways.
SEE: lung irritant gas; SEE: war gas

tear gas

SEE: riot control agent

vesicant gas

A type of gas that blisters the skin. Clothing and boots become contaminated and a source of danger. Mustard and lewisite gases are examples.

Symptoms do not appear immediately but may be delayed 6 hr or longer. Eye pain, lacrimation, and discharge may be the first evidence. The eyelids swell, and the patient becomes unable to see. A diffuse redness of the skin is followed by blistering and ulceration.

Decontamination is essential and must be thorough. The eyes should be bathed freely with normal saline or plain water. No bandage should be worn. The patient should be scrubbed, if possible, under a hot or warm shower for 10 min. If blisters arise despite these precautionary measures, they should be treated with a mild antiseptic and a protective dressing.

vomiting gas

A gas, particularly chloropicrin, that induces vomiting.

war gas

Any chemical substance, whether solid, liquid, or vapor, used to produce poisonous gas with irritant effects. The agents can be classified as lacrimators, sternutators (sneeze-causing), lung irritants, vesicants, and systemic poisons, such as nerve gas. Some gases have multiple effects.
War gases are known as nonpersistent (diffusing and dispersing fairly rapidly) or persistent (lingering and evaporating slowly).

When giving first aid, the rescuer avoids becoming a casualty by taking appropriate precautions. All gas masks are checked to ensure that they are in working order. The rescuer first puts on his or her own mask, then fits masks to patients. The rescuer's skin is covered, and exposed skin of persons at risk is flooded with water to flush off suspected chemical contaminants.

Decontamination centers are essential to the rescue effort. Thorough decontamination of patients, clothing, foot coverings, equipment, and even ambulances precedes admitting patients to emergency care areas to prevent unaffected people in the area from becoming casualties. Pulmonary and neurological functions are closely monitored, and specific or supportive therapies instituted as necessary.