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Hydrogen Chloride Hazards

Hydrogen chloride (HCl), an odorless gas at room temperature, forms white fumes upon contact with atmospheric humidity and, upon contact with water, forms the better-known chemical threat, hydrochloric acid. Even before combining with water, however, gaseous fumes of hydrogen chloride are extremely hazardous to human health, causing a variety of health risks and, in high concentrations, even death.

  1. Respiratory Hazards

    • Hydrogen chloride gas is a powerful irritant of the mucus membranes of the nose, throat and respiratory system, particularly to the upper respiratory tract. Immediate symptoms include rapid breathing, narrowing of the patient's airway and blue coloration of the skin. Concentrations from 50 to 100 parts per million (ppm) can be fatal after an hour, leading to swelling of the throat, throat spasms, accumulation of fluid in the lungs and eventually suffocation. Massive exposure can also lead to reactive airway dysfunction syndrome (RADS), a chemically induced variant of asthma.

    Eyes and Skin

    • Upon contact with humidity on skin or eye tissue, hydrogen chloride gas forms hydrochloric acid, causing intense burning and irritation even at low concentrations. Exposure to the eyes can cause intense pain, ulcers on the surface of the eye and, at higher concentrations, glaucoma, permanent cell damage and cataracts.

    Digestive

    • If ingested, hydrogen chloride can cause pain, nausea and vomiting. At higher concentrations, ingested HCl can cause permanent damage to the digestive tract, inflammation of the mouth, throat, esophagus and stomach and even perforation and life-threatening internal bleeding. Even if the patient receives immediate medical attention, scarring can cause permanent damage to throat and digestive organ capacity. Heavy internal bleeding, moreover, can also cause drops in blood pressure and serious cardiovascular complications.

    Chronic Exposure

    • The United States Occupational Health and Safety Administration (OSHA) sets the safety limit for hydrogen chloride at 5 ppm. Just above those levels, nonetheless, prolonged exposure can cause serious and irreparable damage to human health. Chronic exposure to HCl has been found to cause permanent airway inflammation, discoloration of dental enamel, respiratory ulceration and inflammation of the eyes and skin. Although the deep burning pain caused by HCl at high concentrations makes it relatively easy to detect, few patients can detect HCl in the air at the low and intermediate concentrations that can be very damaging over time.

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