Hydrogen fluoride (Hydrofluoric acid)

Hydrogen fluoride was first obtained in 1771 by Carl Wilhelm Scheele and became industrially important in the early 20th century as the key reagent for aluminum production — HF is used to make cryolite (sodium aluminum fluoride), the electrolyte used in aluminum smelting [1]. Today HF is produced at approximately 500,000 tons annually worldwide for multiple applications: aluminum production, nuclear fuel processing (uranium hexafluoride), petroleum alkylation (making high-octane gasoline), semiconductor etching and cleaning, and stainless steel pickling [2]. In petroleum refining, HF is used in catalytic alkylation units — large-scale HF facilities at refineries in densely populated areas have been a source of concern following accidents and near-misses. Several industrial accidents have released HF clouds that injured or killed workers and caused community evacuations [3].

Occupational exposure is the dominant pathway for significant HF exposure — workers in semiconductor manufacturing, petroleum refining, aluminum production, nuclear fuel processing, and metal surface treatment all have potential HF contact [1]. Consumer products containing HF include some rust removers, wheel cleaning products, and certain home cleaning agents — these typically contain dilute hydrofluoric acid at concentrations of 1–12% [2]. These consumer products are responsible for many accidental burns. Community exposure from industrial accidents near HF-using facilities is a recognized emergency response concern. Fluoride in drinking water (as fluorosilicic acid, added for dental health) is a chemically different form than HF [3].

HF is uniquely dangerous because it is a weak acid that does not immediately cause the burning pain of strong acids, allowing deep penetration before the extent of injury is apparent [1]. Fluoride ions penetrate through skin and tissue, chelating calcium and magnesium in cells — depleting these essential minerals from serum and tissue. The result is hypocalcemia (dangerously low calcium) and hypomagnesemia, which cause life-threatening cardiac arrhythmias. Patients have died from cardiac arrest following small HF skin exposures (as little as 2.5% of body surface area with concentrated HF) [2]. Full-thickness skin burns, deep tissue destruction, and bone damage occur even from dilute solutions. Inhalation of HF vapor causes severe pulmonary edema and death at relatively low concentrations [3].

Semiconductor industry workers who etch silicon wafers with HF solutions face significant occupational exposure risks [1]. Petroleum refinery workers at alkylation units using HF catalysts have both routine and accident-related exposure risks. Aluminum smelter workers, metal surface treatment workers, and nuclear fuel processing workers have occupational exposure [2]. Consumers who use rust removers, wheel cleaners, or other consumer products containing HF risk accidental burns — particularly dangerous because the lack of immediate pain leads to underestimation of the exposure.

For consumer products: avoid rust removers, wheel cleaners, and stone etching products that contain hydrofluoric or fluoric acid — read labels carefully and choose alternative products [1]. If HF contact is suspected despite precautions, immediate first aid is calcium gluconate gel applied to the exposed area and immediate emergency care — call 911 and explain it is an HF exposure, not an ordinary acid burn [2]. Occupational workers must have calcium gluconate gel readily available at all HF work areas for immediate first aid. Wear impermeable gloves (nitrile or neoprene — not latex, which is permeable to HF), face shields, and chemical-resistant clothing. Never work with HF alone — a buddy system is required because rapid incapacitation can occur [3]. Ensure your workplace's emergency shower and eyewash stations are immediately accessible from HF work areas.