Hydrofluoric Acid

Hydrofluoric Acid & How To Best Manage First Aid

The Chemical

With the chemical formula HF, Hydrofluoric Acid is Hydrogen Fluoride dissolved in water. It is commercially produced from Calcium Fluoride (CaF₂) and Sulphuric Acid (H₂SO₄). Hydrofluoric Acid is a highly corrosive and colourless acidic solution that should be stored in containers made from polyethylene or fluorocarbon plastic, lead or platinum due to its reactivity with many materials including glass.

Hydrofluoric Acid is a weak acid. This term should not be confused with the terms dilute and concentrated but it relates to how readily the H-F bond dissociates. It is perfectly possible to have a concentrated solution of a weak acid.

Its Use

Hydrofluoric Acid is used to make most fluorine containing materials including Teflon and PTFE as well as refrigerants and pharmaceutical products. Its reactivity makes it ideal to etch or chemically mill metals and it is also widely used in the oil refining industry. The risk of HF exposure must also be considered in any situations where Lithium-Ion batteries are present due to Lithium Hexafluorophosphate electrolytes used.

The Hazards

In addition to being corrosive, HF is also toxic. As with all acids, the H⁺ ion causes the chemical lesions due to reactions with tissue proteins. With higher concentrations of HF these lesions are more marked. The toxicity of the HF derives from the Fluoride ions (F^-). HF also has the ability to penetrate tissue in an undissociated form with the toxic fluoride ions being released later. Fluoride ions have an affinity for Calcium and Magnesium in our body cells and will readily chelate these ions causing a painful local imbalance. The chelated Ca²⁺ and Mg²⁺ then have no action in the usual body equilibrium. Chelation of calcium can result in hypocalcaemia which can lead to cardiac arrhythmias and cardiac arrest. The degree of systemic harm is increased by the concentration of HF - the consequences are more severe at higher concentrations - and the contact time of the chemical with the tissues. Anhydrous Hydrofluoric Acid can have fatal effects when in contact with only 1% of body area, concentrations of less than 20% HF can be lethal when affecting 20% TBSA. Low concentrations of HF (5%) can be lethal in ingestion and inhalation injuries.

First Aid

As always speed is vital when responding to chemical injuries - reducing contact time will help to limit penetration. With HF contact at low concentrations, pain may not be felt immediately so it is important to react quickly to any suspected contamination. The use of appropriate PPE is vital and particular attention should be paid to the selection of the correct material for gloves and for them to be replaced regularly.

Washing with water and application of Calcium Gluconate Gel

The mechanical washing of water will remove chemical from the surface of the skin or eyes. It will also dilute the chemical. This is all in an effort to limit penetration. Calcium Gluconate gel is then applied to the skin to provide a calcium source for the fluoride ions to chelate rather than the calcium within the body cells. In hospital, Calcium Gluconate may be applied by subcutaneous injection, intravenously or by intra-arterial injection for the fingers and hands.

Limitations of this method include the risk of hypothermia due to the volumes of water and washing times required (15 minutes/60l per minute flow rate). The wash-in effect (due to osmotic flow into the skin or eyes) when washing with water can cause further penetration of the chemical. In addition, Calcium Gluconate gel has little effect on the H⁺ions, it requires multiple applications which may cause additional pain on open wounds and there is also the possibility of reversibility of chelation between the calcium provided by the gel and cellular calcium. Calcium Gluconate gel must not be used in the eyes as this can result in corneal calcification.

Decontamination with Hexafluorine®

Hexafluorine® is a washing solution for the skin and the eyes. Its mechanical washing ability is at least as effective as water but has the added benefit of physically acting on both the H⁺ and F^- ions by attracting, binding and rendering them harmless. This active washing ability results in a quicker return to safe physiological tissue pH with less washing solution, reduction in pain due to the chelation of the chemical aggressor and a non-corrosive run off making the first aid safer for casualty and responder.

If used within the first minute Hexafluorine® is able to eradicate the chemical before lesions develop. As a delayed wash - used after the first minute following a splash - Hexafluorine® will limit the progression of the lesion and facilitate the provision of secondary care. Hexafluorine® has an ability to chelate fluoride ions that is 100 times as effective as 2.5% Calcium Gluconate solution injected locally.

For further information download our Hydrofluoric Acid Brochure here: Hydrofluoric Acid

Hydrofluoric Acid