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14 January 2021

Hydrofluoric Acid and Fluorides. How can you limit your exposure ?

Hydrofluoric acid (HF) is a chemical that is deadly when inhaled and when in contact with the skin. First aid, accidental spills, decontamination of equipment – Find out our advice for managing this acid in order to limit the exposure of your employees.
accidental chemical spill: a person wearing a protective suit prepares to use a neutralizing absorbent

What is hydrofluoric acid, and what are the dangers ?

Hydrofluoric acid is a corrosive chemical whose formula is HF. It is volatile, colourless and has an acrid odour. Anhydrous, it is gaseous at ambient temperatures and may be dissolved in water up to a concentration of 75%. In an aqueous solution, hydrofluoric acid dissociates, meaning that it forms ions of H+ acids and F ions called fluorides.

According to the harmonised classification of chemicals, hydrofluoric acid is classified as fatal in contact with skin (H310), fatal if swallowed (H300), fatal if inhaled (H330) and causes severe skin burns and eye damage (H314).

Diluted solutions of hydrofluoric acid are also classified as hazardous when concentrations are higher than 0.1%. Solutions of hydrofluoric acids corrode most metals and release dihydrogen, a gas that is flammable and explosive.

A few common uses

example of a semiconductor made with hydrofluoric acid
Industrial use :

Hydrofluoric acid is capable of dissolving silica, which is why it’s used in many operations for etching, cutting glass, in refining, or in semi-conductor manufacturing.
person cleaning car rims with hydrofluoric acid-based product
Use by individuals :

Low concentrations are also found in everyday products used in mechanics, in particular in the form of stripping pastes used after welding work, to clean car rims, pickling operations, etc.

How does hydrofluoric acid affect the organism ?

diagram showing the effects of hydrochloric acid on the organism in contact with it: corrosion
It’s the dual presence of H+ et F– in the same environment that is responsible for the significant hazard posed by hydrofluoric acid. First, HF has a local effect when in contact with the organism. Once H+ enters into contact with the skin, it destroys the superficial layers and creates lesions through its corrosive effect. As for the fluoride ions F–, they do not easily penetrate through the upper layers of the skin. However, if the superficial layers have been damaged by an acid injury or a microcut, the F– ions will penetrate more deeply and destroy the tissues through cellular necrosis.
diagram showing the effects of an incision followed by fluoride ion application: necrosis
Hydrofluoric acid also has an effect on the system, meaning that it affects the entire organism, not just the area of the body where the projections have occurred. Following penetration, the fluoride ion combines with the magnesium and the calcium in tissues or bones and deprives the organism of them. The lack of calcium in the organism, called hypocalcaemia, can lead to death through heart dysfunction even in the case that a small surface of the body (e.g., an arm) comes into contact with HF.
hand chemical burn
Figure 1 : example of a hydrofluoric acid chemical lesion on an index finger. The white spots noticed are calcium fluoride CaF2, a molecule formed when fluoride ions combine with the calcium in the organism.
One of the particularities of hydrofluoric acid that makes it so dangerous is that symptoms are delayed, which leads to a delay in treatment. When diluted HF solutions are used, the action of the H+ ions is slower, with the pain and symptoms appearing only after several minutes or even hours after contact.

→ This is why it is very important to protect oneself from all contact with hydrofluoric acid or its derivatives even if the concentrations or volumes used are low.

How can you limit your employees’ exposure ?

sign to warn employees of chemical risks: "personal protective equipment must be worn"

Beforehand :

  • Limit your stock of HF, use a substitute when possible and check that it cannot come into contact with incompatible chemicals (water, strong bases, etc.)
  • Check whether the materials used are compatible with HF.
  • Use collective protective equipment (chemical hoods, closed circuits, etc.) and wear mandatory, appropriate personal protective equipment
  • Train personnel on the chemical hazards related to hydrofluoric acid.
5L sprayer of Safurex® chemical decontaminant

On a daily basis or during maintenance :

To limit employee exposure to hydrofluoric acid or its derivatives, chemical decontamination and cleaning is advised for all surfaces where projections or drops of HF may have landed: lab tables, PPE, rims once treated, workstations, etc.

SAFUREX®, the chemical decontaminant, was created for decontaminating equipment that comes into contact with HF and fluorides. It neutralises the acid nature of the H+ ions by bringing the pH to a neutral pH, but also fixes the F fluoride ions.

Once they’ve been fixed by SAFUREX®, the fluoride ions are no longer able to combine with the calcium or magnesium in the organism and are thus rendered harmless.

First Aid – Managing an accident :

In the event of hydrofluoric acid chemical projections, our recommendation is to decontaminate the victim as quickly as possible, using Hexafluorine® solution. Find out more on this first aid solution at Hexafluorine® solution

Calcium gluconate is often prescribed to provide a source of calcium to the organism and offset the effect of the fluorides.

a person wearing a safety suit sprays hexafluorine on a victim of a chemical spraying accident

In the event of spills :

two employees in protective suits use a neutralizing absorbent during a major acid spill - chemical hazard
When there’s a hydrofluoric acid leak, it’s important to use products that are compatible with HF. Traditional absorbents like diatoms or sepiolites are composed of silica, and will therefore melt in contact with HF, cause the mixture to heat and make the situation worse.
The use of neutralising absorbents compatible with hydrofluoric acids, such as TRIVOREX® or ACICAPTAL®, allow spills to be neutralised safely. The acid nature of HF will be eliminated, emissions of acid vapours halted, thus minimising the hazard.
After handling the leak, it is important to decontaminate all equipment and PPE which have been contaminated by HF to avoid further contamination of staff.

To find out more :