16. (1995):

Hydrogen fluoride is extremely corrosive. It is a fuming, colourless liquid at normal atmospheric pressure and less than 19^oC. Above 19^oC, hydrogen fluoride is a gas. Hydrogen fluoride is industrially available as a liquid under pressure (anhydrous hydrofluoric acid) or more commonly, as an aqueous solution (aqueous hydrofluoric acid (HF)), with a concentration in the range of 30 - 70 % HF w/v[1]. The most common concentration for analytical grade HF is 48 % HF w/v[2].

Hydrofluoric acid is commonly used for digesting minerals, etching glass, and as a fluorinating agent, metal pickling, and more.

Hydrofluoric acid exposure[3] may be -

Acute (short term) -

• Spillage on the skin, or splash in the eyes. This causes; intense pain, either immediately or after some hours, a tough white coagulation over the burnt area (a slow healing ulcer), and progressive destruction of tissue including decalcification and necrosis of bone. A 2 % (approximately 360 cm²) body burn from 70 % hydrofluoric acid may cause death.

The eyes are especially sensitive.
• Inhalation of gas or mists, leading to asphyxia from pulmonary oedema (fluid in the lungs) and convulsions.
• Ingestion, burning of mouth and pharynx, nausea, vomiting, abdominal pain.

• Skin ulcers,
• Bone and teeth damage,
• Irritation of nose, throat and bronchi.

A recent incident[4] demonstrates just how dangerous hydrofluoric acid can be -

Whilst sitting at a fume cupboard processing mineral samples, a laboratory technician knocked approximately 100 mL of hydrofluoric acid onto his thighs. Immediate 10 % body burns ensued, despite rapid flushing with water and emergency hospitalisation. The following week his leg was amputated, however, the individual eventually succumbed to the toxic effects of the HF. He died 15 days after the accident.

Several factors contributed to the accident -

• Failure to protect the skin from exposure with appropriate clothing.
• Failure to restrain containers of HF in secure holders.
• Failure to apply neutralising cream.
• Lack of emergency planning/facilities/personnel.
• Poor work station design.

• Ensure that personnel are familiar with the properties and hazards of dangerous chemicals.
• Follow appropriate safe work practices.
• Plan work in the knowledge that any exposure may cause permanent incapacity or death.
• Where practicable substitute with a less dangerous substance.
• Use minimum quantities.
• Train workers in safe procedures, personal protection and first aid/emergency procedures in accordance with the worksafe Guide on Hydrogen Fluoride 1989 [5].
• Ensure appropriate personal protective equipment is used. This shall include: a face shield (or safety glasses); a PVC apron; natural, butyl rubber or PVC gloves.

Note: these gloves materials all degrade in the presence of HF - inspect and replace before they break.
• Ensure that safety showers, eye wash facilities and calcium gluconate gel are available wherever HF is used.
• All work should be conducted in a fume cupboard.
• Person should not work alone with HF.

• Contaminated clothing should be washed with bicarbonate of soda solution.
• Contaminated equipment should be neutralised with calcium hydroxide, before being washed with water.
• Containers should be stored away from heat and in well ventilated areas. Ideally it should stored in a secondary container.
• Special acid gas respirators are required to treat spills, outside a fume cupboard.

FIRST AID PROCEDURES

SKIN

• Remove contaminated clothing and deluge the burnt areas with water.
• Seek emergency medical treatment.
• Apply calcium gluconate gel on and around the burn. Massage it in with clean fingers (preferably gloved), until 15 minutes after the pain has subsided. This may require several hours, but continue massaging with the gel so long as there is improvement in the symptoms.
• Where a thick necrotic coagulum (dead tissue mass) has formed, this should be removed and the gel then massaged into the base of the burn, taking aseptic precautions.
• If the burn fails to respond to the gel, injection of a 10 % calcium gluconate into and under the burn should be considered. The quantity injected will be governed by the relief of pain.
• Local anaesthesia is contra-indicated, so that the splitting of finger and toe nails should be performed under general anaesthesia.
• The burns may not require dressing, but where they do, use the calcium gluconate gel.
• Advise the patient to return for further treatment if the pain recurs.
• Treat symptomatically.

• Irrigate with copious quantities of isotonic saline or water.
• Seek emergency medical treatment.
• Instil sterile calcium gluconate drops, 10%.
• Treat symptomatically.

• Remove to fresh air.
• Artificial respiration and oxygen is necessary.
• Remove to hospital by ambulance accompanied by the Material Safety Data Sheet.
• Continue observation for 48 hours because of the dangers of pulmonary oedema.

• Give copious quantities of lime water, milk or water drinks (in spite of vomiting).
• Remove to hospital by ambulance accompanied by the Material Safety Data Sheet.
• Intravenous injection of 10 mL of 10% calcium gluconate repeated hourly and given slowly.

In large burns of over 160 cm², or in cases of ingestion and severe inhalation, calcium and/or magnesium may be severely reduced in the blood serum.

Give calcium and ascorbic acid in water by mouth every two hours until admitted to hospital. Frequent electrolyte monitoring will decide future conduct in the case.

References:

Patty's Industrial Hygiene and Toxicology, Volume 2B: Toxicology, 3rd edition, 1981, John Willey & Sons, USA.

BDH Laboratory Supplies 1994/95, Merck Pty Ltd.

Environmental & Industrial Health Hazards, a Practical Guide, R.A. Trevethick, 2nd edition, 1980, William Heinemann Medical Books Ltd, London.

Significant Incident Summary, Department of Occupational Health, Safety and Welfare, WA.

Worksafe Australia Guide, Hydrogen Fluoride, 1989.