Hydrofluoric Acid, HF

16. (1995/2003)

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, metal pickling, and as a fluorinating agent.

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.  Hydrofluoric acid penetrates rapidly and deeply below fat layers binding and depleting tissue calcium.  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.

Chronic (long term) -

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

Chronic poisoning is not common.

A 1994 incident [4] demonstrated 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.

It is a requirement that Research Groups using HF (check these against your work place) -

• Ensure that personnel are familiar with the properties and hazards of dangerous chemicals.
• Conduct and document a Risk Assessment for its intended use.  Work with HF is considered a Risk Category C1 or C2 (depending on acid concentration) under the ANU Risk Management for Chemicals guidelines (http://info.anu.edu.au/policies/_DHR/Procedures/Risk_Management_for_Chemicals.asp ).
• Where practicable, substitute with a less dangerous substance.
• Follow appropriate documented safe work practices.
• Train workers in safe procedures, personal protection and first aid/emergency procedures.  The National Occupational Health and Safety Commission Guide on Hydrogen Fluoride 1989 [5] may be of assistance or the ANU Corrosive Substances Safety course (/Training_and_Development/OHS_Training/Advanced_Courses/index.asp).
• Plan work in the knowledge that any exposure may cause permanent incapacity or death.
• Buy and Use minimum quantities.  The maximum container to be purchased should not exceed 500 mL, to minimise decanting risks.
• 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, and sleeve protectors.
  Note: these gloves materials all eventually 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.
• A person should not work alone with HF, or during periods when normal assistance services (eg. first aid, emergency wardens etc) are not available (ie. after-hours or on weekends).

Additional information -

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

Additional information is available from the OHS Unit.

First Aid Kit

A hydrofluoric acid first aid kit must be available at the workplace where HF is used.  A typical kit must contain at least –

• 3 pairs of disposable gloves (eg. latex surgical gloves)
• Calcium Gluconate Gel (has a limited shelf life ~ 1 yr)
• Saline solution (sodium chloride) (Steri Tube, Eyesaline® solution or equivalent) ~ 300 mL
• Eye pads
• Bandages

(ANU) Hydrofluoric Acid First Aid Kits and Calcium Gluconate Gel are available from PARASOL EMT Pty Ltd.

Spill Management

Where hydrofluoric acid is used, a spill management process must be available along with the relevant equipment to deal with a spill.

The spill management process should be structured on the ANU Laboratory Spill Management Guidelines (available from the OHS Unit).  A spill control kit should include -

• Personal Protective Equipment (safety glasses gloves, PVC apron or lab coat, good footwear, respirator with acid gas cartridges).
• A form of calcium for binding with the fluoride.  Eg. slaked lime, gypsum, calcium hydroxide, calcium carbonate.  Magnesium salts may also be used.
• Disposal bags or bucket (with lid).
• Additional items as in a normal chemical spill kit – see guidelines.

First Aid Procedures

1. Protect Yourself.  Avoid becoming contaminated or injured yourself. Wear gloves and safety glasses.
   • Gloves – any clean chemical resistant gloves will do.  Avoid contact with the contaminated skin, clothing and equipment.
   • Safety Glasses or goggles to prevent splashes entering the eyes.
   • Respirator - avoid the inhalation of Hydrofluoric acid vapours or fumes during rescue in contaminated areas by wearing suitable respiratory protection (an approved air-purifying respirator fitted with acid gas canisters).  A respirator should not be required for first aiders treating an injured person away from the accident site after the water washing has commenced.
2. Remove.  Immediately remove the casualty from the contaminated area and remove contaminated clothing with gloved hands.
3. Wash.  Dowse the affected area with lots of cold water.  Use a safety shower/eye wash where possible.
4. Treat as described below
5. Report, complete an injury/exposure report http://info.anu.edu.au/policies/_DHR/Procedures/Incident_Reporting.asp.

SKIN - First Aid Treatment

• If a large area is involved - deluge the contaminated areas with water.  Otherwise, flush contaminated skin area with gently running water.  While washing with water, remove contaminated clothing, footwear and leather goods (eg watchbands, belts). 
• Wearing protective gloves the first aider should gently massage the 2.5% calcium gluconate gel into and around the affected area.  If gel is not readily available, continue washing with water.

• Remove to hospital by ambulance accompanied by the Material Safety Data Sheet.  Continue application of gel during transport.
• Continue massaging the gel in with clean fingers until 15 minutes after the pain has subsided. This may be required for several hours, but continue massaging with the gel so long as there is improvement in the symptoms.

EYES - First Aid Treatment

• Using the eyewash station - Irrigate with copious quantities of isotonic saline or water, holding the eyelid(s) open.  Take care not to rinse contaminated water into a non- affected eye.
• Continue irrigation for at least 15 minutes (by the clock).

NOTE: do not use any of the skin treatment preparations for burns of the eye.

• Remove to hospital by ambulance accompanied by the Material Safety Data Sheet.  Continue eye irrigation during transport to hospital. 

INHALATION - First Aid Treatment

• Remove to fresh air.
• Apply artificial respiration and oxygen if 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.

INGESTION - First Aid Treatment

• Do not give anything by mouth if victim is losing consciousness or is unconscious or convulsing.

DO NOT INDUCE VOMITING.

• Give copious quantities of milk, water drinks, milk of magnesia, Mylanta® or effervescent calcium gluconate tablets dissolved in water (in spite of vomiting).  If vomiting occurs naturally, have victim lean forward to reduce risk of aspiration.  Rinse mouth of victim thoroughly with water and spit out rinse water.

• Remove to hospital by ambulance accompanied by the Material Safety Data Sheet.

Further medical treatment advice is available.

References

1. Patty's Industrial Hygiene and Toxicology, Volume 2B: Toxicology, 3rd edition, 1981, John Willey & Sons, USA.
2. BDH Laboratory Supplies 1994/95, Merck Pty Ltd.
3. Environmental & Industrial Health Hazards, a Practical Guide, R.A. Trevethick, 2nd edition, 1980, William Heinemann Medical Books Ltd, London.
4. Significant Incident Summary, Department of Occupational Health, Safety and Welfare, WA.
5. National Occupational Health and Safety Commission (WorkSafe Australia) Guide, Hydrogen Fluoride, 1989. http://www.nohsc.gov.au/
6. Honeywell, Recommended Medical Treatment for Hydrofluoric Acid Exposure, May 2000.
7. National Industrial Chemicals Notification and Assessment Scheme, Priority Existing Chemical Assessment Report, No. 19 – Hydrofluoric Acid, June 2001.
8. Expert discussion within the Occupational Medical Field.

For further information contact:
OHS Officer, e-mail: OHS.Officer@anu.edu.au