Hydrofluoric Acid: What You Need to Know

Incidents involving hydrogen fluoride, or hydrofluoric acid, are not common, but the consequences of exposure to this compound by any means can be devastating. This little-known acid has unique properties that make it extremely dangerous to emergency personnel and others. Frequently mistaken for or confused with hydrochloric acid, hydrofluoric acid should be referred to as HF.

I became interested in HF while working in an oil refinery that uses it as a catalyst to make high-octane gasoline. As a paramedic, I found the effects of HF on the human body fascinating. I learned what I could about it and began teaching HF safety to my coworkers.

Then, in 2001, I was involved in an HF incident in which I was seriously exposed. I had been sprayed with anhydrous HF at approximately 150 pounds of pressure when a ¾" pipe broke at an ell as I was preparing to remove a plug. The HF had eaten the threads inside the ell and the weight of my pipe wrench caused the damaged pipe to give way, spraying both my legs just below my groin, and my right forearm. That exposure began a battle for my life that continues today.

Luckily, our local EMS and emergency facility had been trained on the dangers of this acid and proper treatment. Many EMS and ER personnel have probably never heard of this dangerous compound, but all emergency services, fire or law enforcement personnel who operate near and may be called to respond to any facility that uses or manufactures a form of HF should receive yearly training on treatment for HF exposure. This information should be available from your county LEPC.

Anhydrous hydrogen fluoride (HF) is an inorganic, corrosive compound with many industrial and commercial uses. It is manufactured by heating purified fluorspar (calcium fluoride) with concentrated sulfuric acid to produce the gas, which is then condensed by cooling or dissolving in water. It can also be refined as a by-product of the production of phosphoric acid, which is derived from the mineral apatite. Apatite sources typically contain a small amount of fluorite. The acid hydrolysis of fluorite-containing minerals generates an impure gas stream consisting of sulfur dioxide, water and HF. Separating gases from solids and treating them with sulfuric acid and oleum produces anhydrous HF. HF can also be released when other fluoride-containing compounds, such as ammonium fluoride, are combined with water or when certain plastics are exposed to fire conditions, creating carbonyl fluoride (the fluorine analog of phosgene).

HYDROFLUORIC ACID FAST FACTS

Hydrogen fluoride is available commercially either in an anhydrous (water-free) state or in water solutions of various concentrations. At higher concentrations, HF is a colorless gas or a fuming liquid. HF may be known as Hydrogen fluoride (UN 1052), hydrofluoric acid (UN 1790) or fluorohydric acid. Identification numbers are CAS number 7664-39-3, UN: 1052 or RTECS: MW7875000. Main Manufacturers/main importers are DuPont (US), Allied (US) and Honeywell (US).

Its physical properties are:

  • Molecular weight: 10
  • Boiling point: Gas at temperatures above 19°C
  • Auto-ignition: Not relevant
  • Vapor pressure: 150mm (70% solution at 26.7°C); 70mm (70% solution at 20.0°C)
  • Solubility: Aqueous solutions to 70%
  • Explosive limits: Not applicable--non-flammable (BLEVE hazard if container subjected to fire conditions)
  • Shipping name: Hydrogen fluoride, anhydrous (1052), hydrofluoric acid, with not more than 60% strength (1790)
  • Identification number: 1052 (hydrogen fluoride, anhydrous) (Guide 125), 1790 (hydrofluoric acid) (Guide 157)
  • Hazardous class or division: 8 (1052)
  • Subsidiary hazardous class or division: 6.1, Inhalation hazard (1790)
  • Label: Corrosive, Poison (toxic) (1052), Corrosive, Poison (Toxic), Inhalation Hazard (1790)

Hydrogen fluoride is used in solution form in glass and metal etching, industrial and home cleaners and rust removers, and in manufacturing electronics. Full strength, it is used to manufacture high-octane fuels in oil refineries. Other major industrial uses of hydrogen fluoride include synthesis of fluorocarbons (e.g., freon and Teflon) and production of aluminum fluoride and synthetic cryolite for use in aluminum refining. It is also employed in refining uranium for use as a nuclear fuel, in manufacturing various organic chemicals, in producing stainless steel, and for various other applications such as:

  • Propellants and solvents
  • Insecticide and fertilizer production
  • Manufacture and reduction of chlorides
  • Brewery to control fermentation
  • Fabric industry for stain removal
  • Leather industry for tanning
  • Drug and dye production
  • Manufacture of semiconductors.

Present household uses include:

  • Rust remover
  • Aluminum brighteners
  • Heavy-duty cleansers.

THE DANGERS OF HYDROFLUORIC ACID

Although considered a weak acid, HF is one of the most dangerous inorganic acids known. Burns of as little as 1% body surface area (BSA), or approximately 25 sq in (about the size of the palm of your hand), have been known to be fatal due to the acid's unique properties.

HF penetrates tissue more quickly than typical acids. Because of this ability, systemic toxicity can occur by dermal, ocular, inhalation and oral routes. When human tissue is exposed to concentrated HF, the molecules disassociate into individual hydrogen and fluoride ions. The hydrogen ion burns like any other acid. The fluoride ion quickly penetrates dermal and muscle tissue and reacts with the calcium and magnesium found within the body, rendering these ions useless. Major organs or systems that are especially vulnerable to damage are the heart, liver, kidneys and nerves. Exposures of 6%-8% BSA burns of concentrations above 50% HF almost always prove fatal within hours.

At lower concentrations, death can still occur if definitive treatment is not sought quickly. HF interferes with nerve function, so burns from lower concentrations may not be initially painful. Accidental exposures can go unnoticed for hours or even days, delaying treatment and increasing the extent and seriousness of the injury. This is extremely dangerous, because victims may not recognize that they are injured. Death may result from the associated hypocalcemia or hypomagnesemia if too much damage is done before treatment is sought.

After I was burned, the HF acid penetrated the Nomex coveralls I was wearing under my coat. (The photo of my left leg shows the flame pattern caused by the splatter from acid hitting my right leg.) The fluoride immediately penetrated the skin and bound to the calcium and magnesium in my blood and body tissues, which caused severe heart arrhythmias about 1 hour post-burn.

I was flown by helicopter to a burn center at Hillcrest Hospital in Tulsa, Oklahoma. There, despite the fact that I had at least 16% BSA, the burn center doctors and cardiologist refused to let me die. They called all over the world, looking for help from HF specialists and were told, "Make him comfortable, let his family say goodbye, and let him go." Thank God, they refused and kept working on me. They stopped counting the defibrillator shocks after 15. (By the way, THAT HURTS!!!) By the grace of God, a very dedicated nurse, and those stubborn doctors, I am still here.

The pictures shown are three days post-burn, just before debridement surgery. All the damaged muscle tissue had to be cut away.

TREATMENT OF HYDROFLUORIC ACID BURNS

Treat all HF burns very aggressively with calcium gluconate, with delivery depending on mode of exposure. Calcium gluconate offers another source of calcium, slowing or stopping the HF's attack on the body's own calcium and magnesium stores. Immediate and thorough rinsing with copious amounts of water while removing all clothing is essential. Treat HF dermal burns with a 15-minute water flush and constant application of a 2.5% calcium gluconate gel. However, due to its absorbing nature, medical treatment should not be delayed. Flushing for more than 15 minutes is of little value. If the burn is from concentrated HF, medically trained personnel should administer 10% calcium gluconate injections beneath the burn.

Calcium gluconate is rarely carried by EMS, but should be available with yearly continuing education to anyone who may respond to an incident involving HF. Most hospital emergency rooms that are located near facilities that use or manufacture hydrofluoric acid have in-service training on HF and recognize the importance of having calcium gluconate readily available. HF manufacturers often offer training to police, fire, EMS and local hospitals that might respond to incidents involving HF.

Burns to digits: Local infiltration of digits is not recommended, because of pain, disfigurement and potential complications. Alternative treatment methods follow:

  • IV regional calcium gluconate: 10-15 mL of 10% calcium gluconate plus 5000 units of heparin diluted up to 40 mL in 5% dextrose. Use a Bier ischemic arm block technique to infuse the solution intravenously. Release the cuff when any of the following conditions first occur: (1) pain from the digits resolves; (2) the cuff becomes more painful than the burn; or (3) 20 minutes of ischemic time elapses. Treatment can be repeated after 4 hours, if needed. Continuous ECG and clinical monitoring are essential during this procedure.
  • Intra-arterial calcium gluconate: Place an arterial catheter in the radial or brachial artery to perfuse the affected digits. Infuse a solution of 10 mL of 10% calcium gluconate in 40 mL of 5% dextrose over a 4-hour period. Follow with further infusions repeated after 4-8 hours, if necessary. Several treatments may be needed. Exercise great care to ensure that the catheter is appropriately placed intravascularly (i.e, by continuous waveform analysis), as tissue necrosis and digit loss have occurred following extravasation of calcium salts. Continuous ECG and clinical monitoring are essential during this procedure.

Burns to the eyes should immediately be flushed with water and treated with 1% calcium gluconate in normal saline. Any burns to the eyes should be seen by an ophthalmologist, no matter how slight the injury seems.

If inhaled, HF can cause severe difficulty in breathing within seconds. Immediate treatment may be essential for survival. Administer nebulized 2.5% calcium gluconate with 100% oxygen by bag-valve mask as soon as possible, because victims may be unable to effectively breathe on their own. Intubation equipment should also be available. Avoid mouth-to-mouth rescue breathing, as secondary burns may occur.

Seek definitive care at an emergency facility familiar with treating HF burns as soon as possible. Be aware that the runoff from washing burns should be treated as contaminated. Do not allow this water to pool under the victim or contact any rescuer. No victim should be placed in an ambulance or taken to an emergency facility until decontamination is complete. Secondary burns to emergency responders, EMS and ED personnel have been reported due to incomplete decontamination. Be sure to include any information on HF and all available medical information on the victim(s) for the emergency facility.

Serum calcium levels should be drawn as soon as possible and closely monitored, along with other electrolytes like magnesium and potassium, to gauge treatment effectiveness. Normal total serum calcium levels in adults are 9-10.5 mg/dL (2.2-2.6 mmol/L). Levels may vary from facility to facility. Cordarone (amiodarone) may be given to combat the ventricular arrhythmias associated with HF exposure. Traditionally, lidocaine has been ineffective.

Below is an example of HF acid calcium gluconate antidote dosages for various routes of exposure.

  • Skin: Gel=10% CG in X3 water-soluble jelly (25 ml 10% CG in 75 ml KY jelly=100ml of 2.5% CG)
  • Injection: 10% CG (calcium gluconate) at 0.5ml/cm2 with a small-gauge needle (#30). Do not use local anesthetics, as pain is a good indicator of effective treatment.
  • IV: 10% CG in normal saline at a dose of 0.1-0.2 ml/kg up to 10 ml repeated until serum calcium levels, ECG tracing or symptoms improve.
  • Intra-arterial for digit burns: 10-15 ml 10% CG+5000 units heparin in 40 ml D5W given over 4 hrs.
  • Eye Irrigation: 1% CG-NS (50 ml 10% CG in 450 ml NS)
  • Inhalation: 2.5% CG nebulized (25 ml 10% CG in 75 ml NS=100 ml of 2.5% CG)

Some safety tips and tricks for treating HF burns are:

  • When treating burns on hands or fingers, apply a liberal amount of calcium gluconate gel to the area, then have the victim put on a vinyl glove and wiggle his fingers, opening and closing the hand constantly. Change the gel and glove every 5 minutes by removing the glove, wiping off the gel, then reapplying as before.
  • The gloved hand may be placed in a bowl of ice water to help slow the dissociation of the fluoride ion. DO NOT use crushed ice. DO NOT leave hand in ice water for more than 3-5 minutes. Remove the hand and allow rewarming, then reintroduce it back into water for another 3-5 minutes. Ice may also be applied to burns on other places of the body, where appropriate.
  • Eye irrigation can be done using a nasal cannula and an IV set. Lie the victim down in a place that will not allow the irrigation solution to pool anywhere under the victim or endanger the rescuer. Mix the irrigation solution in a 500 ml bag of normal saline. Connect the cannula tubing to the IV tubing using a tubing extension adapter (you may have to cut off the end of one or both tubes, depending on the type and manufacturer). Tape the connection securely. Tape the part of the cannula that normally goes in the nostrils to the bridge of the nose, with one opening on each side. Be sure the openings are pointed into the eyes. Run the drip set at a rate that allows for a steady stream of fluid to enter the eyes.
  • Remember, any excess runoff from flushing may be contaminated with HF. Be sure it is contained and not allowed to pool under the victim's head or body, or to contact rescuers.
  • Never use anesthetics when treating an HF burn. Pain is a good indicator of effective treatment.
  • When treating anyone suspected of having an HF burn, always wear protective gloves approved for use with HF acid. Change gloves often, especially before touching non-contaminated objects such as the container of calcium gluconate gel, box of gloves, IV bags, tubing sets, tape, or before working with any other victims.
  • Be alert for runoff from any irrigation used. This fluid must be contained. Treat collected runoff as hazardous waste and wear appropriate personal protective gear. This may include chemical-resistant clothing, such as aprons or jackets, full face shield or goggles, boots, and overalls or pants.
  • Double bag all contaminated clothing and equipment for proper cleaning or disposal.
  • People who survive after being severely injured by breathing in hydrogen fluoride may suffer lingering chronic lung disease.
  • Burns caused by concentrated hydrogen fluoride may take a long time to heal and may result in severe scarring.

As stated earlier, all victims should be seen in an emergency facility familiar with the treatment protocols for HF exposures. Standard treatment should include constant EKG monitoring, O2, and prophylactic eye and breathing treatments. Intravenous access should be established, and the victim should be monitored for the first 24 hours or longer, depending on exposure. Do not rely on patient presentation as a determination of care needed.

The long-term effects of a significant HF burn are still unknown. I am an unwitting guinea pig of sorts. So far, I have experienced end-stage kidney failure, osteoporosis, peripheral neuropathy, peripheral edema due to a compromised lymphatic system, a compromised immune system and other health problems. This doesn't even begin to account for the severe pain and disfigurement I continue to have. The best way to avoid this trouble is to be prepared and follow a well-planned and practiced response.

TRANSPORT OF HYDROFLUORIC ACID

Acid tank cars for rail transport are of the tank-within-a-tank design. The rail tank cars for HF have product-specific linings to protect the inner tank from the product, and have acid-resistant fittings and unloading systems. Semi-trailer loading and unloading fixtures are located on top of the trailer, usually at the back. Most over-the-road transporters of HF use a two-man crew who are trained and equipped for loading and unloading, as well as handling small spills.

BIBLIOGRAPHY

Blanchard K. Hydrofluoric Acid Spells Health Risks on the Highway. Traveler Health, March 21, 2009. http://www.emaxhealth.com/1020/41/30027/hydrofluoric-acid-spells-health-risks-highway.html

HF Medical Book. Honeywell International Inc., January 04, 2010, http://www51.honeywell.com/sm/hfacid/common/documents/HF_medical_book.pdf

Hydrofluoric Acid. Centers for Disease Control and Prevention, Public Response Hotline (CDC), 800-CDC-INFO, 888-232-6348 (TTY), E-mail inquiries: cdcinfo@cdc.gov

Hydrofluoric Acid. Centers for Disease Control and Prevention (CDC), National Institute for Occupational Safety and Health (NIOSH), Pocket Guide to Chemical Hazards.

Hydrofluoric Acid. Honeywell International Inc. Jan 4, 2010. http://www51.honeywell.com/sm/hfacid/index.html

Hydrofluoric Acid. Wikipedia. http://en.Wikipedia.org/wiki/hydrofluoric

Hydrofluoric Acid Burns. Garry Wilkes, MD, Director, Emergency Medicine, Adjunct Associate Professor, Edith Cowan University, Department of Emergency Medicine, Bunbury Health Service, Nov. 19, 2005.

Hydrogen Fluoride. Edelman Philip, MD, Chief Toxicology and Poison Control, University of California Irvine Medical Center, Orange, CA, May 1995.

Kratz A, Ferraro M, Sluss PM, et al. Case records of the Massachusetts General Hospital: Laboratory values. N Engl J Med 351(15):1549-1563, 2004.

Martin H, Muller MJ. Hydrogen Fluoride. MJA 176(6):296, 2002. Hydrogen Fluoride, IPCS INCHEM Home, http://www.inchem.org/documents/pims/chemical/hydfluor.htm

Pyo RT. Hydrofluoric Acid Burns: A Brief Overview, Wikipedia http://en.Wikipedia.org/wiki/Hydrofluoric_Acid#cite_note4

Bradley Denney, RN/MICT, has been involved with the fire service for over 38 years and EMS for over 36 years. He has worked as a frontline firefighter and EMT to assistant fire chief and hazardous materials technician and paramedic. In 2007, he became a registered nurse. He has taught hazmat courses for fire, law enforcement and EMS, and taught HF-specific classes at the Kansas HazMat/WMD Symposium in 2006 and 2007. He also has over 15 years of experience working with HF acid in the oil refining industry. He was instrumental in initiating first aid protocols in the refinery emergency facility setting that ultimately would save his life.

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