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HF Gas and its Sensor

Intro to Hydrogen Fluoride Gas

Hydrogen fluoride is an inorganic compound with the formula HF and is a colorless gas at temperatures above 67°F / 19°C or liquid at colder temperatures, both with a pungent odor. Even in liquid form, it fumes creating a very dangerous breathing hazard. When this compound is dissolved in water it's known as hydrofluoric acid. Hydrogen fluoride can be released when other compounds, such as ammonium fluoride (NH4F), are combined with water.

HF is used as a precursor to creating other chemical compounds from polymers and pharmaceuticals such as Prozac. Another common use for it is in the petrochemical industry as a component of superacids.

One of the common dangers to industrial workers is that it's extremely corrosive to a wide range of materials. HF can cause painful burns on the skin and severe eye damage. 

Gas Characteristics

  • Acidic
  • Extremely toxic
  • Highly corrosive to metals, glass, silica, silicic acid, and tissue.
  • Soluble in water or alcohol.
  • Colorless gas or fuming liquid (below 67°F) with a pungent irritating odor.
  • HF is lighter than air but if released, creates a vapor that is heavier than air. 
  • A common aqueous solution is called hydrofluoric acid
  • Reacts violently with bases and is corrosive to most metals forming an explosive gas
  • The molecular formula is HF.
  • Also known as anhydrous fluoride, aqueous hydrogen fluoride, HF-A, fluorane, and hydrofluoric acid.
  • CAS 7664-39-3
icon ghs whmis toxic depicting dangers of sulfur dioxide released in industrial processes involving chemical hazards
GHS Health Hazard Hydrogen Fluoride

Industrial HF hazards and sources

  • The majority of hydrogen fluoride manufactured worldwide is made from fluorspar and sulfuric acid.
  • Manufacturing: HF is a precursor to creating many fluorine-containing chemicals used in the production of refrigerants, herbicides, pharmaceuticals, high-octane gasoline, aluminum, plastics, electrical components, and fluorescent light bulbs.
  • Steel and metal production: Aqueous hydrofluoric acid is used in stainless steel pickling, metal coatings and exotic metal extraction
  • Metal Industries - extraction, processing, and refining. 
  • Laboratory supplies e.g. laboratory diagnostics or consumables, solvents, and reagents used in experiments or laboratory.
  • Cleaning agent or solvent - automotive cleaners, rust removers, inhibitors for ceramics and fabrics, and water spot removers.
  • Electrical power plants: Fluoride is present in coal and oil so can combine with hydrogen to produce HF.
  • Acid and alkali cleaning of metals.
  • Petroleum Production and Refining : used as a catalyst in the production of gasoline
  • Production of aluminum, fluorocarbons, cryolite, and uranium hexafluoride
  • Semiconductor manufacturing 
  • Glass manufacturing/welding and quartz purification.
  • Insecticide manufacturing
  • Sea salt aerosol
  • Electroplating, enameling, glassblowing

A spill and explosion of HF in South Korea killed 5 employees, hospitalized 18 and 12,243 in the vicinity needed medical attention, including 416 firefighters.

Korea Institute of Public Administration

High Risk Scenarios

  • Hydrofluoric acid that is more than 40% hydrogen fluoride fumes in the air.
  • High exposure can cause Fluoride poisoning with stomach pain, weakness, convulsions, collapse, and even death.
  • Long-term exposure to high concentrations can cause deposits of fluoride in the bones and teeth called "Fluorosis". This can cause bone pain, fractures, disability, and mottling of the teeth.
  • Exposures can happen during natural disasters if storage facilities or containers are damaged containing hydrogen fluoride.
  • Has been used as a chemical terrorism agent.
  • HF is released from active volcanoes putting those in the vicinity at risk

HF Sensor Info

Type: Electrochemical
Range: 0-10 ppm (0.1ppm resolution)

Alarm Levels

Low Alarm: 2.5 ppm
High Alarm: 5 ppm
STEL — 15 minutes — Short-Term Exposure Limit: 2.5 ppm
TWA  — 8-hour time-weighted average: 2.5 ppm

Blackline devices that can detect HF

Questions about the detection of HF?


Special Applications and Considerations

  • Corrosion - contact can severely irritate and burn the skin and eyes with permanent damage.
  • Contact with HF can irritate the nose and throat. Inhaling can irritate the lungs. Higher exposure can cause a fluid build-up in the lungs (pulmonary edema). 
  • Common exposure symptoms are headaches, dizziness, nausea, and vomiting. Long-term exposure to high concentrations can cause "Fluorosis" — deposits of Fluoride in the bones and teeth.
  • Ingesting a small amount of highly concentrated hydrogen fluoride will affect major internal organs and potentially be fatal. 
  • Fluoride used in water and dental products to prevent cavities in teeth is a shallow concentration.
  • Potential exposure can be tested from urine, liver, and kidney function tests, chest x-rays, or Bone Density (DEXA) Scans.
  • Smoking can worsen respiratory conditions experienced from chemical exposures.
  • Handling - hydrogen fluoride reacts violently with strong bases such as sodium hydroxide and potassium hydroxide. HF reacts with water and steam to produce toxic and corrosive gases. Also reacts with metals like iron and steel to produce flammable and explosive hydrogen gas. It's not compatible with odizing agents.
  • PPE - if there is an exposure risk of over 0.5ppm use a NIOSH-approved full facepiece respirator with an acid gas cartridge for hydrogen fluoride or SCBA. Wear non-vented impact-resistant goggles for eye protection. Over 5ppm exposure requires a supplied air respirator with a full facepiece in a pressure-demand or positive-pressure mode SCBA. 
  • Symptoms may be delayed by low concentrations of exposure on the skin since HF affects the nervous system. 

Health Risks and Handling of HF

1 - 2 ppm OR under 20% HF solution
Irritation of the eyes, nose, and respiratory tract. Symptoms may be delayed for 24 hours and are often reported after significant tissue injury.
2.5 - 6 ppm OR 20%-50% HF solution
Skin and eye irritation. Skin redness, burning, and pain may not appear for several hours following exposure. Can also cause headaches, dizziness, nausea and vomiting, stomach pain, chest tightness, and weakness. Often reported after significant tissue injury.
7 - 27 ppm OR over 50% HF solution
Burns are visible almost immediately after exposure. Rapid tissue destruction, with blistering, and acute whole-body systemic effects; lung damage is common.
30 ppm
Immediately dangerous to life and health. Exposure to more than 1% of the body's surface area may lead to systemic toxicity.
  • If INHALED move the impacted person to fresh air. Begin rescue breathing. Seek medical attention for 24-48 hours after breathing overexposure, as pulmonary edema may be delayed. Inhaling HF can irritate the lungs causing coughing and shortness of breath. 
  • If SKIN CONTACT is made immediately wash the skin with water. Apply 2.5% Calcium Gluconate gel to the affected skin. Massage the gel into the skin while wearing rubber gloves. Continue to reapply until the pain is relieved. Seek medical attention. Contact can cause skin irritation and severe deep-tissue burns. The burn may even be delayed in developing by a few hours.
  • If the EYES are contacted, immediately wash the eyes with large amounts of water for at least 30 minutes. Get medical attention immediately.
  • If INGESTED, have the individual take several calcium or magnesium tablets or liquid antiacid with 1-2 glasses of water or milk to neutralize. Do not induce vomiting.
  • Please make sure to evacuate the area immediately.
    • Isolation distance:
      • Spill: 100 meters or 330 feet
      • Fire: 1600 meters or 1 mile
  • Remove ignition sources if safe.
  • Ventilate the area.
  • Stop the flow of gas if it's safe to do so. Remove leaking cylinders outside.
  • For a liquid spill, allow dispersing, then cover it with sodium carbonate or an equal mix of soda ash and slaked lime.
  • Water spray can be used to absorb hydrogen fluoride vapors escaping from leaking containers.
  • Don't wash into the sewers.
  • You may need to contain HF as hazardous waste. Contact your local environmental protection agency. 


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