Hydrofluoric acid, a solution of hydrogen fluoride gas (HF) in water, is one of the most corrosive and dangerous chemicals encountered in the laboratory. Exposure to HF can cause severe tissue damage and even death. The fluoride ions in HF readily bind calcium and magnesium, reducing their levels in the blood, resulting in hypotension and cardiac effects.¹ Deaths have been reported from concentrated acid burns (involving ≥ 50% HF solutions) to as little as 2.5% of body surface area, which is equivalent to approximately one hand and forearm.² In lower concentrations, symptoms may be delayed, which can lead to delayed recognition of exposure and a more severe burn. The following special safety precautions are necessary when using this chemical, regardless if using dilute or concentrated HF.

What are the hazards?

Hydrofluoric acid (HF) exposure is very toxic and can be fatal if not treated immediately. HF is absorbed quickly; however, damage/symptoms can occur hours to days later. Any person exposed to HF must have immediate first aid, followed by immediate medical treatment from a physician. When seeking medical attention bring a copy of this HF Fact Sheet, the Safety Data Sheet (SDS) for the product used, and the Honeywell guide, “Recommended Medical Treatment for Hydrofluoric Acid Exposure” to the Stanford Hospital Emergency Room.

What are the symptoms of exposure?

INHALATION³

• Mild effects include irritation, inflammation, and cough.
• Severe effects include narrowing and swelling of the throat, causing upper airway obstruction.
• Effects may appear immediately or evolve over 12-36 hours.

Skin/eye exposure³

• Exposure to concentrations >50% HF cause immediate and severe painful, throbbing burns with whitish discoloration of the skin. Blisters often form.
• Exposure to concentrations between 20 and 50% may produce pain and swelling, but may not be felt for up to 8 hours following exposure.
• Exposure to concentrations <20% may cause no immediate pain, but serious injury can develop over 12-24 hours.
• Eye exposure can cause destruction or opacification of the cornea, which can result in blindness.
• Pulmonary (lung) effects can result from skin and eye exposures.

How can I protect myself?

ENGINEERING CONTROLS

• Work in a fume hood with the sash opened as little as possible — sash must not be opened beyond the stickered arrow.
• Ensure the nearest emergency safety shower / eyewash is accessible and has been tested in the last month.
• Ensure laboratory fume hood has been certified within the last 12 months and is functioning properly (check sticker on fume hood and inward airflow monitor).

WORK PRACTICES

• Purchase and use the smallest quantities and lowest concentrations necessary.
• Do not submerge hands into HF solutions. Use tweezers, cassettes, and other sample holders. Teflon and polypropylene are compatible materials.
• Establish designated area for HF use and post sign “Hydrofluoric Acid Use Area.” Also post sign on lab door when in use.
• Do not work alone; others present in the laboratory must be familiar with the operation’s hazards and emergency procedures.
• Add acid to water, not water to acid.
• Do not use glass, ceramic, or other incompatible containers with HF.
• Ensure secondary containment and segregation of incompatible compatible chemicals; see SU Compatible Storage Group Classification System.
• Store HF solutions below eye level.

PERSONAL PROTECTIVE EQUIPMENT (PPE)

• Check PPE for damage before using.
• Wear appropriate PPE, which minimally includes:
• Goggles and face shield.
• Butyl rubber, neoprene, or MAPA trionic tripolymer gloves. Verify glove selection based on concentration and potential exposure via SU’s Laboratory Chemical Glove Selection Guidance.
• Neoprene long-sleeve apron if splash/spray is possible.
• Lab coat and closed-toe shoes.

STANDARD OPERATING PROCEDURE (SOP)

• Develop an SOP, which is a set of written instructions that describes in detail how to perform a laboratory process or experiment safely and effectively.
• Review the guidance for prioritizing SOP development.
• Plan the operation to eliminate risk of HF splash/ spray.
• Perform a “dry run” of procedure using non-hazardous materials to identify and correct potential hazards.

HEALTH & SAFETY TRAINING

• Lab personnel must receive:
• General safety training, which includes General Safety & Emergency Preparedness (EHS-4200) and Chemical Safety for Laboratories (EHS-1900).
• Lab-specific training, which includes reviewing the hazards of HF, safety precautions, and emergency procedures. The SOP, Safety Data Sheet (SDS), and this fact sheet can be used for such training.
• Keep training records for at least one year.

Emergency procedures

• Post SU Hydrofluoric Acid (HF) Exposure Response Instructions in labs that store or use HF solutions or gas.
• Ensure 2.5% calcium gluconate gel (intended for dermal exposures) is available in laboratory and stored at the safety shower.
• Ensure gel has an effective shelf life of at least one year.
• Implement a system to refresh your supply of gel before the expiration date.
• Gel can be purchased through many lab safety supply vendors, including Stanford Express.

SPILLS

For spills occurring outside of a fume hood, evacuate the area.

Immediately call EH&S at (650) 725-9999 (286 from School of Medicine phones) to report an HF spill that is health threatening, is outside of the fume hood, is greater than 30 mls, or will take longer than 15 minutes to clean up. Do not use spill kits with kitty litter or sand because HF reacts with silica to produce silicon tetrafluoride, a toxic gas.

See SU’s Laboratory Chemical Safety Toolkit for additional guidance on spills.

SKIN EXPOSURE

1. Immediately flush affected area with water for 5 minutes under emergency shower station. Remove all contaminated clothing while flushing with water.
2. After flushing, apply calcium gluconate to burn site with clean, gloved hand. Continue massaging gel into the burned area of skin every 15 minutes and massaged continuously until pain disappears.
3. Immediately seek emergency medical assistance Call:

• 9-911 from SU phones
• 911 from non-SU phones
• 286 from School of Medicine phones

Or, take victim to seek medical evaluation at Stanford Hospital Emergency Room.

INHALATION

For emergency medical assistance, call:

• 9-911 from SU phones
• 911 from non-SU phones
• 286 from School of Medicine phones

Or, take victim to seek medical evaluation at Stanford Hospital Emergency Room.

EYE EXPOSURE

1. Immediately flush eyes with water for at least 15 minutes under emergency eyewash. If only one eye is affected, be careful not to flush contaminated water into the other eye.
2. For emergency medical assistance, call:

• 9-911 from SU phones
• 911 from non-SU phones
• 286 from School of Medicine phones

Or, take victim to seek medical evaluation at Stanford Hospital Emergency Room. If possible, provide continuous irrigation during transport.

INGESTION

1. Rinse mouth with cold water. Do not induce vomiting.
2. If the victim is conscious, have them drink lots of water to dilute the acid.
3. For emergency medical assistance, call:

• 9-911 from SU phones
• 911 from non-SU phones
• 286 from School of Medicine phones

Or, take victim to seek medical evaluation at Stanford Hospital Emergency Room.

Reference

¹ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7108671/

² https://emedicine.medscape.com/article/773304-overview

³ “Medical Management Guidelines for Hydrogen Fluoride”. Agency for Toxic Substances and Disease Registry.