Using Hydrofluoric Acid
Hydrofluoric Acid (CAS#7664-39-3), or HF, is one of the most aggressive and corrosive acids known and one of the most dangerous chemicals on our campus. It is used in a variety of applications including preparing plates for semiconductor research, mineral processing, metal finishing, etching glass and manufacturing of electrical components. HF exposures require immediate specialized first aid and emergency medical treatment.
Both anhydrous hydrofluoric acid (hydrogen fluoride) and its solutions are clear, colorless liquids. HF is similar to other acids in that the initial extent of a burn depends on the concentration, the temperature and the duration of contact with the acid.
Hydrofluoric Acid concerns
- HF is very aggressive physiologically because the fluoride ion readily penetrates the skin, causing destruction of deep tissue layers. Unlike other acids which are rapidly neutralized, this process may continue for days if left untreated. Skin contact with HF can cause serious, penetrating burns of the skin that may not be painful or visible for several hours.
- When exposed to air, concentrated solutions and anhydrous HF produce pungent vapors which are especially dangerous.
Signs and Symptoms of HF Exposure
Strong HF acid concentrations (over 50%), particularly anhydrous HF, cause immediate, severe, burning pain and a whitish discoloration of the skin that usually proceeds to blister formation.
In contrast to the immediate effects of concentrated HF, the effects of contact with more dilute solutions or their vapors may be delayed. Skin contact with acid concentrations in the 20% to 50% range may not produce clinical signs or symptoms for one to eight hours. With concentrations less than 20%, the latent period may be up to twenty-four hours.
The usual initial signs of a dilute solution HF burn are redness, swelling and blistering, accompanied by severe throbbing pain.
Burns larger than 25 square inches (160 square cm) may result in serious systemic toxicity.Eye Contact
HF can cause severe eye burns with destruction or opacification of the cornea. Blindness may result from severe or untreated exposures.
Acute symptoms of inhalation may include coughing, choking, chest tightness, chills, fever and cyanosis (blue lips and skin). All individuals suspected of having inhaled HF should seek medical attention with observation for pulmonary effects. This includes any individuals with HF exposure to the head, chest or neck areas.
It has been reported that pulmonary edema may be delayed for several hours and even up to two days. For this reason, it is recommended that all individuals with such exposures be hospitalized for observation and/or treatment. If there is no initial upper respiratory irritation, significant inhalation exposure can generally be ruled out.Ingestion
If HF is ingested, severe burns to the mouth, esophagus and stomach may occur. Ingestion of even small amounts of dilute HF has resulted in death.
The reaction of fluoride with body calcium is one of the major toxic effects and forms the basis for many treatment recommendations.
One of the most serious consequences of severe exposure to HF by any route is the marked lowering of serum calcium (hypocalcemia) and other metabolic changes, which may result in a fatal outcome if not recognized and treated. Hypocalcemia should be considered a potential risk in all instances of inhalation or ingestion, and whenever skin burns exceed 25 square inches.
Treatment for shock may also be required.Using HF
The LSF/PI of a lab using HF must:
- Assign a Designated Work Area
In all labs that use HF, a chemical fume hood must be designated as the work area for HF. All work with HF must take place in the designated fume hood.
- Post a highly visible “Designated Work area” sign, containing the information below, in a prominent position in the work area, usually on the front of the fume hood.
- Assign a Designated Work Area
Danger – Designated Work Area
for Hydrofluoric Acid (HF)
all use of HF must take place in this designated work area
Only authorized individuals using proper
PPE may work with Hydrofluoric Acid
For additional information contact AU EH&S 2190
- Ensure the following Emergency Equipment and Information is available.
- Post phone location, emergency phone numbers, process shut down/evacuation procedures, first aid procedures
- Eyewash/shower - The lab must be equipped with an eyewash/safety shower (may be located in hallway).
- First Aid Kit - A HF first aid kit must be immediately available that includes 2.5% calcium gluconate gel, a liquid antacid, proper gloves. Replace these items with new stock annually.
- Spill Kit - An HF spill kit must be available with calcium compounds such as calcium carbonate, calcium sulfate or calcium hydroxide and/or specific HF spill pillows along with proper PPE and other spill materials appropriate for HF spills. Sodium bicarbonate should never be used since it does not bind the fluoride ion and can generate toxic aerosols.
- SOP - A SOP must be written for your specific application and posted or readily available near the designated area.
- SDS - A hard copy of the SDS must be available. Provide EMT/transport personnel with HF SDS and other information for hospital.
- Provide proper training. See Section 126.96.36.199 Employee Training
- All users of HF, and all workers in a lab where HF is used, must be properly trained.
- Ensure proper labeling
- Maintain original container labels and label all non-original, secondary containers according to AU labeling policies.
- Ensure proper PPE is available. The following PPE is required for HF use:
- Rubber or plastic apron
- Plastic arm coverings
- Gloves – do not use latex gloves, always double glove with proper type of glove
- Incidental use - double glove with heavy 22 mm nitrile exam gloves and re-glove if any exposure to gloves
- Extended use – heavy neoprene or butyl rubber over nitrile or Silvershield®glovesPVC or See Glove Selection Chart and/or SDS.
- Wash off gloves with water before removing them, discard used gloves, after rinsing with water, into a trash receptacle. If gloves are significantly contaminated with HF, discard into a hazardous waste disposal container to prevent secondary contamination to persons using regular trash receptacles.
- Thoroughly wash hands after glove removal and check hands for any sign of contamination.
- Splash goggles and a face shield
- Closed toed shoes that cover the foot, long pants, long sleeve shirt with a high neck (no low cut) and protective lab coat (wear clothes and shoes that cover as much skin as possible).
- Depending on the work involved, respiratory protection may be recommended; contact EH&S.
Store in tightly closed polyethylene containers, never glass. Use plastic secondary containment. Store HF containers in an acid cabinet labeled for HF storage. If the designated fume hood has an acid cabinet under it, store the HF there; do not store in the fume hood
HF Safe Practice Guidelines
- Substitute a less hazardous substance for HF or use a less concentrated solution if possible.
- Never work alone with HF, use the buddy system.
- Use a plastic tray while working with HF for containment in case of a spill.
- Keep HF containers closed; HF vapors etch the hood sash glass making it hard to see through. If this occurs, consider replacing sash glass with a polycarbonate sash.
- Be sure you are properly trained.
- Wear proper PPE.
- Work with the fume hood sash as low as proper flow rate allows (95-125fpm)
- Depending on the work involved, respiratory protection may be recommended. Contact EH&S at 2190 for more information.
What to Do for HF Exposure
Speed of treatment is of the utmost importance. Delay in first aid or medical treatment will likely result in greater damage. Victim should yell for help then immediately start first aid procedures and immediately seek medical attention. Call for emergency assistance and transport to the hospital. Wear appropriate double gloves (not latex) to prevent secondary HF burn when assisting victim. Bring the SDS with you to the hospital.
- Immediately start rinsing under safety shower or other water source and flush affected area thoroughly with large amounts of running water. Speed and thoroughness in washing off the acid is of primary importance.
- Begin flushing even before removing contaminated clothing. Remove contaminated clothing while continuing to flush with water.
- Rinse with large amounts of water for 5 minutes and then massage 2.5% Calcium gluconate gel into the affected area. If alone, call 911 at this time. Note: Wear proper double gloves to prevent a possible secondary HF burn when applying the calcium gluconate gel.
- If 2.5% Calcium gluconate gel not available, continue rinsing until medical help arrives.
- While the victim is rinsing, someone should call for emergency assistance.
- Do not rub eyes or keep eyes closed.
- Immediately flush eyes for at least 15 minutes holding eyelids open and away from the eye, remove contact lenses if possible, but flushing should not be interrupted.
- If alone, call for emergency assistance then resume flushing until medical personnel arrive. Medical personnel will remove contact lenses.
Do not apply Calcium gluconate gel to eyes.
Medical personnel should apply 1% calcium gluconate solution repeatedly to irrigate the eyes. Ice water compresses may be applied to the eyes while transporting the victim.
If someone else in the lab has suffered eye contamination, lead them to the eyewash and activate the unit, help start the flushing as outlined above then call for medical assistance and go back to assist the person until help arrives.
Immediately move victim to fresh air and call for emergency assistance
Call 911 and get immediate medical attention. Ingestion of HF is a life-threatening emergency.
- Drink large amounts of water as quickly as possible to dilute the acid. Do not induce vomiting. Do not give emetics or baking soda. Never give anything by mouth to an unconscious person.
- Drink 10 ounces of milk of magnesia, Mylanta® or Maalox®.
HF Spill and Disposal
HF-specific spill control materials are required for spills. If HF is spilled, leave the room and call for emergency assistance. If a very small spill occurs in the hood and you feel comfortable cleaning it up, then:
- Wear the appropriate PPE for HF.
- Pour a calcium compound such as calcium carbonate or place a HF spill pillow on the spill and wait for it to soak up.
- Transfer the waste to a high quality plastic container (such as HDPE) that seals tightly, never use a glass container.
- Properly label, store and dispose of as hazardous waste according to AU procedures.
- Containers of HF may be hazardous when empty since they retain product residues.
- Chemical Hygiene Plan, Cornell University, 5/25/05.
- Hydrofluoric Acid Product Literature, Honeywell Inc.
- Safety data sheet, Hydrofluoric Acid, 47-51%,ACC#11171, Fisher Scientific, 10/22/2007.
- Safety data sheet, Hydrofluoric Acid #HF-0002, Honeywell, Inc., January 2004.
- Woods Hole Oceanographic Institute Chemical Hygiene Plan, Hydrofluoric Acid - Safety Guideline, 6/27/05.
- Recommended Medical Treatment for Hydrofluoric Acid Exposure Ver. 1.0, Honeywell Inc., May 2000.