STANDARD OPERATING PROCEDURE: Hydrofluoric Acid  

Oregon State University, Department of Chemistry
Standard Operating Procedure (SOP): Safe Handling of Hydrofluoric Acid (ver. 1.0)
Author: Mas Subramanian (mas.subramanian@oregonstate.edu)
Safety Web Inception Date: 2/18/2010
Revised: N/A

Chemistry Department Safety Office: Gilbert Hall Room 153
Emergency Medical Services: 911
Campus Student Health Center: 7-9355
Poison Control: 9-1-800-222-1222
OSU Environmental Health and Safety: 7-2273
Campus Security: 7-7000

 
   

A. Introduction

Hydrofluoric acid (HF: MSDS) is a solution of hydrogen fluoride in water which has a number of chemical, physical and toxicological properties that make handling this material particularly hazardous. Anhydrous HF is a clear, colorless, fuming, corrosive liquid. HF is also available in the gaseous state. All forms including the solution or the vapor can cause severe burns to tissue. Concentrated hydrofluoric acid is used in the fabrication of electronic components, to etch glass and in the manufacture of semiconductors. It is also a valued source of fluorine, being the precursor to numerous pharmaceuticals such as fluoxetine (Prozac), diverse polymers such as polytetrafluoroethylene (Teflon), and most other synthetic materials that contain fluorine. Dilute hydrofluoric acid solutions are used in some biological staining procedures. Hydrofluoric acid solutions are clear and colorless with a density similar to that of water. The most widely known property of HF is its ability to dissolve glass. It will also attack glazes, enamels, pottery, concrete, rubber, leather, many metals (especially cast iron) and organic compounds. Upon reaction with metals, explosive hydrogen gas may be formed. HF must be used and stored in polyethylene, polypropylene, Teflon, wax, lead or platinum containers. The danger in handling hydrofluoric acid is extreme, as skin saturation with the acid in areas of only 25 square inches (160 cm2) may be relatively painless, yet ultimately fatal. High concentrations of hydrofluoric acid and hydrogen fluoride gas will also quickly destroy the corneas of the eyes.

This SOP should be read and understood prior to the commencement of relevant work and used to complement supervised practical familiarization with the various techniques described.

 
   

B. Hazard identification, PPE, required safety equipment, and emergency response

B1. Hazards: Fluoride ions are both acutely and chronically toxic. Acute effects of HF exposure include extreme respiratory irritation, immediate and severe eye damage and pulmonary edema. Skin, eye, or lung exposure to concentrated (>50%) HF solutions will cause immediate, severe, penetrating burns. Exposure to less concentrated solutions may have equally serious effects, but the appearance of symptoms can be delayed for up to 24 hours. If you are exposed to hydrofluoric acid seek medical attention immediately, even if you do not feel pain. Exposure to hydrofluoric acid can produce harmful health effects that may not be immediately apparent, as follows:

(a) Inhalation: Severely corrosive to the respiratory tract. May cause sore throat, coughing, labored breathing and lung congestion/inflammation.

(b) Ingestion: Corrosive. May cause sore throat, abdominal pain, diarrhea, vomiting, severe burns of the digestive tract, and kidney dysfunction.

(c) Skin Contact: Corrosive to the skin. Skin contact causes serious skin burns which may not be immediately apparent or painful. Symptoms may be delayed 8 hours or longer. The fluoride ion readily penetrates the skin causing destruction of deep tissue layers and even bone.

(d) Eye Contact: Corrosive to the eyes. Symptoms of redness, pain, blurred vision, and permanent eye damage may occur.

(e) Chronic Exposure: Intake of more than 6 mg of fluorine per day may result in fluorosis, bone and joint damage. Hypocalcemia and hypomagnesemia can occur from absorption of fluoride ion into blood stream.

(f) Aggravation of Pre-existing Conditions: Persons with pre-existing skin disorders, eye problems, or impaired kidney or respiratory function may be more susceptible to the effects of this substance.

 

B2. Personnal protective equipment (PPE): The purpose for PPE is to shield the individual in the event of a release of vapor, a spill or other incident. PPE is not a substitute for safe work practices. Eye protection must be used during handling of any quantity of HF. Thick Neoprene or Nitrile gloves or other HF-resistant gloves should be worn. HF burns around the fingernails are extremely painful, difficult to treat, and may require surgical removal of the nail. It is also recommended that an acid resistant suit or apron be used since some clothing can absorb HF solution and maintain it close to the skin.

 

B3. Engineering controls and hydrofluoric acid exposure kit: The ACGIH ceiling limit and OSHA TWA for HF is 3 PPM. Local exhaust ventilation should always be used when working with HF. Before beginning work involving HF an exposure kit should be available and located in the laboratory area. The exposure kit should contain the following items:

(a) Container (tube) of 2.5% calcium gluconate gel. This gel is available from several suppliers. The gel must be inspected at least monthly to ensure that it is available and has not reached the expiration date. If the gel has exceeded its shelf life or has been opened (i.e., used), a new tube must be purchased and the old container discarded.

(b) Two pairs of thick Neoprene or Nitrile gloves.

(c) Copy of this SOP (or an alternate) and MSDS to provide to emergency response personnel.

(d) Calcium Carbonate (antacid tablets).

 

B4. Emergency response: In the event of an accidental exposure to HF take the appropriate action as follows.

B4.1. Skin Exposure

(a) Move the victim immediately under an emergency shower or other water source and flush the affected area with large amounts of cool running water for at least 5 minutes. Clothing, shoes and jewelry should be removed while the water is flowing on to the victim. Goggles should be removed last while the victim is facing the water flow. Colleagues must be EXTREMELY CAREFUL not to become contaminated while assisting the victim. Thick Neoprene or Nitrile must be worn.

(b) While the victim is being rinsed with water, call 911 and inform the emergency dispatcher of the exposure and request emergency transport. Ensure emergency responders and treating physicians are aware of the nature of the chemical exposure. Provide a copy of the MSDS to emergency responders.

(c) After the affected area is flushed with copious amounts of water for at least five minute, apply 2.5% calicum gluconate gel according to this procedure. Massage gel into affected area s. Flush skin surfaces with water f or at least 15 minutes if calcium gluconate gel is not available. In order to prevent cross contamination, the victim should self-apply the calcium gluconate gel. If the victim is unable to self-apply, anyone present can apply the gel after first putting on thick neoprene or nitrile gloves. Do not use latex gloves because they are not an effective barrier against HF. Note the time when the calcium gluconate gel was first applied to the contaminated skin and provide this information to the emergency responders. Re-apply gel every 15 minutes until medical assistance arrives.

(d) After the emergency responders arrive they will call the Emergency Room doctor for instructions and may administer the calcium carbonate tablets (antacid tablets) in the Spill Exposure Kit (see Section B3 above).

B4.2. Eye Exposure

(a) Immediately flush eyes for at least 5 minutes with copious cool flowing water. Call 911, inform the emergency dispatcher of the exposure and request emergency transport. The victim should then be transported to a medical facility. MEDICAL PERSONNAL may apply a sterile 1% calcium gluconate solution to the victim’s eyes after irrigation.

(b) Ensure emergency responders and treating physicians are aware of the nature of the chemical exposure. Provide a copy of the MSDS to emergency responders.

B4.3. Inhalation. If a large volume of Hydrofluoric Acid gas is inhaled:

(a) Immediately remove the victim to clean air. Call 911, inform the emergency dispatcher of the exposure and request emergency transport.

(b) Ensure emergency responders and treating physicians are aware of the nature of the chemical exposure. Provide a copy of the MSDS to emergency responders.

(c) Inhalation of Hydrofluoric Acid fumes may cause swelling in the respiratory tract up to 24 hours after exposure. Persons who have inhaled Hydrofluoric Acid vapors may need prophylactic oxygen treatment and must be seen by a physician as soon as possible.

 
   

C. Handling Procedures for Safe Use of Hydrofluoric Acid

(a) Never use Hydrofluoric Acid when working alone after hours. Hydrofluoric Acid may be used when working alone during normal working hours provided knowledgeable laboratory personnel have been alerted and at least one is in the general vicinity to provide assistance if necessary.

(b) All lab personnel, not just those who will be using Hydrofluoric Acid, must be informed of the dangers of this chemical and the emergency procedures necessary in case of an accident. A sign should be posted to alert people that work with Hydrofluoric Acid is in progress.

(c) All persons who use Hydrofluoric Acid must be made aware of its properties and trained in proper procedures for use and disposal. The Lab Supervisor/PI is responsible for providing this training.

(d) Laboratories which keep or use Hydrofluoric Acid gas or concentrated solutions (>1% Hydrofluoric Acid) must have these emergency procedures on hand as well as the appropriate MSDS.

(e) Laboratories which keep or use Hydrofluoric Acid gas or concentrated solutions (>1% Hydrofluoric Acid) must have an operational safety shower and eye wash in their laboratory. Before beginning any procedure involving Hydrofluoric Acid, make sure the access to the emergency shower and eyewash is unobstructed.

(f) Undergraduate students should never be given the task of mixing Hydrofluoric Acid solutions. Only experienced persons familiar with its properties should handle the concentrated acid.

(g) A small supply of appropriate neutralizer for spills should be kept near the fume hood where the work will be conducted. If a small quantity (100 ml or less) of dilute Hydrofluoric Acid solution is spilled, clean it up by absorbing spilled material with the supplies in the Chemical Response Kit, and apply neutralizer to decontaminate surfaces. In some instances, powdered calcium carbonate or calcium hydroxide may be used to neutralize spilled material. If a larger amount is spilled, or if the acid is concentrated, contain the spill as best as you can use supplies in the Chemical Response Kit, evacuate the area, and call 911. Avoid exposure to the vapors.

(h) Dispose of unwanted hydrofluoric acid or spill cleanup materials by submitting online waste pickup requests.

(i) When working with Hydrofluoric Acid or concentrated HF solutions (> 1%):
1. Work in a fume hood with the sash as low as possible.
2. Wear PPE as defined above.
3. Wear a long-sleeved, buttoned lab coat, pants or long skirt, and closed-toe shoes.
4. Wear thick Neoprene or Nitrile gloves or HF-resistant gloves.
5. The Lab Supervisor/PI must be notified before any work with hydrofluoric acid occurs outside the chemical fume hood.

(j) Any exposure to Hydrofluoric Acid must be medically evaluated.

 
     

D. Further reading

1. MSDS for hydrofluoric acid: http://www.jtbaker.com/msds/englishhtml/H3994.htm

2. The following well written and useful SOP from the University of Maryland was consulted during the construction of this document::http://www.des.umd.edu/ls/sop/HydrofluoricAcid.pdf

3. Wikipedia entry on hydrofluoric acid safety: http://en.wikipedia.org/wiki/Hydrofluoric_acid#Safety

 
   
This chemical safety advisory document was prepared solely for the use of researchers affiliated to Oregon State University. As stated above (Section A), the content is designed to inform on good working practices and it is not intended to replace hands-on practical training in the techniques described. It is the responsibility of the Principal Investigator to see to it that his/her co-workers are properly trained and informed on hazard management, including the possibility of customization of the information herein as appropriate to meet specific needs. Neither Oregon State University, nor any of its employees (including the author), makes any warranty, express of implied, or assumes any legal liability or responsibility for the accuracy, completeness, or usefulness of any information, or represents that its use would not infringe privately owned rights. Reference herein to any specific commerical product, process, or service by trade name, trademark, manufacturer, or otherwise, does not necessarily constitute or imply its endorsement, recommendation, or favoring by Oregon State University.