Hydrofluoric Acid Dangers
Hydrofluoric acid (HF) is primarily used for industrial applications. Stainless steel manufacturing, finishing metal, aluminum manufacturing, inorganic and organic chemical manufacturing, petroleum refining, mineral processing, glassmaking, and electronic components manufacturing mostly use this raw material. It is also found in certain industrial and consumer cleaning compounds. The use of HF in consumer products is discouraged because of its potential toxicity and the appropriate PPE and treatment should be present in areas where there is hydrofluoric acid (HF).
As a result of the fluoride ion, hydrofluoric acid (CAS # 7664-39-3) has an aggressive physiological reaction. The anhydrous form of hydrofluoric acid (hydrogen fluoride) and its solutions are both clear, colorless liquids. The vapors produced by concentrated solutions and anhydrous HF acid are especially dangerous when they are exposed to the air. It is imperative to prevent exposure to HF at all costs. In the event that exposure does occur, it is recommended that the specialized procedure that follows be followed to avoid the very serious consequences that might otherwise result.
Permissible Exposure Limit (PEL) and Skin Contact
The permissible Exposure Limit (PEL) is set by OSHA and it is measured as time-weighted average exposure for 8 hours of 3 ppm while NIOSH has established the level that is immediately dangerous to life and health (IDLH) at 30 ppm. Some of the available guides for responding to emergencies due to Hydrofluoric acid can be found in the manual providing a guideline by The American Industrial Hygiene Association (AIHA). Avoiding contact with the skin is very important. Skin burns caused by HF can be painful and serious. There is a need for specialized first aid and medical treatment. Burns larger than 25 square inches (160 square cm) may result in serious systemic toxicity. The acid from HF is very and it can severely burn skin, eyes, and mucous membranes. The vapors from anhydrous HF acid or its concentrated solutions can also burn these tissues. What makes hydrofluoric acid so dangerous is that the fluoride ion easily penetrates the skin, causing it to go deep inside the tissue layers. Unlike other acids which are rapidly neutralized, this process may continue for days if left untreated. If skin burns are not enough, severe throbbing pain due to irritation of nerve endings also is present. If slight diluted HF contact to the skin is present, redness, edema, and blistering will appear where more concentrated HF acids, and a blanched white area appears. When treating such exposure to HF, dealing with it in a quick manner is essential. Not adhering to this can result in great damage and in some cases, fatality. The main issue is to bind the fluoride ions from HF to prevent tissue damage. This can be done by treating the affected area with a soaking agent that has a high molecular weight quaternary ammonium compounds, like benzalkonium chloride. Calcium gluconate gel can be applied locally, and calcium gluconate solution may be injected (subcutaneously, intravenously, or intra-arterially) or used as an irrigant.
When dealing with the exposure it is important to call medical personal and follow these steps before they arrive.
1.Move the victim immediately under a safety shower and flush the affected area thoroughly with large amounts of running water.
2.It is important to be fast and thorough in washing off the acid. Flush the affected areas even before removing any articles of clothing.
3. While flushing with water under a safety shower, be prepared to dispose and remove all contaminated clothing. If the exposure is limited to HF and other water-soluble substances, 5 minutes of water decontamination after the removal of all PPE, clothing, and jewelry should be sufficient.
4. Concomitant exposure with hydrocarbons or other substances with limited water solubility may require longer water decontamination or the use of other decontaminating agents. If a more definitive treatment (0.13% benzalkonium chloride solution or 2.5% calcium gluconate) is not available, water irrigation should continue until one of these agents is available or transportation to a medical facility is initiated.
5. After washing begin soaking the affected areas in iced 0.13% benzalkonium chloride solution. Use ice cubes, not shaved ice, to prevent frostbite. The compresses soaks should be changed every 2 to 4 minutes. Do not use benzalkonium chloride solution for irrigation of the eyes. Exercise caution when using benzalkonium chloride solution near the eyes as it is an eye irritant. Benzalkonium chloride soaks or compresses should be continued until pain is relieved or until more definitive medical treatment is provided.
6. Start applying 2.5% calcium gluconate gel into the burn site. Apply frequently and continuously until pain and/or redness disappear or until more definitive medical care is given. The individual applying the calcium gluconate gel should wear disposable surgical gloves to prevent a secondary HF burn.
7. Make sure the victim is examined to ensure there are no other burn sites which have been overlooked.
8. Arrange to have the victim seen by a physician. If the victim has to be transported to medical facility, it is very important to continue the first aid care, whether with benzalkonium chloride or massaging calcium gluconate gel. In many situations, particularly for minor burns covering a small skin area or for burns caused by dilute HF, continued treatment with soaks. All persons with extensive burns or burns with significant blister formation or with the appearance of whitish or dead skin need to be seen by a physician. All persons with HF burns which do not respond to either calcium gluconate gel or benzalkonium chloride soaks or compresses within 30 minutes should be evaluated by a physician.
The toxicity levels of HF acid is very serious. Personal protection equipment (PPE) should specific for each individual operations. Some of the safety products available tolab workers include all or some of the following but all are needed for etching operations.
- Neoprene gloves
- Coated coveralls - Tyvek or similar
- Rubber aprons and knee-boots
- A face shield
The face shield and visor should be splash acid resistant with a visor that covers below the chin area. Neoprene gloves are capable of resisting HF acid for about eight hours. You can also wear surgical gloves underneath as a secondary form of protection or as liners although these gloves do not provide any protection on their own. Protective boots should be worn on top of normal shoes. A full body suit like Tyvek or Tychem should be worn at all times when working in direct areas where acids are present. While these safety items are important and serve as immediate protection, nothing is better than proper training and planning. Make sure to have designated areas posted with operating procedures for toxic emergencies and the proper PPE in all stations. Work in pairs and never alone. If an accident happens help the affected individual to eyewash/safety flush shower area and flush with large amounts of water for 5 minutes.and have the employee remove all contaminated clothing while under the shower. Call emergency services while applying the appropriate neutralizing agents until emergency personnel comes.