UNSW Occupational Health and Safety Unit With special thanks to:

Working Safely With Hydrofluoric Acid (HF)

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Course Outline

• Properties of HF • Hazards Associated with HF • PPE required for HF use • Handling and Storage • Waste disposal• Emergency procedures

– Spills – Incidents– First Aid

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Properties of HF

What is Hydrofluoric Acid? • Colorless liquid with strong irritating odor

– Pungent odor at <1parts per million (ppm) - warning property

– Irritation to nose and throat at 3ppm

– Peak limit no more 3ppm for 15 minutes

• Non-flammable, very soluble in water • Vapor density = 0.7 (air = 1)

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Uses

• Mineral Digestion• Surface Activation (Si)• Silica Digestion • Plastics Production • Etching Glass, metals (Ti, Al)• Electronic Circuit Cleaners • Production & Purification of Radioactive Materials• May also be found in household rust removers, aluminium

cleaners and etching solutions.

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HF properties - Hazards

• Hydrofluoric Acid (HF) is one of the most corrosive of the inorganic acids and requires special safety precautions when using this chemical.

• HF acid burns are a unique medical problem. • Dilute solutions will deeply penetrate before

dissociating, – causing delayed injury and symptoms.

– Burns to the fingers and nail beds may leave the overlying nails intact.

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HF Properties – Medical hazards

• High concentrations on contact produces immediate necrosis and pain

• Delayed health effects occur at low concentrations. • Local effects include tissue destruction and necrosis. Burns may

involve underlying bone. • Serious Systemic Poisoning from severe burns includes:

– Hypocalcemia (low Calcium levels) – Hyperkalemia (High Potassium levels) – Hypomagnesemia (low magnesium levels) – Sudden death.

• Deaths have been reported from concentrated acid burns to as little as 2.5% Body Surface Area (BSA). (Palm of hand = 1%)

• Amputations have occurred from the exposure of fumes of a 2% solution. (LCLo = 50ppm/30mins inhalation)

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HF Classification – cut offs and labels

• Hydrofluoric Acid (7% and over)– T+, Very Toxic, C, Corrosive– R26/27/28, R35– Very toxic by inhalation, skin contact or swallowed,

causes severe burns• >=1% but less than 7%

– T, Toxic, R23/24/25, R34, C, Corrosive• >=0.1% but less than 1%

– Xn, Harmful, R20/21/22, R36/37/38– Harmful by inhalation, skin contact or swallowed,

Irritating to eyes, respiratory system, skin.• S(1/2) - 7/9 – 26 - 36/37 - 45

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Exposure types & routes

Direct exposure – Liquid exposure– Gas/Vapour exposure

Through:• Skin • Respiratory Tract • Eyes • Ingestion (rare)

Most HF exposures occur through inhalation of the gas/vapour or dermal contact

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SKIN

• HF is readily absorbed through the skin (osmosis) and deep tissue penetration occurs.

• HF binds to the calcium and magnesium in the body.

• Important to note that the surface area of burn is not predictive of end effects.

The 2 mechanisms that cause tissue damage are: –corrosive burn from the free hydrogen ions –chemical burn from tissue penetration of the

fluoride ions

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Skin pathophysiology

What occurs:• Fluoride ions penetrate and form insoluble salts

with calcium and magnesium. • Soluble salts also are formed with other

elements but dissociate rapidly. • Fluoride ions from this process release, and

further tissue destruction occurs.

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Skin pathophysiology

•The initial extent of the burn depends on the concentration, temperature, duration of contact, and quantity

Concentration Time to onset of symptoms

14.5% Immediately

12.0% Up to 1 hour

7% or less Several hours*

* It may take several hours before onset of symptoms, resulting in delayed presentation, deeper penetration of the un-dissociated HF, and a higher severity of burn.

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BURNS

Weaker solutions penetrate before dissociating. • Surface symptoms in these cases is minimal and may

even be absent. • Three categories (grades) of appearance:

– 1. white burn mark &/or erythema and pain– 2. white burn mark &/or erythema and pain, oedema &

blistering – 3. as above plus necrosis

• Ocular burns present with severe pain. • Inhalation burns may develop acute pulmonary oedema.

• Erythema is the superficial reddening of the skin• Oedema is a condition characterised by excess watery

fluid collecting in the cavities or tissue

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HF Facts

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BURNS

• Concentrated solutions cause immediate pain and produce a surface burn similar to other common acids with erythema, blistering and necrosis.

• The pain is typically described as deep, burning, or throbbing and is often out of proportion to apparent skin involvement.

• HF penetrates fingernails burning the pulp beneath without destroying the nails. Adequate treatment of these cases requires removal of the nails and/or intravenous and/or intra-arterial infusion of Calcium gluconate.

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EYES

• The eyes can be severely damaged from either vapor or liquid contamination

• Complications of eye exposure include corneal opacification, corneal sloughing, necrosis of the anterior chamber and keratoconjunctivitis.

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Inhalation

• HF is a volatile liquid with a b.p. of 112 C (40%).• Similar volatility to 30% HCl or acetic acid. • Its volatility makes it a high risk compound for

inhalation injury. Severity can range from mild airway irritation to severe burning and dyspnea (air hunger).

• With inhalation of HF concentrations > 50% there is a significant risk that they will develop pulmonary oedema/ARDS and pulmonary hemorrhage.

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Inhalation

Acute inhalation exposure symptoms include: – chills

– fever

– tight chest

– coughing

– choking

– bluish coloured lips and fingernails

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Ingestion

Generally from• Poor lab practices coupled with • inadequate personal hygiene after chemical use. • Ensure hands are washed even if you double

glove

Prognosis– Varies depending on severity of burn and site

of burn.

– The prognosis following HF inhalation is poor.

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Before Use in your Project

• Read MSDS – ChemAlert and/or manufacturer.• Perform risk assessment on tasks using HF

– Identify Hazards, assess & control Risks

• Develop Safe Working Procedures (SWP’s) or familiarise yourself with existing instructions

• Understand Laboratory protocols• Only use in applications you are authorised to do• Undergraduate classes MUST never use

Hydrofluoric Acid solutions.

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Personal Protective Equipment (PPE)

Always: – Use approved splash goggles

– Use full face shields

– Long Gloves (double glove) that cover wrist

– Use Neoprene, nitrile, latex

– Check the breakthrough time for the type of glove

– Safety glasses give NO splash protection

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Safe handling

Where possible:• Substitute for less hazardous substance • Use the most dilute HF solution practicable • Experienced staff should prepare the dilutions for learners.• Neutralise waste product immediately (lime in Na2CO3 sol’n)ALWAYS • Work in a chemical fume hood at least 200mm from the

edge • Use good housekeeping and laboratory practices.• Have a second person in the lab when you are using HF

(Buddy System) in full PPE

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Safe handling

Always• use a bottle carrier when transporting HF (never

transport open containers) • check your spill/exposure kit contents and

location before you start working • check expiration date of the calcium gluconate

BEFORE you start procedure

NEVER • use in a squirt bottle

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Spillage

Contain and Absorb• Check yourself for contamination• Use proprietary spill absorbent like Chemizorb which

absorbs and neutralises HF OR• Use other non Silicon based absorbent and neutralise

with lime (CaO) in sodium carbonate solution• OR slowly add NaHCO2, calcium hydroxide or calcium

carbonate solid to neutralise to pH7• Wear reusable gloves, face shield, apron and boots• Consider the need for evacuation and respirators

NEVER • Attempt to clean up large spills (>100mL)

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Storage

Always:• use secondary containment (spill containment)• store away from glass containers and incompatibles

(consult dangerous goods guidelines)– ammonia – bases – flammables and combustibles

• store in acid resistant cabinet below eye level • Replace cap when not in use • HF molecules will migrate through the bottle and disperse

harmlessly – do not store in a plastic bag

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Safe use

Never use Hydrofluoric Acid when working alone or after hours (when?).

• The buddy system must be implemented whenever using HF. All those working with or around HF must have HF training before commencing any work.

• HF may only be used in an approved laboratory. • Before beginning any procedure involving Hydrofluoric

Acid, make sure the access to the spill kit, emergency shower and eyewash is unobstructed.

• Have a supply of Calcium Gluconate Gel at home for delayed onset pains from unnoticed exposures

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EMERGENCY RESPONSE

For All Exposures (Incl. possible and combined with other chemicals)

• Do not panic• Activate buddy system response immediately:

(there should always be a second person in the lab when you are using HF)– Buddy to avoid becoming contaminated

• Wash area thoroughly with water for 5 minutes• Apply Calcium gluconate gel without hesitation• Obtain MSDS and phone security service X56666

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EMERGENCY RESPONSE

Procedure for Skin Exposure: • Help individual to eyewash/safety shower:

– Do not contaminate yourself; use PPCE

• 5 minutes in the safety shower (time it)• Victim should remove all contaminated items to remove

trapped HF (i.e. clothing, shoes and jewellery while under the shower and put in plastic bags for decontamination)

• Remove goggles last – face water stream and pull over head (front to back)

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EMERGENCY RESPONSE

Procedure for Skin Exposure (cont): • Buddy should bag all contaminated clothing and supplies

(USE PPE) • After 5 minutes washing - Victim should self administer

calcium gluconate: – Gentle continuous massaging in of the gel.

• if the victim is unable to administer, the buddy can assist using the disposable latex or nitrile gloves

• NOTE THE TIME OF INITIAL APPLICATION • (apply every 15 mins until medical help is present)

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EMERGENCY RESPONSE

Procedure for Eye Exposure: • Help individual to eyewash:

– Do not contaminate yourself; use PPCE

• 15 minutes in the eyewash OR• 5 mins in the eyewash (time it)

– Irrigate eye repeatedly via syringe with sterile 1% solution of calcium gluconate (not gel).

• Ice water compress may be applied to the eyes during transport to hospital for pain relief.

• Avoid rubbing the eyes.• Apply the 2.5% gel to any exposed parts of the face.

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EMERGENCY RESPONSE

Procedure for Inhalation Exposure: • Help individual to fresh air• Call X56666, request ambulance.• Keep the victim warm, quiet and comfortable.• If breathing stops, perform EAR.• Oxygen should be administered ASAP by a

trained individual until medical help arrives.• No other first aid treatment is possible.

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EMERGENCY RESPONSE

General Notes: • The responding person or assisting lab personnel must

remain with victim until ambulance arrives. • A copy of the MSDS, the calcium gluconate gel and the

emergency procedures must be also taken to the hospital. The doctors will thank you.

• It must be stressed to ALL medical professionals (doctors, ambos, nurses) that it is not an “ordinary” acid burn, it is HF and it is potentially Life Threatening.

• Look for other burn sites on the victim once treatment has begun.

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Waste Disposal Procedures

Waste Disposal Procedures – Regardless of the concentration of HF, it may not be

put down the drain. It may also not be neutralized and put down the drain.

• Neutralise all waste – e.g. calcium hydroxide• Collect neutralised waste HF in a clearly labelled,

appropriate container with a screw cap. • Glass and metal containers are unsuitable. • Where possible do not mix different acids together. • Complete chemical waste disposal form for removal

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Confidence using HF

• If you are uncomfortable using HF– Arrange for someone to undertake experiment on your

behalf

– Never use any HF solution on your own

– Only use HF solutions during office hours

• Ensure all safety equipment is checked and operational before use.

• No matter what the actual concentration of HF always:– use safety equipment provided

– treat it as though you are using full concentration

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