UNSW Occupational Health and Safety Unit
With special thanks to:
Working Safely With Hydrofluoric Acid (HF)
Course Outline
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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
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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:
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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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