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Working Safely With Hydrofluoric Acid

• Properties of HF• Hazards Associated with HF• Handling and Storage• Proper PPE• Spills and Accidents• Incident Response Procedure• Using HF at Macquarie University

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What is Hydrofluoric Acid?

• 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.

• Nonflammable, very soluble in water• Boiling point of 19.5oC with strong pungent

and irritating odor– Pungent odor at < 1ppm– Vapour density = 2.21@ 21oC (air = 1)– Vapour Pressure (mmHg) 776 @ 21oC

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Irritation to nose and throat at 3ppm

• Permissible Exposure Limit (PEL) set by US Occupational Safety and Health Administration (OSHA)

• = 3ppm averaged over an 8 hour shift

• OSHA Short term exposure limit (STEL)• = 6ppm averaged over 15 minutes

• US National Institute for Occupational Safety and Health (NIOSH) established the level that is immediately Dangerous to Health (IDH)

• = 30ppm

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Irritation to nose and throat at 3ppm

• The American Industrial Hygiene Association has published an Emergency Response Planning Guideline setting:

• 50ppm as the maximum exposure level for 1 hour without experiencing or developing life threatening health effects.

• 20ppm as the maximum exposure level for 1 hour without developing irreversible health effects or symptoms

• 2ppm as the maximum exposure level for 1 hour without experiencing other than mild transient adverse health effects

• HF MUST ONLY BE USED IN AN APPROPRIATE FUME CABINET

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Uses of HF at Macquarie

• Microchip and substrate etching• Glass etching and cleaning• Digestion of geological materials• Chromatographic separations and

cleaning (diluted solutions)

In general, use of HF is discouraged because of its toxicity

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Hazards Associated with HF

Hydrofluoric Acid (HF) is one of the strongest and most corrosive of the inorganic acids. Therefore special

safety precautions are necessary when using this chemical.

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HF burns pose a unique medical problem• Dilute solutions deeply

penetrate before dissociating, thus causing delayed injury and symptoms. Burns to the fingers and nail beds may leave the overlying nails intact.

• Because medical treatment of HF is so specialised and different from the treatment of other inorganic acid exposures physicians may be unaware of appropriate treatment measures.

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Hazards

• On contact with live tissue, HF produces immediate necrosis and pain at high concentrations

• HF is a Serious Systemic Poison

• Delayed health effects at low concentrations

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Morbidity/Mortality

• Local effects include tissue destruction and necrosis.

• Burns may also involve underlying bone.• Systemic fluoride ion poisoning from severe

burns is associated with:– Hypocalcemia (low Calcium levels)– Hyperkalemia (low Potassium levels)– Hypomagnesemia (low Magnesium levels)– Sudden death (heart arrhythmias)

• Deaths have been reported from concentrated HF acid burns to as little as 2.5% Body Surface Area (BSA)

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Morbidity/Mortality

People who take medication or who have a history of intercurrent illness that

predisposes them to hypocalcaemia or hypercalcemia must not handle or use

HF.

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Exposure Types

• Direct exposure• Liquid exposure (skin, eye, ingestion)• Gas/vapour exposure (inhalation, skin and eyes)

• Indirect or secondary exposure• Victims exposed to HF vapours only do not pose a

significant risk of secondary contamination• Victims whose clothing or skin is contaminated

with HF liquid or solution can potentially contaminate response personnel by direct contact or off-gassing vapours

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Routes of Exposure

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

• Most HF exposures occur by:• Inhalation of the gas/vapour• Dermal contact (in particular through

gloves)

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Skin

• HF is readily absorbed through the skin and deep tissue penetration by the fluoride ion ensues.

• The fluoride ion binds to the calcium and magnesium in the body.

• The surface area of the burn is not a predictor nor indicator of effects

Unlike other acids which are rapidly neutralised, the effects of HF may continue for days if left unattended.

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Skin Pathophysiology

• The 2 mechanisms that cause tissue damage are:

• Corrosive burns from the free hydrogen ions• Chemical burn from tissue penetration of the fluoride

ions

• Fluoride ions penetrate and form insoluble salts with calcium and magnesium. Soluble salts also are formed with other cations but dissociate rapidly. Consequently, fluoride ions 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

> 50% Immediately

20 - 50% 1 - 8 hours

20% or less Up to 24 hours*

* may take several hours before the onset of symptoms, resulting in delayed presentation, deeper penetration of the un-associated HF, and a more severe burn.

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Burns

Relief of pain is an important guide to success of treatment.

• 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 intr-arterial infusion of calcium gluconate.

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Burns• Weaker solutions penetrate before

dissociating.• Surface involvement in these cases is

minimal and may even be absent.

• Three categories of appearance:• A white mark and/or erythema and pain• A white burn mark and/or erythema and

pain, plus edema and blistering• Ocular burns present with severe pain

• Inhalation burns may develop acute pulmonary edema.

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Eyes• The eyes can be severely

damaged from either vapour or liquid contamination.

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

• May present with severe pain.

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Inhalation

• HF is a volatile liquid with a boiling point of only 19.5oC.

• Its volatility makes it a high risk compound for inhalation injury. Severity can range from mild airway irritation to severe burning and dyspnea.

• With inhalation of HF concentrations > 50% there is a significant risk that they will develop pulmonary edema/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

Poor laboratory practices coupled with inadequate personal hygiene after

chemical use is the most common route for ingestion exposure.

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Ingestion - prognosis

• Ingestion of HF may result in severe burns to the mouth, aesophagus and stomach.

• Severe systemic effects are common.• Effects varies depending on the severity

of the burn and site of burn.• The prognosis following HF inhalation is

poor.• Ingestion of even small amounts of dilute

HF have resulted in death.

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Safe Handling

• Substitute for less hazardous substance whenever possible

• Use the most dilute HF solution practicable• ALWAYS work in an appropriate acids chemical

fume hood (with scrubber)• Ensure the chemical fume hood is operating

properly• Ensure all work is at least 15 cm from the edge

of the bench• Good housekeeping (clean up)• LABEL LABEL LABEL• Always use proper PPE

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Safe Handling• Implement a buddy system and never work

with HF alone• Order and keep on hand the minimum quantity

possible• Cap when not in use (even during your work

procedure)• Undertake a risk assessment of all procedures• Use a bottle carrier when transporting HF (no

open containers)• Check your spill/exposure kit contents and

location before you start working• Check the expiration data of the calcium

gluconate BEFORE you start your procedure

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Personal Protection

• Eyes– Contact lenses may not be worn when

handling HF. – Splash-proof chemical goggles or safety

glasses with side shields are required. Face shields must be worn during HF use.

• Protective Clothing– A lab coat, in addition to long gauntlet-

type gloves, is the minimum suggested protection for small quantities of HF (i.e., a few ml). Neoprene aprons with attached sleeves should be worn while transferring quantities in excess of 10 ml of HF

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Personal Protection• Gloves• Even pin-hole leaks through gloves may result

in significant damage to the skin, especially if contact under the finger nails occurs. If hands are sweaty, leakage may not even be noticed. Gloves should be dedicated for HF use only, and should be discarded if any contact with the acid occurs. They should be inspected prior to use and changed frequently.

• Glove breakthrough times vary with material, thickness and manufacturer. Contact the glove manufacturer or EMS for information on specific gloves. In general, long gauntlet-type nitrile, neoprene, and natural rubber gloves should provide adequate protection against splashing and during the clean-up of small hydrofluoric acid spills.

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Storage

• ALWAYS use secondary confinement.• Store away from incompatibilities

– Ammonia, bases, flammables and combustibles

• Store in an acid resistant cabinet and liner (with secondary confinement)

• ALWAYS store below eye level• ALWAYS cap when not in use• NEVER use a squirt bottle

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Emergency Response

• General Procedure for ALL EXPOSURES• Do not panic!• Activate a buddy system response

immediately:• The buddy should call SECURITY on

9999 or 7112 immediately and tell them:

– You have a Hydrofluoric acid exposure– Your exact location and contact details– Need to send an ambulance immediately

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Emergency Response

Procedure for Skin Exposure:1. Ensure you get appropriate PPE to protect

yourself.

2. Help the individual to eyewash/safety shower:– Wash victim for 1 – 5 minutes under the safety

shower– Victim should remove all contaminated items (ie

clothing, shoes and jewelry) while under the shower– Remove goggles last.

3. Buddy should bag all contaminated clothing and supplies (use PPE)

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Emergency Response

Procedure for Skin Exposure:4. Victim should self administer calcium

gluconate:If the victim is unable to administer, the buddy should assist using appropriate PPE.

NOTE THE TIME OF THE INITIAL APPLICATIONMay need to apply every 20 minutes until

the pain subsides or reaches the hospital5. Take 6 calcium carbonate tablets (TUMS) if

conscious6. Inform Emergency Medical Personnel that

calcium carbonate and calcium gluconate have been administered.

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Emergency Response

Procedure for Eye Exposure:1. Use eyewash for 15 minutes – holding lid

open (upper and lower) for irrigation and wait for emergency response personnel.

2. Conduct this process for both liquid or vapour contamination.

3. Take 6 calcium carbonate tablets (TUMS) if conscious.

4. Inform Emergency Medical Personnel that calcium carbonate was administered.

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Emergency Response

Procedure for Inhalation Exposure:1. Immediately remove the victim to

clean air if it is safe to do so.2. The victim should ingest 6 calcium

carbonate tablets if conscious and wait for emergency medical response.

3. Inform Emergency Medical Personnel that calcium carbonate has been administered.

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Emergency Response

General Notes:1. The responding person or assisting lab

personnel must escort the victim to the hospital.

2. A copy of the MSDS, the calcium carbonate tablets, the calcium gluconate gel, a copy of the Honeywell HF Medical Treatment Brochure and these emergency procedures must also be taken to the hospital.

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Spills

General Procedure for ALL HF SPILLS:• Refer to the product Material Safety Data Sheet

for proper spill clean-up procedures. Do not attempt to clean up any large spills, especially if the vapors from the spill result in noticeable eye or respiratory irritation. For large spills (>10 ml) restrict access to the spill area and dial 9999.

• Small spills of a few ml may be cleaned up by the person who caused the spill.

• Do not attempt to clean up any spills without appropriate PPE (gloves, an apron, eye, and face protection). Use of an appropriate respirator if the HF concentration of the spilled material is >50% is mandatory.

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Spills• If there is any possibility of contamination of

footwear while cleaning up the spill, do not proceed unless adequate shoe coverings or rubber boots can be obtained.

• Absorb the spill with lime or another absorbent material designated for HF spills. Scoop the material into a suitable container. Note that HF may react with metal to form hydrogen.

• Carefully rinse contaminated areas with water. Any paper towels or sponges used to absorb the rinse water should be added to the spill clean-up wastes.

• Label the waste container and contact the Safety Office (8169) for pick up of the spill clean-up materials.

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Safe Use of HF at Macquarie• Never use HF when working alone or after hours• The buddy system must be implemented

whenever HF is used.• Everyone working with or around HF must have HF

training before commencing work.• A sign should be posted to alert people that work

with HF is in progress.• Everyone working with HF must be properly

trained on the appropriate waste management procedure.

• An emergency response kit must be available in all laboratories where HF is stored or used.

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Safe Use of HF at Macquarie• The Emergency Response Kit must also include a copy of the

Honeywell HF Medical Treatment Brochure.

• A copy of the MSDS and all Risk Assessments must be located in the laboratory at the time of use.

• Before beginning any procedure involving HF check the access to the emergency shower and eyewash is unobstructed.

• Only experienced staff familiar with HF should handle the concentrated acid.

• Undergraduate students MUST NOT mix HF acid solutions.

• ANY exposure to HF must be medically evaluated and reported.

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Safe Use of HF at Macquarie

• NO HF work is to be conducted outside of a properly operating chemical fume hood.

• ALL HF work must be conducted in a secondary container insider the chemical fume hood.

• Work in the chemical fume hood with the sash as low as possible.

• WEAR PPE at all times.

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Waste Disposal Procedures

Regardless of the concentration of HF, it may not be put down the drain.