Properties of HF

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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 lt 1ppm Vapour density 2.21_at_ 21oC (air
1) Vapour Pressure (mmHg) 776 _at_ 21oC
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Irritation to nose and throat at 3ppm
Permissable 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
In ICS Microchip and substrate etching Glass
etching and cleaning In ELS Digestion of
geological materials Glass etching
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
hypocalcemia or hyperkalemia must not handle of
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 Victim
s 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
gt 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
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.
Relief of pain is an important guide to success
of treatment.
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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 gt 50 there is a significant risk
that they will develop pulmonary edema/ARDS and
pulmonary hemorrhage.
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Inhalation
Acute inhalation exposure symptons
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
• Ensure you get appropriate PPE to protect
  yourself.
• 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.
• Buddy should bag all contaminated clothing and
  supplies (use PPE)

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Emergency Response

• Procedure for Skin Exposure
• 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 APPLICATION
• May need to apply every 20 minutes until the
  pain subsides or reaches the hospital
• Take 6 calcium carbonate tablets (TUMS) if
  conscious
• Inform Emergency Medical Personnel that calcium
  carbonate and calcium gluconate have been
  administered.

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Emergency Response

• Procedure for Eye Exposure
• Use eyewash for 15 minutes holding lid open
  (upper and lower) for irrigation and wait for
  emergency response personnel.
• Conduct this process for both liquid or vapour
  contamination.
• Take 6 calcium carbonate tablets (TUMS) if
  conscious.
• Inform Emergency Medical Personnel that calcium
  carbonate was administered.

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Emergency Response

• Procedure for Inhalation Exposure
• Immediately remove the victim to clean air if it
  is safe to do so.
• The victim should ingest 6 calcium carbonate
  tablets if conscious and wait for emergency
  medical response.
• Inform Emergency Medical Personnel that calcium
  carbonate has been administered.

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Emergency Response

• General Notes
• The responding person or assisting lab personnel
  must escort the victim to the hospital.
• 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 (gt10 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 gt50 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 (xxxx)
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.