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Hazardous Substances Policy - Control Measures
UHSP/15/HS/05 Schedule 3.8.14
Enhanced Good Chemical Practice
for Work with Pyrophoric Substances
INTRODUCTION
Aims of the policy
Pyrophoric substances are extremely reactive and can ignite spontaneously on contact with air;
reacting with oxygen, moisture in the air or both. Failure to follow proper handling procedures can
result in fire or explosion leading to serious injuries/death or significant damage to facilities.
Pyrophoric chemicals are classified under the ‘Chemicals (Hazard Information and Packaging for
Supply) Regulations (CHIP) and ‘Classification, Labelling and Packaging of Substances and Mixtures
Regulations’ (CLP). Under the CHIP Regulations they are assigned the Risk Phrases R17
‘Spontaneously flammable in air’. Under the CLP Regulations they are assigned the Hazard Statement
H250 ‘Catches fire spontaneously if exposed to air’.
The Code of Practice and Appendices associated with this policy contains further information on the
safe working practices that must be adopted when handling pyrophoric liquids and solids. In addition
all those handling these reactive chemicals must be trained in their safe use and correct laboratory
technique by or under the supervision of a suitably experienced colleague assigned by their Principal
Investigator and be able to demonstrate proficiency.
Scope of the Policy
This policy applies to the use and storage of all pyrophoric substances in connection with University
activities.
POLICY
Heads of Budget Centres must make arrangements in areas under their control to ensure:

A Chemical Hazard and Risk Assessment must be completed for all tasks involving pyrophoric
substances.

All users must be trained in the hazards and safe use of pyrophoric substances by or under
the supervision of a suitably experienced colleague assigned by their Principal Investigator
and be able to demonstrate proficiency. A record of training must be kept.

Personal protective equipment must be worn whenever handling pyrophoric chemicals.

Pyrophoric chemicals must not be used outside normal working hours.
 The provisions within the Code of Practice must be observed.
 Appropriate emergency procedures must be in place for in the event of a spill.
1
PYROPHORIC LIQUIDS
A variety of liquid reagents are pyrophoric (spontaneously ignite in air) including (but not necessarily
limited to):

Alkyllithium reagents (Typically in hydrocarbon solvents) (Tert-butyllithium is VERY
pyrophoric).

Alkenyllithium and Aryllithium reagents (Typically in hydrocarbon solvents).

Alkynyllithium reagents (Typically in hydrocarbon solvents).

Grignard Reagents (RMgX) (Typically in hydrocarbon solvents).

Alkylaluminum reagents (Neat or in hydrocarbon solvents) (Neat reagents are VERY
pyrophoric).

Alkylzinc reagents (Neat reagents are pyrophoric).

Boranes (Neat reagents are pyrophoric).
PRINCIPAL CONTROL MEASURES
Engineering Controls
Many pyrophoric chemicals release noxious or flammable gases and therefore must always be
handled in a ducted fume cupboard, with the sash at the lowest practicable working height. In addition,
some pyrophoric materials are stored under kerosene (or other flammable solvent), therefore the use
of a fume cupboard is required to prevent the release of flammable vapours into the laboratory.
A glove box should be used where inert or dry atmospheres are required for handling pyrophorics.
Glove
bags
may
provide
a
cheaper
alternative,
such
as
Sigma’s
Atmosbag
(http://www.sigmaaldrich.com/labware/products/aldrich-atmosbag.html)
Manipulation of pyrophoric liquids must be conducted via a cannula or syringe transfer to prevent
exposure to air if not handled within an inert atmosphere (see Appendix 1 for further information).
Syringes;
Simple glass syringes are more prone to causing gas bubbles. Disposable plastic syringes have a
good seal on the plunger and work well. Glass syringes with Teflon-tipped plungers (gastight) syringes
are generally regarded as the best.

A syringe must never be filled to its maximum capacity.

The quantity transferred must not exceed 60% of the maximum syringe capacity.

Syringe transfers should not be used for quantities greater than 12ml.

Needles should be equipped with a locking mechanism to prevent accidental disconnection
and release of substance.

Plastic syringes must not be reused for multiple transfers in order to prevent swelling.

Plastic syringes should be checked for compatibility with the reagents being used.
Administrative Controls
A Chemical Hazard and Risk Assessment must be completed for all tasks involving pyrophoric
substances.
All users must be trained in the hazards and safe use of pyrophoric substances by or under the
supervision of a suitably experienced colleague assigned by their Principal Investigator and be able to
demonstrate proficiency. A record of training must be kept.
Pyrophoric chemicals must not be handled outside normal working hours.
The quantities of pyrophoric reagents purchased and stored should be minimised. Use the smallest
quantity of material practical.
Pyrophoric chemicals should only be handled in a designated work area - a laboratory, bench or fume
cupboard that has been appropriately set-up and cleared of any other flammable materials other than
those present for the transfer/reaction process. The area should be clearly identified whilst work is
2
taking place. All pyrophoric materials must be removed and the area cleaned before it is returned to
general laboratory use and signage removed.
Personal Protective Equipment (PPE)
At a minimum, gloves, safety glasses and lab coat must be worn
Eye Protection

Chemical goggles or safety glasses that meet BSEN166 must be worn whenever handling
pyrophoric chemicals. When there is a potential for splashing goggles must worn or a face
shield where appropriate.

A face shield is required when there is a risk of explosion, large splash hazard, or a highly
exothermic reaction. All procedures involving pyrophoric chemicals which pose this risk should
be carried out in a fume cupboard with the sash in the lowest practicable position.
Skin Protection

Gloves must be worn whenever handling pyrophoric chemicals. Nitrile gloves should be
adequate for the majority of occasions, but they are combustible. Heavier gloves, such as
Nomex, should be worn when working with large quantities.

A laboratory coat must be worn at all times when handling pyrophoric substances.

Synthetic clothing is strongly discouraged when handling pyrophoric substances.
Storage
Only the smallest quantity of material practicable should be used and stored
Store pyrophoric chemicals under an inert atmosphere or under kerosene as appropriate.
Avoid storing in areas with heat/flames, corrosives, oxidizers, and water sources.
Pyrophoric substances should not be stored with flammable, corrosive or oxidising substances
All containers must be clearly labelled with the correct chemical name and hazard warning.
Never return excess chemical to the original container. Small amounts of impurities introduced to the
container may cause a fire or explosion.
EMERGENCIES
Spills
Exert caution due to potential spontaneous combustion and potential ignition of flammable solvents or
other materials in the area.
Wear gloves, lab coat and eye goggles or face shield.
Eliminate all sources of ignition
Cover the spill with a mixture (1:1:1) of sodium or calcium carbonate, bentonite (clay cat litter) and
sand.
Transfer to a container and place in a fume cupboard.
Deactivate or allow to evaporate.
Further information on the treatment of spillages of individual pyrophoric substances can be found in
Hazardous Laboratory Chemicals Disposal Guide by Margaret-Ann Armour. A copy is held by the Health and
Safety Unit.
In the event of a large spill the area should be evacuated.
Fire
DO NOT use water, CO2 or dry powder extinguishers to attempt to quench a fire involving pyrophoric
substances – this can greatly exacerbate the problem.
3
A specialist Class D powder extinguisher is required where pyrophoric substances are used. All those
involved in the handling of pyrophoric substances should be trained on the use of these specialist
extinguishers. Please contact the University Fire Safety Adviser for further information.
In the event of a small amount of material igniting, it should be extinguished with dry sand. A container
of sand or powdered lime (calcium oxide) should be kept within the immediate vicinity when working
with pyrophoric substances.
Fire extinguishers should be readily available for immediate use in the event of a fire.
If the container of material has ignited then evacuate the laboratory immediately. Activate the nearest
fire alarm call point and inform the School fire warden of the location of the incident and substance
involved.
SAFE SYSTEMS OF WORK WITH PYROPHORIC LIQUIDS
Pyrophoric reagents can be handled and stored safely as long as all exposure to atmospheric oxygen
and moisture is avoided. Finely divided solids must be transferred under an inert atmosphere in a
glove box or suitable alternative. Liquids may be safely transferred without the use of a glove box by
employing techniques and equipment such as those discussed in the Sigma Aldrich Technical
Information Bulletin AL-134.
http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Bulletin/al_techbull_al134.Par.0001.File.tmp/al
_techbull_al134.pdf
Transferring Pyrophoric Reagents with Syringe

In a fume hood or glove box, clamp the reagent bottle and receiving vessel to prevent them from
moving.

Insert a needle from an open inert gas line fitted with a bubbler (Be sure to have purged the line
before inserting into the reagent bottle). The inert gas flow rate must be sufficient to ensure a
positive pressure at all times during the transfer i.e. greater than the rate of syringe filling.
Carefully keep the tip of the needle above the level of the liquid.

After flushing the dry syringe with inert gas and carefully checking that the needles is securely
connected to the syringe, depress the plunger and insert the syringe into the Sure/Seal bottle with
the tip of the needle below the level of the liquid.

Position the syringe so if the plunger blows out of the body it, and the contents will not impact
anyone (aim it toward the back of the containment).

Either: Gently pull out the plunger from the syringe (do this in a way to ensure you do not pull the
whole syringe away from the reagent bottle). No bubbles should be observed in the syringe at this
rate. Excess reagent and entrained bubbles are then forced back into the reagent bottle as shown
in Fig. 2B.

Or: Use inert gas pressure as detailed in the Sigma Aldrich Technical Information Bulletin AL-134
to fill the syringe. This approach will require closing off the bubbler on the inert gas line and will
result in a more pressurised inert gas line. Extra caution should be adopted to ensure that the
gas pressure is not too high. Excess reagent and entrained bubbles are then pushed back into the
reagent bottle as shown in Fig. 2B.

FOR HIGHLY PYROPHORIC liquids such as tert-butyllithium and trimethylaluminum, it is best to
draw a plug of inert gas from the headspace into the needle after excess reagent is forced back
into the bottle and before withdrawing the needle.

The desired volume of reagent in the syringe is quickly transferred to the reaction apparatus by
puncturing a rubber septum as illustrated in Fig. 2C When using gas-tight syringes only a
protective layer of inert gas can be drawn into the syringe for transfer between vessels. Remove
the needle from the liquid keeping it in the reagent vessel. Up end the syringe so the needle is at
the top and withdraw a small amount of inert gas sufficient to empty the needle of any solution.
4
Dealing with Suspensions
When transferring from a bottle/flask containing an insoluble species care must be taken not to
draw up any undesired insoluble material into the syringe to avoid blocking the needle. In the
case of non-homogenous solutions only start syringing once the contents have settled. Place the
needle tip as far above the level of any sediment as possible and fill the syringe slowly to avoid
disturbing and taking up any insoluble material.
Transferring a suspension entirely, including insoluble material, must be avoided. In the rare
event that no alternative means to affect the required transfer can be safely employed, then
extreme care must be taken to avoid blocking the syringe needle. Wider bore needles must be
used and the material transferred in small quantities.
If a needle becomes blocked increased pressure MUST NEVER be applied to the plunger in an
attempt to clear.
Fig. 2A Filling syringe using nitrogen pressure
Fig. 2B Removing gas bubbles and returning excess reagent
to the Sure/Seal bottle
(Sigma-Aldrich Technical Bulletin Al-134)
(Sigma-Aldrich Technical Bulletin Al-134)
Fig. 2C Syringe transfer of reagent to reaction vessel
Fig. 3A Double-tipped needle transfer of liquid reagent
(Sigma-Aldrich Technical Bulletin Al-134)
(Sigma-Aldrich Technical Bulletin Al-134)
5
Transferring Pyrophoric Reagents with a Double-Tipped Needle (Cannula)

The double-tipped needle technique is recommended when transferring 50 mL or more.

Pressurize the Sure/Seal bottle with nitrogen and then insert the double-tipped needle through
the septum into the headspace above the reagent. Nitrogen will pass through the needle. Insert
the other end through the septum at the calibrated addition funnel on the reaction apparatus. Push
the needle into the liquid in the Sure/Seal reagent bottle and transfer the desired volume. Then
withdraw the needle to above the liquid level. Allow nitrogen to flush the needle. Remove the
needle first from the reaction apparatus and then from the reagent bottle (Fig. 3A).

For an exact measured transfer, convey from the Sure/Seal bottle to a dry nitrogen flushed
graduated cylinder fitted with a double-inlet adapter (Fig. 3B). Transfer the desired quantity and
then remove the needle from the Sure/Seal bottle and insert it through the septum on the reaction
apparatus. Apply nitrogen pressure as before and the measured quantity of reagent is added to
the reaction flask.

To control flow rate, fit a Luer lock syringe valve between two long needles as shown in (Fig. 3C).
Fig. 3B Double-tipped needle transfer to graduated cylinder
syringe valve
Fig. 3C Double-ended needle transfer with
(Sigma-Aldrich Technical Bulletin Al-134)
(Sigma-Aldrich Technical Bulletin Al-134)
Cleaning Pyrophoric Reagents from Needles and Syringes

The quenching method must be set-up prior to any manipulation of the pyrophoric material so
that there is no delay to the quenching process.

Needles and syringes used with pyrophoric reagents must be cleaned immediately to avoid
clogging the needles and seizing the syringes.

Draw hexane into the syringe containing small amounts of pyrophoric reagent and then discharge
the diluted solution into isopropanol.

Similarly, flush double-tipped needles with hexane and then quench hexane wash in isopropanol.
6
PYROPHORIC SOLIDS
A variety of solids are pyrophoric (spontaneously ignite in air) including (but not necessarily limited to):

Finely divided metals (bismuth, calcium, hafnium, iron, magnesium, titanium, uranium,
zirconium).

Alkali metals (lithium, sodium, potassium, especially sodium potassium alloy – NaK, and even
more dangerous are cesium and rubidium).

Low valent metals (titanium dichloride).

Nonmetals (white phosphorous).

Metal hydrides (potassium hydride, sodium hydride, lithium aluminium hydride, uranium.
trihydride).

Alkylated metal alkoxides or halides (dimethylaluminium chloride, diethylethoxyaluminium).

Metal carbonyls (dicobalt octacarbonyl, nickel carbonyl).

Used hydrogenation catalysts, e.g. Raney Ni, are especially hazardous due to adsorbed
hydrogen.

Copper fuel cell catalysts, e.g. Cu/ZnO/Al2O3 Methanetellurol (CH3TeH).

Finely divided Iron sulfides (FeS, FeS2, Fe3S4), Potassium sulfide (K2S), Aluminum
phosphide (AlP).
Principal Control Measures
Engineering Controls
Many pyrophoric chemicals release noxious or flammable gases and therefore must always be
handled in a ducted fume cupboard, with the sash at the lowest practicable working height. In addition,
some pyrophoric materials are stored under kerosene (or other flammable solvent), therefore the use
of a fume cupboard is required to prevent the release of flammable vapours into the laboratory.
Finely divided solids must be transferred under an inert atmosphere in a glove box or suitable
alternative. A glove box should be used where inert or dry atmospheres are required for handling
pyrophorics. Glove bags may provide a cheaper alternative, such as Sigma’s Atmosbag
(http://www.sigmaaldrich.com/labware/products/aldrich-atmosbag.html).
Administrative Controls
A Chemical Hazard and Risk Assessment must be completed for all tasks involving pyrophoric
substances.
All users must be trained in the hazards and safe use of pyrophoric substances by or under the
supervision of their Principal Investigator and be able to demonstrate proficiency. A record of training
must be kept.
Pyrophoric chemicals must not be handled outside normal working hours.
Pyrophoric chemicals must be used and stored under inert conditions or away from all other
flammable and combustible materials.
The quantities of pyrophoric reagents purchased and stored should be minimised. Use the smallest
quantity of material practical.
Pyrophoric chemicals should only be handled in a designated work area; a laboratory, bench, fume
cupboard or glove box that has been appropriately set-up and cleared of any other flammable
materials other than those present for the transfer/reaction process. The area should be clearly
identified whilst work is taking place. All pyrophoric materials must be removed and the area cleaned
before it is returned to general laboratory use and signage removed.
7
Personal Protective Equipment (PPE)
At a minimum, gloves, safety glasses and lab coat must be worn
Eye Protection

Chemical goggles or safety glasses that meet BSEN166 must be worn whenever handling
pyrophoric chemicals. A face shield is required when there is a risk of explosion, or a highly
exothermic reaction. All procedures involving pyrophoric chemicals which pose this risk should
be carried out in a fume cupboard with the sash in the lowest practicable position.
Skin Protection

Gloves must be worn whenever handling pyrophoric chemicals. Nitrile gloves should be
adequate for the majority of occasions, but they are combustible. Heavier gloves, such as
Nomex, should be worn when working with large quantities.

A laboratory coat must be worn at all times when handling pyrophoric substances.

Synthetic clothing is strongly discouraged when handling pyrophoric substances.
Storage
Only the smallest quantity of material practicable should be used and stored.
Pyrophoric chemicals must be used and stored under an inert atmosphere or away from other
flammable and combustible materials.
Avoid storing in areas with heat/flames, corrosives, oxidizers, and water sources.
All containers must be clearly labelled with the correct chemical name and hazard warning.
Solid pyrophoric substances should be stored under an inert atmosphere or under kerosene as
appropriate.
Never return excess chemical to the original container. Small amounts of impurities introduced to the
container may cause a fire or explosion.
Emergencies
Spills
Exert caution due to potential spontaneous combustion and potential ignition of flammable solvents or
other materials in the area.
Wear gloves, lab coat and eye goggles or face shield.
Eliminate all sources of ignition
Cover the spill with a mixture (1:1:1) of sodium or calcium carbonate, bentonite (clay cat litter) and
sand.
Transfer to a container and place in a fume cupboard.
Deactivate.
Further information on the treatment of spillages of individual pyrophoric substances can be found in
Hazardous Laboratory Chemicals Disposal Guide by Margaret-Ann Armour. A copy is held by the Health and
Safety Unit.
In the event of a large spill the area should be evacuated.
Fire
DO NOT use water, CO2 or dry powder extinguishers to attempt to quench a fire involving pyrophoric
substances – this can greatly exacerbate the problem.
A specialist Class D powder extinguisher is required where pyrophoric substances are used. All those
involved in the handling of pyrophoric substances should be trained on the use of these specialist
extinguishers. Please contact the University Fire Safety Adviser for further information.
8
In the event of a small amount of material igniting, it should be extinguished with dry sand. A container
of sand or powdered lime (calcium oxide) should be kept within the immediate vicinity when working
with pyrophoric substances.
Fire extinguishers should be readily available for immediate use in the event of a fire.
If the container of material has ignited then evacuate the laboratory immediately. Activate the nearest
fire alarm call point and inform the School fire warden of the location of the incident and substance
involved.
SAFE SYSTEMS OF WORK WITH PYROPHORIC SOLIDS
Handling Pyrophoric Solid Reagents
Pyrophoric solids are ideally used in a sealed glove box flushed with inert gas.
Many pyrophoric solids are sold as solutions, or dispersions in mineral oil or are covered with
hydrocarbon solvents to facilitate use.
Small quantities of mildly pyrophoric solids (such as lithium aluminum hydride and sodium hydride)
may be handled in the air for brief periods of time, but containers must be flushed with inert gas before
storage. The bulk material in containers must be maintained under an inert atmosphere (e.g. under a
funnel of inert gas) and flushed with inert gas before storage.
Transferring and Weighing Pyrophoric Solid Reagents
 Gather all necessary experimental equipment first to avoid prolonged exposure of pyrophoric
solids to air.
 Weighing alkali metals: Cut desired piece of alkali metal under packing oil using a knife.
 Using tweezers, transfer to adjacent flask containing toluene or heptane to rinse off oil.
 Use tweezers again to transfer to a weighed flask of toluene and measure weight to determine
mass of metal.
 Use tweezers again to transfer to desired reaction flask.
 AVOID low boiling rinses such as ether and pentane that tend to condense water upon
evaporation.
Cleaning Pyrophoric Reagents from Equipment.
 The quenching method must be set-up prior to any manipulation of the pyrophoric material so
that there is no delay to the quenching process.
 Small traces of metals are easily missed and so care must be taken to ensure that everything
that has been in contract with the pyrophoric material must be quenched: this includes weighing
paper, spatulas, tweezers, flasks. Wire presses (e.g. for preparing Na wire) should be examined
carefully as they contain thin folds that can trap traces of metal that are not readily accessed by
solvents.
Specific Recommendations for Working with Pyrophoric Solid Reagents
Lithium Aluminum Hydride reacts violently with water and has a significant heat of solvation.
Therefore DO NOT add solvent to dry LiAlH4. Instead, slowly add LiAlH4 to anhydrous solvent in the
reaction flask. The initial small amount of LiAlH4 will react with any trace amounts of water.
Potassium metal is considerably more reactive than lithium or sodium.
Potassium metal oxidizes to potassium oxide (K2O), potassium peroxide (K2O2), and potassium
superoxide (KO2). The yellow peroxides are shock-sensitive and can explode when handled or cut.
Therefore dispose of potassium metal as hazardous waste if old or if significant amounts of yellow
crust is visible.
The mineral oil of potassium hydride or sodium hydride dispersions can be rinsed off using a light
hydrocarbon solvent such as hexane. Caution: the hydrocarbon rinsings will contain small amounts of
9
the pyrophoric material and must be quenched carefully. Rinsing is easily accomplished in a glove box
or can be done in a hood UNDER CAREFULLY CONTROLLED CONDITIONS. Weigh out desired
amount of dispersion and seal in a flask under nitrogen. Add dry hexane via syringe, swirl, and let
metal hydride settle. Slowly syringe off hexane and then carefully discard into a separate flask
containing isopropanol. Repeat rinse procedure.
AVOID low boiling rinses such as ether and pentane that tend to condense water upon evaporation.
Sodium amalgam, Na(Hg), (or potassium amalgam) is prepared by dissolving sodium into liquid
mercury. This highly exothermic process produces the intermetallic compound NaHg2 with enough
heat to cause local boiling of the mercury. Thus it must be performed in a hood under dry nitrogen
gas. The grey solid produced has the reducing potential of sodium, but is more air stable.
FURTHER SOURCES OF INFORMATION
Bretherick’s Handbook of Reactive Chemical Hazards, 7th Edition, P.G.Urben, ISBN 0-12-373945-4
Hazardous Laboratory Chemicals Disposal Guide, 3rd Edition, Margaret-Ann Armour, ISBN 1-56670567-3
Technical Bulletin AL-134, Sigma Aldrich,
http://www.sigmaaldrich.com/etc/medialib/docs/Aldrich/Bulletin/al_techbull_al134.Par.0001.File.tmp/al
_techbull_al134.pdf
10