How to Keep Yourself Safe
Safe working is best achieved by thinking about what you are doing and by paying attention to the task in hand.
✤Concentrate on the task in hand; accidents occur when you are not concentrating.
✤Take the time to carry out the procedure properly, rushing or taking short cuts can lead to dangerous errors.
✤Stay alert and check for potential hazards, e.g. faulty equipment, poor or missing labels on reagent bottles.
✤Be safety conscious, carelessness or neglecting safety precautions endangers you as well as your colleagues.
✤Be careful when opening doors and entering laboratories, particularly if you cannot see what is behind them.
✤Be overconfident and assume 'it can't happen to me', taking safety for granted can set the stage for an accident.
✤Fool around or indulge in horseplay in a laboratory; this is a recipe for disaster.
✤Eat or drink or smoke in a laboratory, all areas of the University are no smoking areas.
Examples of Hazards and Safe Practice
You will inevitably use a number of reagents; whilst we cannot give an exhaustive list here, there are a few simple rules which will minimise potential hazards. ✤Always read the label. All reagents will be labelled and any which are potentially dangerous will be identified as such . Never use unlabelled reagents
✤Always read the COSHH Hazard Assessment Form Make sure you know the properties of the reagents which you are to use and are potential hazards: is it toxic?, Is it inflammable?
✤Never attempt to identify a reagent by smell
✤Report any spillages to the member of staff in charge
As a general rule spillages of concentrated acids are neutralised by solid sodium carbonate and then washed away and spillages of concentrated alkalis are neutralised by solid ammonium chloride before washing away.
Extra protective clothing, for example, an apron worn over the lab coat and gloves and goggles should be worn during decontamination.
✤Dispose of reagents as directed and ensure the waste is placed in the correct container. Organic solvents which may be immiscible with water or flammable should never be discarded into the drain.
✤Never look into tubes or flasks during heating and make sure they are not pointing towards any persons near you.
✤Use a fume cupboard when instructed in order to prevent hazardous fumes or gases from entering the laboratory
✤Never pipette by mouth, always use a pipette filler. In most cases the 'PiPump' is the filler provided and is satisfacory as long as the following procedure is employed
✤Always make sure the pipette is clean and dry
✤Do not use excessive force when inserting the pipette into the filler
✤Always hold the pipette close to the 'filler' end and insert into the filler with a twisting motion
✤Never hold the pipette in the region where it is graduated
N.B. until you know what it is and what it does, don't use it and treat any chemical as hazardous.
This is not an exhaustive list but an indication of what you may be dealing with.
|Aniline||Fat soluble, adsorbed through the skin||Toxic|
|Benzene||Chronic poison: small quantities over a long period can cause leukaemia. Replace with toluene where possible||Toxic, Flammable|
|Bromine||Both liquid and vapour phase will attack eyes and mucous membranes.||Corrosive|
|Cadmium||Probably the most lethal metal: all salts are highly toxic by ingestion||Toxic|
|Carbon disulphide||Absorbed through the skin||Toxic, Flammable|
|Carbon tetrachloride||Absorbed through the skin||Toxic|
|Chloroform||Absorbed through the skin||Toxic|
|Trichlorethylene||Absorbed through the skin||Toxic|
|Lead||All soluble salts toxic in large amounts. Cumulative poison by inhalation which can lead to brain damage. Adsorbed by plants||Toxic|
|Mercury||Vapour from the metal is a toxic cumulative poison||Toxic|
|Sodium hydroxide||Supplied in solid form as pellets. Very corrosive. Avoid skin contact and wash spills from skin immediately with large quantities of water. Generates heat on solution||Corrosive|
|Sulphuric acid||Very corrosive. Most accidents occur on dilution - always add acid to water very slowly and cool and stir constantly. This rule applies to all concentrated acids. Avoid skin contact||Corrosive|
|Most compounds of these heavy metals are toxic||Toxic|
|Cyanides||Avoid contact with skin, inhalation and ingestion. Cyanide residues must be placed in the 'Cyanide Residue Bottle': never pour cyanide residues down the sink. A cyanide antidote is available in every teaching laboratory - make sure you know where it is and how to use it. The life it saves could be yours.||Toxic|
|Pesticides ; fungicides and herbicides||Avoid contact with skin, inhalation and ingestion||Toxic|
✤ensure the equipment is switched off before connecting it to the mains.
✤check the lead and plug top are not cracked or damaged before 'plugging' into the socket.
✤route the mains lead so it does not constitute a hazard or can become wet or damaged.
✤use the equipment in accordance with its instructions and only for the purpose for which it was designed.
✤report any damage or malfunctions immediately and make no attempt to repair the equipment yourself.
Bunsen burners burn therefore:
✤ensure long hair, loose clothing, laboratory notebooks etc., do not come into contact with the flame.
✤in bright sunlight a hot Bunsen flame will become invisible so whenever possible close the air control collar so the flame becomes luminous and therefore visible.
✤do not use a Bunsen immediately below a cupboard or any other equipment not designed to use direct heat.
✤always turn off the Bunsen when you leave the laboratory.
A negative pressure ( vacuum) is often used in the laboratory to aid filtration or in freeze drying, or in evaporation at low temperature etc.
Most lab systems are constructed of glass although some plastic or metal systems are available; when using glass or plastic equipment under negative pressure, check that:
✤appropriate 'thick walled' equipment is in use since 'ordinary' glassware will not will withstand the external pressure.
✤there are no deep scratches or cracks present.
✤the equipment is not subject to thermal shock i.e. sudden heating or cooling.
✤'ball and socket' joints and not 'cone' joints are used wherever possible
✤stop cocks are lubricated and are operated smoothly and slowly.
✤the equipment is shielded by a purpose built safety cage or is wrapped in a cloth or rubber film
✤rubber bungs are large enough not to be 'sucked' into the flask.
There are relatively few sources of physical injury in the laboratory, however this is the main source of hazards in the workshops so following general rules apply:
✤ensure there is no obvious damage to any equipment.
✤check all guards and electrical or mechanical interlocks are working and are in use.
✤make sure loose clothing, e.g. unfastened lab coats, ties etc. cannot become entangled in equipment and that long hair is tied back.
✤always use the equipment as directed.
The following are examples of specific mechanical hazards
should never be operated with the lid open and most have locks which prevent the lid being opened when the rotor is moving.
✤the load should be balanced diagonally across the rotor.
✤never try to stop the rotor by hand even if it is travelling slowly; allow the rotor to 'run down' to a standstill.
Mixers and Blenders
✤always use eye protection
✤never put stirrers, spatulas etc. in the chamber whilst the blades are turning
Non ionising radiation
There are essentially three categories of what is frequently referred to as 'light'; ultra-violet 00-400 nm, visible ca 400-800 nm and infra-red 800-1200 nm.
Ultra-violet radiation is potentially the most harmful; the eyes are particularly vulnerable and eye protection must be worn.
Some 12 or so hours after unprotected exposure a severe pain develops which can persist for a week, severe exposure can result in permanent damage whilst chronic exposure is mutagenic and can result in skin cancers.
Ultra-violet sources are used in:
✤chromatogram scanners and other scanners used to detect fluorescent compounds.
✤microscopes with a UV light source.
Ultra-violet is also produced by:
✤electric arcs including 'electric welders'.
Lasers produce a highly concentrated pulse of light which is dangerous to the eyes. The cells of the cornea can be destroyed with attendant excruciating pain whilst pulses passing through the lens can be amplified some 106 times which will produce a blind spot on the retina.
There is a more detailed section on the use of glassware on this site however the following safety implications should be noted:
✤Glassware is used in large quantities in virtually all practical exercises and there is a considerable variation in quality, physical strength and resistance to heat.
✤'Pyrex' heat resistant glassware must be used when heating liquids and only 'thick walled' glassware must be used with vacuum systems.
✤Volumetric glassware - measuring flasks, cylinders, pipettes etc. or reagent bottles must never be heated.
✤The larger reagent bottles such as Winchesters (2 litre,5 litre) must never be carried 'loose' particularly by their necks; special carriers are available and must be used.
✤Never use glassware which is cracked, badly scratched or chipped.
Cryogenics: Liquids and Solids
By definition cryogenics implies extreme cold and this is perhaps the principal hazard. Skin and tissue damage similar to 'burns' or 'scalds' can result and skin will freeze and stick to 'solid carbon dioxide'.
✤Wear protective clothing, thermally insulating gloves and goggles or face mask.
✤Store in well ventilated areas and in ventilated 'Thermos' vessels.
✤Liquid oxygen also increases combustibility therefore contact with oils greases and other flammable materials must be avoided.
Gases and Gas Cylinders
On occasions you may be required to use equipment which requires a compressed gas source, usually from a cylinder or 'gas bottle' and there are two principle hazards associated with these:
✤physical injury caused by the weight and construction of the cylinder itself.
✤injury caused by the flammable or toxic nature of the contents.
It is best to treat any compressed gas,regardless of its nature, as a potential hazard , however some of the common gases may have have particular potential hazards associated with them.
|Compressed air||Misuse can result in serious injury; air can be forced into the bloodstream particularly if scratches or wounds are present. Similarly do not use compressed air to dry solvents from the skin as these can also be forced into the bloodstream.|
|Hydrogen||Forms an explosive mixture with air at between 4-75% hence ventilation is essential and naked flames must be avoided. Rapid opening of the cylinder valve can cause ignition through sparks from static electricity. Hydrogen is lighter than air thus any leaks rise towards the ceiling and any lighting or other equipment. If you suspect a hydrogen leak do not use the room lighting.|
|Hydrogen sulphide||Extremely toxic - maximum permitted exposure 20 ppm:
✤Perceptible odour ( classic rotten eggs smell) - 0.77 ppm
✤Paralysis of the olfactory centre - 100 ppm
✤Loss of consciousness - 700/900 ppm
✤Paralysis of respiratory centre and death - 5000 ppm
|Oxygen||More than half the accidents with compressed gases are associated with compressed oxygen. Increases in oxygen increase combustibility, for example a rise in oxygen level from 21% to 24% causes clothing to burst into flame rather than smoulder.|
'Liquified petroleum gases or LPG'
|All are inflammable and a level of 2% - 10% in air produces an explosive mixture. Generally heavier than air so an 'LPG' leak will 'flow' down stairs or collect in sumps etc. which can produce a suffocating as well as an explosive atmosphere.|
|Carbon dioxide||Valves can become extremely cold as the gas vapourises and the dangers associated with extremely cold surfaces apply.|
On completing a practical or other laboratory session
Before you leave the laboratory make sure you have:
✤extinguished all naked flames from Bunsen burners etc.
✤allowed all hot equipment, e.g. tripods, gauze, hot plates etc.to cool before returning them to storage cupboards.
✤dispose of waste solvents to the appropriate bottles.
✤dispose of toxic or corrosive reagents into the appropriate bottles and rinsed any containers with water as directed.
✤switched off or isolated all electrical equipment.
✤cleared your bench and wiped the surface down.
✤taken off your lab coat.
✤washed your hands.
✤Make sure you have your Lab notebook and that it has not become contaminated during the session