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Section 8: General Laboratory Precautions

8.1 Personal Protective Equipment

The Personal Protective Equipment (PPE) at Work Regulations 1992 require that where PPE is supplied it must have been assessed to ensure it is suitable for the intended purpose.

The appropriate local regulations should be consulted. In many laboratories the wearing of approved types of laboratory coats and safety spectacles is compulsory. The occupants of the laboratory should ensure that any visitors or tradesmen are similarly attired. In some laboratories additional items of personal protective equipment (e.g. face-shields, dust masks, gloves, plastic aprons, etc.) are also provided; the protection worn must be appropriate to the work being undertaken.

8.2 Protective Clothing and Footwear

Bare skin presents areas for contamination by chemicals, micro-organisms and radioactive substances etc.

The laboratory coat provides protection for the arms and body. The choice of style and fabric of lab coats provided must be arrived at as a result of risk assessment of the nature and quantities of the hazards involved and the circumstances of use. The Safety Office has issued guidance to assist in making the correct choice which can be found on the Safety Office website PDF format.

Laboratory coats may become contaminated with toxic materials and should normally be left behind when leaving the work area. They must not be worn in any area set aside for tea and coffee making or for the consumption of food or beverages.

They should be washed regularly and whenever they become contaminated with chemicals.

It is necessary to protect the feet and legs from chemical spillage or from damage from heavy equipment being dropped. Suitable footwear must be worn. The wearing of open-toed shoes or sandals in laboratories is not permitted, as their use makes the feet extremely vulnerable to injury from broken glass, spilt corrosive substances, liquid nitrogen, etc. Loose fitting sandals, especially those with no heel restraint, are not secure and may present a tripping hazard.

Loose long hair can be a danger to personal safety in the laboratory. It is readily ignited (lacquer increases this risk) or it could become trapped in equipment or machinery. Long hair should always be tied back.

8.3 Protective Gloves

Gloves may be required to protect the hands against one or more of a range of different hazards, including chemical, biological, heat, and cold. In general. no one type of glove protects well against more than one type of hazard. This makes it very important to select the correct type of glove for the intended use.

Chemical protective gloves are available in a range of materials including natural rubber, neoprene, nitrile, butyl, PVA, PVC and viton. The degree of protection against chemical permeation depends on the glove material, its thickness and the way it is made. Different materials offer widely ranging resistance to permeation as defined by the “breakthrough time”. Glove suppliers provide information to assist in glove selection. It should be remembered that the liquid may be the solvent for other more hazardous chemicals being used and as such will enable these to diffuse through the glove with the solvent, which may also carry the chemical to into the skin.

Solvents may also adversely affect the physical characteristics of the glove and impair its protective properties, for example by leaching plasticising agents out of the glove causing it to become more brittle, cracking and thus leak.

It is important to check gloves for damage such as holes, cuts and distortion. Reusable ones should be examined for signs of internal contamination.

Gloves which bear the term ‘Examination Gloves’ on the box are intended for use in clinical examinations where the patients are to be protected from contamination by the person examining them. These are termed Category 1 gloves and are suitable only for low risk activities. In a laboratory setting, their value is very limited, because they offer little or no protection to the wearer against either biological or chemical hazards. They are of use only in preventing the work from being contaminated by the wearer. 

Category 3 gloves will bear CE mark plus four digits e.g. CE 0121 and will be suitable for protection against biological and chemical hazards for most of the uses in the laboratory.

The University Safety Office has published more detailed guidance PDF formaton the selection and use of gloves for protection against hazardous substances. 

Gloves worn in the laboratory must be removed and placed for disposal before leaving the laboratory suite in which such work is being undertaken. The wearing of potentially contaminated gloves in the corridor, rendering others at risk, is strictly forbidden, unless, as a result of risk assessment, the School has sanctioned alternative procedures (e.g. having a glove free hand to negotiate doors).

The normal requirements on removal of protective clothing prior to entering offices, seminar rooms, rest areas and when entering public areas apply.

8.4 Allergy to Natural Rubber Latex

Latex gloves are widely used to protect against exposure to harmful substances and also to protect work from contamination. Latex allergy is particularly associated with the use of powdered latex gloves – the powder helping to disperse the latex protein, resulting in exposures fifty times higher than arises from non-powdered gloves. The powder used in these gloves can also penetrate the pores of the skin and when combined with sweat produced within the glove this can lead to adverse skin reactions.

The use of pre-powdered latex gloves is prohibited within the University, because of the risk of these provoking dangerous allergic reactions and skin conditions.

The use of disposable non powdered latex gloves must be avoided wherever possible and in all cases where there exists a viable and practicable alternative to the use of latex gloves the alternative should be utilised. Their use is only permitted where latex provides a distinct advantage over alternative gloving materials for the task and the justification for selecting latex must be documented in a risk assessment.

Where latex gloves are used, this must be fully justified, documented and supported by a risk assessment. Users must be provided with information on the risk of latex allergy, information on how to recognise possible allergic reactions to latex and on the need to report suspicion of allergic reactions to the Occupational Health Department.

Suitable alternative gloves must be provided for users with diagnosed latex allergy. Advice on any additional necessary precautions should be sought from the Occupational Health Department as in more serious cases latex may need to be removed from the entire area.

Further and more detailed information is available on the Safety Office website PDF format.

8.5 Hygiene

During laboratory work contamination on the hands may not be noticed immediately. Never touch any part of the body (the area around the eyes is especially vulnerable) without washing your hands first. Always wash off any chemical contamination immediately. This includes washing contaminated gloves. If you do contaminate anything (e.g. the bench top or water tap) clean up the contamination immediately. Always wash your hands before leaving the laboratory.

8.6 Food and Drink

Food and drink for human consumption must not be stored, prepared, or consumed in laboratories. Special areas are set aside for the consumption of food or beverages. Where food or drink is required for human consumption under laboratory conditions, i.e. as an authorised research or teaching programme, then special arrangements to ensure the safety of these are required.

Food and drink along with preparation equipment and eating utensils must be stored and handled separately from chemicals and biologically toxic materials. Separate refrigerators must be provided for the storage of food and drink and laboratory refrigerators should not be used.

8.7 Smoking

Smoking is prohibited in all laboratory areas.

8.8 Experimental Work

Ensure that you are properly briefed, or that you have done your literature work before attempting a new experiment. If you do not fully understand an instruction, are unsure how to operate a piece of equipment, or are unsure about the potential risks of an experiment, then seek help from a competent person before proceeding further. Unauthorised experiments are strictly forbidden.

It is important that communal work areas and facilities are kept scrupulously clean and tidy. The next person could be injured by the debris or chemicals you have left behind.

Take care when entering or leaving a laboratory to avoid bumping into someone carrying chemicals or equipment. Never run! Chemicals must be transported in purpose-made carriers; a suitable trolley should be used for transporting other bulky or heavy items.

8.9 Emergencies

Before starting an experiment you must consider what emergency action to take should it go wrong, or if the apparatus should break.

When the fire alarm sounds: If practicable make the experiment safe (e.g. turn off heating sources), extinguish naked flames, close windows and doors and follow the local evacuation procedure.

When starting work in a new area, you should check the location of all fire exit routes, the location of the fire fighting equipment and internal and external telephones.

8.10 Out of Hours Working

Laboratory working by individuals or the unattended operation of experimental apparatus outside of normal hours must be subject to appropriate local regulations and risk assessment. A contact telephone number must be left in case of emergency.

Leaving experiments unattended should only be done where the risk assessment has identified that this it acceptable and emergency contact and action details must be left on the entrance to the laboratory.

8.11 Glassware

Glassware must always be handled carefully. Glass tubing can easily be broken and can cause severe damage to hands. Protect you hands and use appropriate lubricant when fitting flexible plastic or rubber tubing over glass tubing, or fitting a glass pipette into a safety filler or dispenser. Particular care should be taken when breaking ampoules open. Where the contents are hazardous, e.g. toxic, carcinogenic, infectious, a proprietary ampoule breaker should be used.

Any crack considerably reduces the strength of glassware, and the item should either be sent for repair before further use, or discarded. Chipped glassware should also be discarded. The appropriate waste disposal methods must be used.

8.12 Syringes

Contaminated or broken syringes and syringe needles must be placed in one of the “Sharp-Safe” containers provided (i.e. a sharps container that complies with BS 7320:1990 and/or type approved under the Carriage of Dangerous Goods (Classification, Packaging and Labelling) Regulations). When full these containers are sent away for incineration. They should not be placed inside other bags. Do not place syringes or other sharps in the general-purpose waste bins. Further information on use is contained in Section 10.5.

8.13 Vacuum Systems and Manometers

Glass systems are particularly vulnerable and should be protected against the risk of implosion should mechanical defects develop while the system is under vacuum. Do not evacuate thin-walled or non-spherical glass flasks.

When liquefied gases are being handled there is a risk of over-pressurising the system, leading to an explosion risk, if valves are not opened and closed at the correct times or in the correct sequence.

Liquid nitrogen when exposed to the air slowly condenses oxygen, and may assume a pale blue colour. Liquid oxygen presents a severe fire risk and it reacts violently with a range of materials and chemicals.

Manometers should be protected against damage. Mercury manometers must be provided with a tray to contain all the mercury in the case of any spillage or breakage. Any spillage of mercury must be cleared up immediately and disposed of as hazardous waste.

8.14 Electrical Equipment

Electrical equipment is checked regularly and should normally carry an in-date sticker to show this. Out of date equipment should not be used. The guidance contained in the University Code of Practice for Electrical Safety PDF formatshould be followed.

However, faults can occur between checks. Therefore always check before use for damage, loose wires or exposed terminals and for water or solvent spillage.

Faults must be reported immediately to a competent person and a suitable notice must be attached to the equipment prohibiting further use until repairs are made.

8.15 Photographic Dark Rooms

Because it is often necessary to work with reduced lighting levels it is most important to ensure good housekeeping. Keep floor areas clear and avoid trailing cables. Chemical, electrical and mechanical safety must be carefully considered and it is important to ensure good ventilation.

8.16 Cryogenic Gases

Cryogenic gases in the form of liquid nitrogen and helium are often associated with work in laboratories within the University.

The properties of these gases are as follows:

Property

Nitrogen

Helium

Boiling Point1 -196oC -269o
Liquid/Gas Ratio2 683 739
Volume of liquid per m3 that will reduce the oxygen level to 19%. 0.14 litre 0.13 litre

1Temperature at which gas turns to liquid.

2This is the expansion factor. 1 litre of liquid nitrogen will expand to produce 683 litres of gas.

Hazards associated with the use of these gases are:

1. Asphyxiation due to oxygen deficiency:

Normal atmosphere contains 20.9% oxygen by volume. Increasing the amount of cryogenic gas into the environment will displace the oxygen. The physical effects are increasing pulse rate tiredness, headaches and dizziness, fainting. The severity and speed of onset of these effects increase as the oxygen level decreases and beneath 10-12% they can occur without the person’s knowledge, without prior warning and can prove fatal. The liquid gas ratio indicates the volume that 1 litre of liquid gas will expand to fill when spilt. This happens instantaneously and thus a spill of liquid gas in a poorly ventilated room can have very serious consequences.

Precautions: Confined spaces present a problem. Store and dispense gas only in well ventilated areas. A risk assessment should have been carried out to establish if the oxygen concentration could drop below 19% in the event of spillage. If this is the case consideration must be given to provision of an oxygen monitoring system for the work area.

Lifts are confined spaces and cryogenic gases must not be transported in them unless a risk assessment has established that oxygen deficiency will not occur under the conditions and quantities to be used. If oxygen deficiency could occur then the vessel should be unaccompanied. The use of additional personnel and barriers will be required to prevent entry into the lift. These measures should be described in a standard operating procedure. Further advice can be obtained from the Safety Office, which can carry our oxygen monitoring.

2. Cold burns:

Prolonged exposure may lead to frostbite and the destruction of body tissue. This may not be immediate or obvious. Also the skin may freeze instantly to cold surfaces and attempts to remove the skin can cause serious damage.

Precautions: The following personal protective equipment should be worn.

      • Lab coat with apron over top will prevent liquid gas entering pockets and areas where spillage can collect.
      • Thermal gloves of non-absorbent waterproof material. They should be securely banded at the wrist or arm.
      • Full-face visors must be worn to prevent liquid splashes to eyes, face and mouth.
      • Full shoes that extend up the ankle allowing trousers to fit over the shoe.
      • Tongs and forceps for handling vials.
      • First aid response is given in Section 4.4 of this manual.

3. Cold effect on lungs:

Inhalation of cold mists, gases or vapours can be serious and lung damage may result. This will be a consideration for larger scale use. Ensure area is well ventilated and wear a face visor.

4. Ice plug formation:

These may form in the neck of Dewars when moisture comes into contact with the cold gas in the neck of the Dewars. This can then form a seal across the neck preventing normal venting and leading to increased gas pressure. The ice plug may be ejected at high velocity or the Dewar may explode.

Precautions:

      • Always fit the Dewar’s protective cap
      • Ensure the cap is in good condition
      • Do not leave uncapped Dewars outdoors in moist environments
      • Ensure Dewars are fully emptied after use

In the event of an ice plug being found in the neck of the Dewar immediately evacuate the area.

5. Explosion due to rapid expansion:

Due to the high liquid:gas expansion ratio if liquid cryogen becomes trapped in a confined area or container can cause the container to explode due to rapid expansion. Examples of where this can occur:

      • Removing cryogenic vials from liquid nitrogen – liquid within the vial can cause the vial to explode as the vial warms up. Always place vials behind a screen or within a robust container and wear a visor, or ensure vials are stored only in the vapour phase of the freezer.
      • Cryogenic liquid becoming trapped between the inner and outer walls of certain types of dewars which have seals around the rim of the dewar.  Avoiding use of this type of dewar is strongly advised, where they are in use it is important to inspect dewars regularly for any cracks/breaks in the seal and withdraw from use.

6. Oxygen enrichment:

This may occur around the hose of a pressurised Dewar, or in the bottom of an open Dewar. Since liquid nitrogen and liquid helium are colder than the boiling point of liquid oxygen, air coming into contact with a very cold surface will cause oxygen to condense out of the air. Liquid oxygen may drip from the hose giving the impression of a leak. These effects can result in oxygen-enriched air being formed, which present an additional fire hazard. Also cryogenic liquid oxygen dripping onto surfaces might cause embrittlement.

Precautions: No smoking or naked flames in the vicinity of cryogenic transfer.

Solid Carbon Dioxide Ice [Cardice]:

Cardice will produce carbon dioxide gas, which is an asphyxiant. It is also is extremely cold and can cause cold contact burns. The precautions outlined for the hazards associated with cryogenic gases should be adopted for handling cardice.

Treatment for cryogenic burns - see Section 4.4

Use of Small Dewars – potential explosion hazard

It should be noted that the small DILVAC type of dewars can lead to potential problems because of the seal becoming defective and allowing liquid cryogen between the inner and outer layers of the dewar - the rapid expansion as the liquid becomes gaseous can then lead to an explosion. Ideally such dewars should be replaced with ones that do not have a seal around the top. Certain suppliers have dewars that are not constructed in this way because of this potential risk.

Where the DILVAC style of dewar is still in use, managers must ensure that the seals are inspected for defects and that any that are defective are immediately taken out of use. The best course of action would be to replace any that have seal defects with a different type of dewar, however it is possible for suppliers to provide replacement seals and instructions on how to fit them.

If this type of dewar remains in use managers must ensure that users are made aware of this potential problem and of the importance of inspecting the seal carefully before each use to ensure it is intact.

8.17 Use of Personal Communication and Entertainment Devices in Laboratories

Due to the more hazardous nature of work undertaken in labs and workshops the University has issued guidance to restrict the use of mobile phones, personal stereos, mp3 players and i-pods, etc. in these areas. More detailed information is available on the Safety Office website PDF format.

8.18 Transport of Hazardous Substances

The transport of hazardous substances by road, rail and air is subject to very specific and complex regulations. The University has therefore engaged the services of a Dangerous Goods Safety Adviser to provide advice on the correct means of transporting hazardous substances and biological materials. For further details of this service contact the Safety Office.

 

Safety Office

Pharmacy Building - Lower Ground Floor
University Park
University of Nottingham
Nottingham, NG7 2RD

Telephone: +44 (0)115 951 3401
email: bb-safety-office@exmail.nottingham.ac.uk