Safety with electricity

Electrical safety in the laboratories at the Department of Molecular Biology and Genetics (MBG)

Safety when working with electricity must be taken very seriously.

Discard any apparatus that fails to meet the safety standards.

Strict regulations were imposed in 1993 regarding:

  • Equipment safety
  • User familiarity with safety conditions

Everyone who uses or maintains the laboratory equipment is thus co-responsible for safety, and it is your duty to see that the safety conditions are maintained.

If in doubt, do not use the equipment and ask MBG’s staff at the workshop to deal with the problem.

New equipment and MBG’s rules and regulations

  • All new equipment must be CE marked (a mandatory requirement since 1997).
  • Unfortunately, CE marking is not a certification (as many people believe), but is simply the manufacturer’s declaration that the equipment is safe to use. You should therefore always check that the mains and high-voltage plugs are correct.
    This unfortunately shows that you need to critically assess the equipment before purchasing!

You should be aware that – in their power supply – certain American companies make use of ‘elongated, modified, composite banana plugs’ without rigid sleeves and with accompanying countersunk bushings.
These might appear to be harmless – exclusively with their equipment when it is separately connected.
However, these are extremely dangerous when used with other devices that have the correct standard safety plugs.

And who is responsible?

In 2004, MBG’s Safety Committee and heads of departments therefore drew up our rules and regulations for electrical safety in the laboratories:

  • Banana plugs, etc. with exposed electrical parts must be removed immediately
  • Sockets with spring-loaded sleeves must not be used
  • High-voltage plugs and bushings must be standardised safety plugs with rigid sleeves
  • All electrical laboratory equipment must be earthed via the mains cable, i.e. the mains plugs must be the three-pin Danish type
  • Contact MBG’s technicians before purchasing new power supplies and electrophoresis devices to ensure that the equipment complies with the department’s requirements

The most important points are described in more detail below, and reference is made to two models from 2004, showing examples of correct and wrong types of plugs.

General dangers associated with electrical equipment

  • Electric shocks cause violent muscle contraction resembling a cramp or seizure. Strong electrical currents can also result in burns.
  • The most serious electrical accidents lead to cardiac arrest, while a milder shock can cause significant discomfort.
  • You should therefore never touch any electrophoresis devices or electrical leads when they are plugged into a power source (this should actually be impossible under correct conditions).
  • Practically all fluids in the laboratory are conductors of electricity. In fact, many of them are extremely good conductors and correspond to a direct connection with the plugged in leads.
  • Electrical equipment and leads should therefore always be kept clean, dry and free of salt deposits. Never work with electrical equipment if your hands or gloves are moist (thin rubber gloves do not provide protection from high voltages).
  • Coldrooms carry an increased risk of electrical faults and accidents due to condensation problems.
  • The two most dangerous power sources are 230 volt mains and high voltages for electrophoresis devices (see below).

If you are in doubt as to whether the equipment is properly designed, keep this basic rule in mind:
All equipment must be protected against anyone accidentally touching live components in all conceivable situations!

Examples of correct plugs and the wrong ones


Correct safety plugs



Examples of wrong – and dangerous – plugs


230 volts mains electricity

All electrical equipment must be earthed via the mains cable.  This provides better protection from electric shock and accidents even when there may be some leakage in the apparatus.

Therefore, all laboratory apparatus must have a Danish 3-pin main plug that is earthed, 2 round pins and one flat “earth “pin below!

All laboratory equipment must have a three-pin Danish mains plug that is earthed, with two round pins and one flat earth pin at the bottom.

  • Mains cables with German plugs appear to be of a good quality, but they are not earthed in Danish sockets.
    You must not use them – so get rid of them and order the right ones from the electronics workshop.
  • Connectors and cables must be perfect. Users should ensure that mains cables are in good condition, i.e. there is no damage to mains and equipment plugs (intact pins, no damage to the insulation).
    Please also note that:
    Cables are of a sturdy quality with no splits or scorch marks from hot plates, etc.
    They should sit firmly in the cable relief on connectors and equipment.
    If you are in doubt about the quality, throw out the cable and get a new one!

Residual current relays are not infallible
Please note that residual current relays only ensure the transfer from 230 volt mains connections to earth. Prior to this, you can still get an electric shock and drop items such as glass and hazardous liquids.
If you touch both ‘active’ mains conductors, you can be exposed to several kilowatts – for a matter of hours.
And residual current relays provide no protection at all from faults in the power supply output voltage.

Electrophoresis devices and high-voltage connections

Voltages are often very high, and this places great demands on equipment, cables and connectors (plugs and sockets).

  • Cables should be of the best quality – and always with approved safety plugs.
  • Gel appliances and cables should be insulated against 1000 volts (possibly 1500 volts).
    Silicon rubber cables that give a continuous heat should be used
    Avoid rubber tubing (they crack) and thin plastic tubing that melts in contact with the edge of a hot plate.
  • Never use transformers, adjoining cables or adaptors that can transform the approved safety sockets to those that are less safe.  They are dangerous and must be discarded.
  • Cables and gel appliances must be insulated for at least the same voltage as the safety plugs.

Correct type of safety plugs and bushings

At MBG, we exclusively use two types of safety plugs, and other types are not permitted in the laboratories. Please note that both types have rigid insulation sleeves, so that the plug pins cannot be touched directly:

4 mm safety plugs that are standard for most equipment. These are approved internationally and are suitable for approximately 1000 volt – provided they are dry.

2 mm safety plugs, with a longer, stronger sleeve, that are suitable for up to approximately 1500 volts.

Please note: Connectors with spring-loaded sleeves are unsuitable as they are only for low current (to minimise an unforeseen short circuit). The same applies to the old-fashioned ‘banana plugs’ (and corresponding sleeves and extension cords). They must be discarded because they are much too dangerous and do not comply with safety regulations.


Power supply safety

  • Power supplies must naturally have the right output sockets corresponding to the correct safety plugs
  • 4 mm safety sockets have mouldings suitable for the plug’s covering.
  • 2 mm safety sockets are deeper, corresponding to the long plug’s bigger covering.
  • Equipment with old-fashioned sockets for banana plugs must be discarded.
  • Power supplies with high voltage current must be insulated with respect to “earth” or have a safety circuit that breaks when earthed (this can be checked by MBG's staff at the workshop).
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