Although Electron Microscopes are high tension, water-cooled pieces of equipment, potentially capable of emitting penetrating and dangerous X-rays, they have been installed in strict conformity with all regulations for such equipment. The emission of radiation from the column is prevented not only by lead screens specially fitted for the purpose but also by apertures and other removable components normally present in the column during standard modes of use. Thus most electron microscopes are extremely well shielded and do not produce exposure rates greater than background.

When operating an electron microscope, note:

  • Users must adhere to the techniques in which they have been trained.
  • The instrument must not be operated when partially dismantled or before all covers and components normally present have been correctly replaced (for instance when servicing or maintenance has just been carried out).
  • No structural alterations or modifications to the instrument may be made without expert advice and subsequent checks must be made to confirm that hazards have not been introduced by such modifications.
  • All accidents, malfunctions, or suspected faults must be reported to a responsible person. Only trained technical staff may attempt to trace, or rectify, electrical or mechanical faults.

The TEMs use SF6 gas for insulation of the high tension (HT) tank and gun chamber. If there is a significant leak of this gas as displayed on the relative gauges, the oxygen monitor in the room will set off the alarm. The EM officer in charge will put the TEM into a standby state and evacuate the room. SF6 gas gas is heavier than air and will therefore displace oxygen from floor level up. A liquid N2 spill could also activate the alarm.

If the alarm goes off: Switch off the microscope, leave the room and shut the door, access to the room must be prohibited until the gas has been cleared by the air circulation system (½-1 hr) and Sean or Mohamed alerted

All users must be shown the alarm system. The EM rooms must be labelled "authorized personnel only", and the O2 monitors should have a notice with this procedure.

General Laboratory Safety

  • The EM Users form must be completed before any work can be done in the EM laboratories. Here is a link to the registration form.
  • Handle all dangerous chemicals in the fume cupboards, wearing gloves, these are provided by the Unit. Be careful with the stains used for Negative Stain microscopy.

Osmium Tetroxide

  • Handle ampoules with disposable gloves.
  • Use double bottles and seal with parafilm.
  • Open only in a fume hood, and in a well-ventilated room.
  • Do not hold your breath when using OsO4. Your nose is a very sensitive detector of dangerous fumes.

Aldehydes and Buffers

  • Handle in fume hood.
  • Some buffers (e.g. Cacodylate and Veronal) contain toxic components, and must be handled with caution. Use gloves at all times.

Embedding Resins

  • Most embedding resins may cause dermatitis.
  • When preparing the mixtures and during embedding procedures, ALWAYS use disposable gloves.
  • Cover working areas with paper towel and wipe spills immediately with alcohol.
  • Do not use alcohol to remove resins from your skin, it increases penetration. Use soap & water.
  • Get medical attention for any suspicious skin rash.
  • Harden all waste resin before disposal, wrap discarded containers, beakers, vials, pipettes, etc. carefully.
  • Never pour any plastic containing solutions (e.g., propylene oxide-epon mixture) down the drain. They will harden.
  • All chemical waste should be placed in the waste bottles in the fume cupboard. These bottles are clearly labelled so please dispose of your hazardous waste properly. Glass and sharp objects can be placed in the specially marked plastic bins in the lab.
  • If in doubt please ask a member of staff for advice

Liquid nitrogen and cryogenic liquid handling

  • When handling liquid N2, remember to keep the doors open to avoid oxygen depletion. Oxygen depletion is the main danger from the use of liquid nitrogen - make sure you are in a well ventilated room.
  • Leather gloves and eye protection must be worn whenever handling cryogenic liquids


  • The preparation of liquid ethane for cryo work must only be done behind the shield in the fume hood. Use low flow rates of ethane to prevent splashing.
  • Gloves must be worn.
  • Ethane is flammable and potentially explosive. Do not use in the presence of flames and use only in a vented area. Once the ethane cylinder is open do not switch anything on or off in the fume hood, including the light. Do not create any static.

Critical Point dryer

  • Critical Point Dryers are potentially lethal. Do not observe them in use unless you understand the danger. The critical point dryer in the E.M.Unit is operated only by a trained technician. Do not attempt to operate it yourself.

Coaters and glow discharge unit

  • This equipment in the E.M.Unit is only operated by trained technicians. Please ask for help to get your samples coated or your grids glow-discharged. Never observe metal evaporation without goggles the intense brightness can burn your retina.

General duties

  • Users should help the EM technicians with replacement of gas cylinders when necessary.
  • Spares for EM equipment are stocked by the EM technicians, but users are responsible for ordering their own experimental supplies.
  • Office supplies should not be taken from the EM unit.
  • Please leave the equipment clean and ready for the next user. It is not the job of the EM technicians to clean up after users - they have much more important things to do.
  • Cryo tools etc must be left in the correct places, otherwise the next user's session can be messed up.
  • If items need replacing, please let the EM technicians know.
  • Please use the microscope log books to report faults or changes needed.