Health and Safety in
the EM laboratories
The following safety considerations
are specific to the EM laboratories
Please note that the EM laboratories are
for authorized personnel only and must be labeled as such. For general
departmental safety information, please click here.
A copy of the following safety information can be found on the notice board
in the laboratory.
The EM laboratory is a category 2 containment lab and all category 2 procedures
must be followed:
The laboratory COSHH form must be read and
signed before any work can be done in the EM laboratories. This form is
kept in the departmental office.
Be careful with the stains used for Negative
Stain microscopy. Uranyl Acetate is weakly radioactive, phosphotungstatic
acid and ammonium molybdate are toxic, and sodium silicotungstate is harmful.
Handle the heavy metal salts with gloves. Handle the powder gently to avoid
creating dust and clean up the balance and bench areas immediately after
Infectious samples such as prions and toxins
are used within the laboratory. All such samples have associated COSHH
procedures. If you are not sure what a sample is, treat it with caution.
All samples which carry a hazard risk should be labeled as such.
All waste solvent should be placed in the
waste solvent bottle in the safety cabinet. Chemicals for removal should
be referred to the Departmental Safety Officer.
Sharps are collected in marked sharps bins
and are then taken to a collecting point.
The gas supply to the wet lab has been disconnected.
Do not use naked flames in the lab as they are a severe risk, use a hotplate
The floors in the laboratory have been sealed
to protect them from liquid nitrogen. Chairs with wheels must not be used
on this surface as they are a potential slip hazard.
The weekly laboratory rota maintains the liquid
nitrogen tanks and checks cleanliness and safety. The tidier the laboratory
is, the safer it is.
Oxygen depletion is the main danger from the
use of liquid nitrogen. Oxygen monitors have been installed in the laboratories
and will issue an alarm if the oxygen levels in the room fall to dangerous
levels. All new users must be shown the alarm system. Sometimes the refilling
of dewars can cause the alarm to beep. If the alarm beeps, check the reading
on the oxygen meter. If the reading is less than 19%
leave the room. The alarm can be stopped with the red
mute button but if the meter reads less that 19%
or the alarm restarts, it is not safe to stay in the room and it must
be evacuated. Once the room has been evacuated and the nitrogen has been
allowed to disperse, the oxygen meter can be checked but by no less than
two people. One person should hold their breath and check the meter reading
while the other holds the door and watches the person checking the meter.
The room can be used again once the reading has risen above 19%. The only
button to be touched on the oxygen meter is the mute button; at no point
should the settings on the meter be altered by anyone other than a service
engineer or EM lab manager.
Eye protection and gloves must be worn whenever
handling cryogenic liquids.
When handling liquid nitrogen remember to
open any curtains and doors to avoid oxygen depletion.
For more information the College's regulations
on liquid nitrogen safety, click here.
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 and eye protection 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.
You must wear the correct safety glasses when operating the laser.
Make other people in the vicinity aware that
you are using the laser.
Do not look at the laser beam directly.
Remove the key from the laser when leaving
the room at any time. Do not leave the laser on and unattended.
microscope emergency shut down
In the case of an emergency, such as a
fire or a building evacuation, follow the instructions below. However,
personal safety remains a priority at all times and by no means should
you put yourself at risk.
Press the OFF button on the Emergency Control
Panel, which is on the right hand side of the EM column. The microscope
will shut down and minimize any hazards to itself or anyone nearby.
Switch off the PC by pressing the on/off button
on the main PC box. Do not use the standard Windows shutdown procedure.
Immediately leave the microscope room and
follow the normal College evacuation procedures.
If there is a risk of electrocution, the main
power switches (grey boxes with levers) for each microscope are located
near the exit doors of the microscope rooms.
The FEG microscope uses sulphur hexafluoride
gas (SF6) for insulation of the high tension (HT) tanks and
the emission chamber of the F20. The gauge on the HT tank should read 4.5
bar. If the pressure drops below 4 bar, there may be a leak. While
this gas is non-toxic it is heavier than air, and will displace oxygen
from the floor level upwards. If there is a significant leak of this gas
the oxygen monitor in the room will beep. The microscope will automatically
switch off and the room should be evacuated according to the following
If the microscope has not shutdown automatically,
press the OFF button on the Emergency Control Panel on the right hand side
of the EM column. Leave the room. Shut the door and put up a notice prohibiting
others from entering.
If a leak occurs during the daytime contact
the EM Laboratory Manager, Dr Luchun Wang. If the leak occurs out of hours contact
the Lab Manager as soon as possible so they can contact Phillips to notify
them of the SF6 leak.
The College attendant on duty at the front
desk should be notified of the reason for the alarm (x6031).
Access to the room must be prohibited until the gas has been cleared by
the air circulation system (½ - 1 hr) and the oxygen levels have
recovered to normal. To check that the gas has dispersed, follow the safety
instructions on oxygen depletion found in the liquid
For routine venting of the SF6 by
the service engineer, the gas should be vented into one of the balloons
stored for this purpose. The balloon can then be emptied outdoors in an
This page was last updated in October 2012