Operating Manual Leica EM ACE600
Version 01/19
Page 12
Estimation of lethal GN
2
– concentration in closed rooms.
Full-load values (10 kV, 3.5 mA, -150 °C), room temperature ~25 °C
Size of the room [m
3
]
10 21 31 42 52 62 73 83 94 104
Time to achieve critical
concentration [h]
1 2 3 4 5 6 7 8 9 10
Fig.1.1: When working with LN
2
for refilling the Dewar avoid protective
glasses (a), boots (c), walking shoes (e) and protective gloves (g) out of
which the LN
2
cannot easily escape if entered. LN
2
splashing into the closed
protective glasses (a), open boots (c), shoes (e) or protective gloves (g)
evaporates suddenly and can cause serious burns.
Always use protective glasses (b) with side protection which are open at the
top and at the bottom. Only use boots if you have loose (not narrow)
trousers coming outside the boots (d) and completely covering the gap.
Wear only open slip-on sandals (f) in the lab, no walking shoes or court
shoes. Always wear cuffless trousers if you wear slip-on sandals. Never
wear protective gloves when pouring LN
2
or when putting the Dewar head on
the Dewar vessel. Just use an open flannel cloth (h) to protect your hands
from the cold. Gloves should be used only to grasp dry cold parts. They are
unsuitable for LN
2
work.
Only use metal Dewars specifically designated for storage of LN
2
, since only
containers of this kind exclude risks during storage. For routine cryopreparation
metal troughs (1 cm Styrofoam insulation), Styrofoam containers or plastic troughs
are eminently suitable and ensure low risk cryopreparation.
