Page 86 - The Veterinary Laboratory and Field Manual 3rd Edition

The selection, use, maintenance and quality control of laboratory equipment and supplies 55

uses the physics of water to store energy, thus
not relying on batteries. 1
Cold rooms are mainly used in bigger labora-
tories (Figures 2.12 and 2.13). If larger amounts
of samples need to be stored and/or samples
have to be kept for a longer period of time, it
might be useful to have a cold room.

Cooling units used in the field

convEntIonaL cooL boxES
Most of the time, conventional cool boxes with
cool packs are used in the field to preserve sam-
ples at a lower temperature. Cool boxes can be
used to keep items between 2–8°C or at –20°C.

• Between 2–8°C: cool packs (wet ice) are
stored in a freezer at –20°C. When preparing
a cool box that is to keep samples between
2–8°C, the frozen cool packs should be held
Figure 2.12 Cold room 1. Photo: Willy Schauwers,
Provincial Institute for Hygiene, Antwerp, Belgium. under running tap water until the cool pack
content starts to defreeze (until the con-
tent of the frozen ice pack starts to liquefy).
Samples should usually be kept cool after
sampling. But, make sure there is no direct
contact between the cool packs and the sam-
ples. Direct contact might freeze the samples
and make them unfit for use in the labora-
tory (for example, haemolysed EDTA blood
due to freeze-damage to the red blood cells)
(Figure 2.14).
• At –20°C: the cool box is filled with frozen
ice packs. Or, instead of frozen cool packs
(wet ice), dry ice (frozen, solid carbon diox-
ide – CO ) can be used as cooling unit for a
2
cool box. Most cool boxes these days are dry-
ice compatible. Dry ice keeps items frozen,
not just cold (dry ice has a temperature of
–78.5°C). Dry ice does not make things wet
Figure 2.13 Cold room 2. Photo: Willy Schauwers,
Provincial Institute for Hygiene, Antwerp, Belgium. (like wet ice). When water goes from ice to
liquid it takes up less room. However, when
dry ice goes from a solid to a gas it takes up
significantly more room, building up pressure

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