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Dry Heat sterilization should be used only
for materials that might be damaged by moist heat or that are
impenetrable to moist heat (e.g., powders, petroleum products, sharp
instruments).
The primary lethal process is considered to be oxidation of
cell constituents. The most common time-temperature relationships
for sterilization with hot air sterilizers are 170°C (340°F) for 60
minutes, 160°C (320°F) for 120 minutes, and 150°C (300°F) for 150
minutes.
Advantages and Disadvantages of Dry Heat Sterilization:
The advantages for dry heat include the
following: it is nontoxic and does not harm the environment; a dry
heat cabinet is easy to install and has relatively low operating
costs; it penetrates materials; and it is noncorrosive for metal and
sharp instruments. The disadvantages for dry heat are the slow rate
of heat penetration and microbicidal killing makes this a
time-consuming method. In addition, the high temperatures
are not suitable
for most materials.
Two
Types of Dry Heat Sterilizers:
There are two types of dry-heat sterilizers: the
static-air type and the forced-air type. The static-air type is
referred to as the oven-type sterilizer as heating coils in the
bottom of the unit cause the hot air to rise inside the chamber via
gravity convection. This type of dry-heat sterilizer is much slower
in heating, requires longer time to reach sterilizing temperature,
and is less uniform in temperature control throughout the chamber
than is the forced-air type. The forced-air or mechanical
convection sterilizer is equipped with a motor-driven blower that
circulates heated air throughout the chamber at a high velocity,
permitting a more rapid transfer of energy from the air to the
instruments. ATS, Inc. offers a quality line of Dry Heat
sterilizers – compare our
prices!
Spore Testing
Dry Heat Sterilizers:
Bacillus atrophaeus spores should be used to monitor the
sterilization process for dry
heat because they are more resistant to dry heat than are
Geobacillus stearothermophilus
spores.
Autoclave Testing Service, Inc. spore tests all
sterilizers, not just autoclaves (steam sterilizers). For spore
testing Dry Heat sterilizers, the microbiology laboratory uses
Bacillus atrophaeus spores which are cultured at 35°C. We offer
immediate notification of
positive
tests (spores that show growth indicating sterilizer
failure). Most failed tests show up within 24 to 48 hours and you
will be immediately notified. ATS, Inc. is also a supplier of Dry
Heat sterilizers – see
New or
Used sterilizers.
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