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Exposure Points
The encapsulant must not out-gas any harmful contaminants. Many encapsulants
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commonly used in industry are highly ammoniated or contain other chemicals
that can be harmful to hardware. It is very unlikely that this out-gassing could
cause immediate, catastrophic failure, but these chemicals will often contribute to
corrosion of contacts, heads or other components.
Effectively encapsulating a subfloor deck in an on-line computer room is a very
sensitive and difficult task, but it can be conducted safely if appropriate procedures
and materials are used. Avoid using the ceiling void as an open supply or return for
the building air system. This area is typically very dirty and difficult to clean. Often
the structural surfaces are coated with fibrous fire-proofing, and the ceiling tiles and
insulation are also subject to shedding. Even before filtration, this is an unnecessary
exposure that can adversely affect environmental conditions in the room. It is also
important that the ceiling void does not become pressurized, as this will force dirty air
into the computer room. Columns or cable chases with penetrations in both the
subfloor and ceiling void can lead to ceiling void pressurization.
Exposure Points
Address all potential exposure points in the data center to minimize potential
influences from outside the controlled zone. Positive pressurization of the computer
rooms will help limit contaminant infiltration, but it is also important to minimize any
breaches in the room perimeter. To ensure the environment is maintained correctly,
consider the following:
Make sure all doors should fit snugly in their frames.
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Use gaskets and sweeps to address any gaps.
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Avoid automatic doors in areas where they can be accidentally triggered. An
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alternate means of control would be to remotely locate a door trigger so that
personnel pushing carts can open the doors easily. In highly sensitive areas, or
where the data center is exposed to undesirable conditions, it may be advisable to
design and install personnel traps. Double sets of doors with a buffer between can
help limit direct exposure to outside conditions.
Seal all penetrations between the data center and adjacent areas.
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Avoid sharing a computer room ceiling or subfloor plenum with loosely controlled
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adjacent areas.
Filtration
Filtration is an effective means of addressing airborne particulate in a controlled
environment. It is important that all air handlers serving the data center are
adequately filtered to ensure appropriate conditions are maintained within the room.
In-room process cooling is the recommended method of controlling the room
environment. The in-room process coolers re-circulate room air. Air from the hardware
areas is passed through the units where it is filtered and cooled, and then introduced
into the subfloor plenum. The plenum is pressurized, and the conditioned air is forced
into the room, through perforated tiles, which then travels back to the air conditioner
for reconditioning. The airflow patterns and design associated with a typical computer
room air handler have a much higher rate of air change than typical comfort cooling
air conditioners so air is filtered much more often than in an office environment.
Proper filtration can capture a great deal of particulates. The filters installed in the
in-room, re-circulating air conditioners should have a minimum efficiency of 40%
(Atmospheric Dust-Spot Efficiency, ASHRAE Standard 52.1). Install low-grade
pre-filters to help prolong the life of the more expensive primary filters.
F-6 StorageTek T10000 Tape Drive Operator's Guide
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