Operator Activity; Hardware Movement; Outside Air; Stored Items - Oracle StorageTek SL3000 System Assurance Manual

It must be able to migrate to areas where it can cause the physical damage.
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The only differences between a potential contaminant and an actual contaminant
are time and location. Particulate matter is most likely to migrate to areas where it
can do damage if it is airborne. For this reason, airborne particulate concentration
is a useful measurement in determining the quality of the computer room
environment. Depending on local conditions, particles as big as 1,000 microns can
become airborne, but their active life is very short, and they are arrested by most
filtration devices. Submicron particulates are much more dangerous to sensitive
computer hardware, because they remain airborne for a much longer period of
time, and they are more apt to bypass filters.

Operator Activity

Human movement within the computer space is probably the single greatest source of
contamination in an otherwise clean computer room. Normal movement can dislodge
tissue fragments, such as dander or hair, or fabric fibers from clothing. The opening
and closing of drawers or hardware panels or any metal-on-metal activity can produce
metal filings. Simply walking across the floor can agitate settled contamination
making it airborne and potentially dangerous.

Hardware Movement

Hardware installation or reconfiguration involves a great deal of subfloor activity, and
settled contaminants can very easily be disturbed, forcing them to become airborne in
the supply air stream to the room's hardware. This is particularly dangerous if the
subfloor deck is unsealed. Unsealed concrete sheds fine dust particles into the
airstream, and is susceptible to efflorescence -- mineral salts brought to the surface of
the deck through evaporation or hydrostatic pressure.

Outside Air

Inadequately filtered air from outside the controlled environment can introduce
innumerable contaminants. Post-filtration contamination in duct work can be
dislodged by air flow, and introduced into the hardware environment. This is
particularly important in a downward-flow air conditioning system in which the
sub-floor void is used as a supply air duct. If the structural deck is contaminated, or if
the concrete slab is not sealed, fine particulate matter (such as concrete dust or
efflorescence) can be carried directly to the room's hardware.

Stored Items

Storage and handling of unused hardware or supplies can also be a source of
contamination. Corrugated cardboard boxes or wooden skids shed fibers when moved
or handled. Stored items are not only contamination sources; their handling in the
computer room controlled areas can agitate settled contamination already in the room.

Outside Influences

A negatively pressurized environment can allow contaminants from adjoining office
areas or the exterior of the building to infiltrate the computer room environment
through gaps in the doors or penetrations in the walls. Ammonia and phosphates are
often associated with agricultural processes, and numerous chemical agents can be
produced in manufacturing areas. If such industries are present in the vicinity of the
data center facility, chemical filtration may be necessary. Potential impact from
Contaminant Properties and Sources
Controlling Contaminants B-3