Dust And Pollution Control; Metallic Particulate Contamination - HP rp8400 Series Manual

Electrical and Environmental Guidelines
Environmental Elements

Dust and Pollution Control

Computer equipment can be adversely affected by dust and microscopic particles in the site environment.
Specifically, disk drives, tape drives, and some other mechanical devices can have bearing failures resulting
from airborne abrasive particles. Dust may also blanket electronic components like printed circuit boards
causing premature failure due to excess heat and/or humidity build up on the boards. Other failures to power
supplies and other electronic components can be caused by metallically conductive particles, including zinc
whiskers. These metallic particles are conductive and can short circuit electronic components. Use every
effort to ensure that the environment is as dust and particulate free as possible. See the following heading
titled "Metallic Particulate Contamination" for additional details.
Smaller particles can pass though some filters and over a period of time, cause problems in mechanical parts.
Small dust particles can be prevented from entering the computer room by maintaining the air conditioning
system at a high static air pressure level.
Other sources of dust, metallic, conductive, abrasive, and/or microscopic particles can be present. Some
sources of these particulates are:
• Subfloor shedding
• Raised floor shedding
• Ceiling tile shedding
These particulates are not always visible to the naked eye. A good check to determine their possible presence
is to check the underside of the tiles. The tile should be shiny, galvanized, and free from rust.
The computer room should be kept clean. The following guidelines are recommended:
• Smoking—Establish a no-smoking policy. Cigarette smoke particles are eight times larger than the
clearance between disk drive read/write heads and the disk surface.
• Printer—Locate printers and paper products in a separate room to eliminate paper particulate problems.
• Eating or drinking—Establish a no-eating or drinking policy. Spilled liquids can cause short circuits in
equipment such as keyboards.
• Tile floors—Use a dust-absorbent cloth mop rather than a dry mop to clean tile floors.
Special precautions are necessary if the computer room is near a source of air pollution. Some air pollutants,
especially hydrogen sulfide (H2S), are not only unpleasant but corrosive as well. Hydrogen sulfide damages
wiring and delicate sound equipment. The use of activated charcoal filters reduces this form of air pollution.

Metallic Particulate Contamination

Metallic particulates can be especially harmful around electronic equipment. This type of contamination may
enter the data center environment from a variety of sources, including but not limited to raised floor tiles,
worn air conditioning parts, heating ducts, rotor brushes in vacuum cleaners or printer component wear.
Because metallic particulates conduct electricity, they have an increased potential for creating short circuits
in electronic equipment. This problem is exaggerated by the increasingly dense circuitry of electronic
equipment.
Over time, very fine whiskers of pure metal can form on electroplated zinc, cadmium, or tin surfaces. If these
whiskers are disturbed, they may break off and become airborne, possibly causing failures or operational
interruptions. For over 50 years, the electronics industry has been aware of the relatively rare but possible
threat posed by metallic particulate contamination. During recent years, a growing concern has developed in
computer rooms where these conductive contaminants are formed on the bottom of some raised floor tiles.
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Chapter 2