Chapter 2
General System and Facility Guidelines
Environmental Factors
35
CAUTION
Low humidity contributes to undesirably high levels of electrostatic charges. This increases the
electrostatic discharge (ESD) voltage potential. ESD can cause component damage during
servicing operations. Paper feed problems on high-speed printers are usually encountered in
low-humidity environments.
Low humidity levels are often the result of the facility heating system and occur during the cold season. Most
heating systems cause air to have a low humidity level, unless the system has a built-in humidifier.
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 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.
