C120-H007-08EN 43
4.3 Air Conditioning Conditions
4.3.4 Dust
(1) Airborne dust
Ensure that airborne dust does not exceed 0.15 mg/m
3
(0.004 mg/ft
3
). Most server
systems are designed to withstand this level of airborne dust. This is the same as the
permissible level for airborne dust in a general office and should be easily attainable
in a computer room where there is little inflow of outside air and smoke.
(2) Removing dust
Airborne dust is collected by air filters in the air conditioner. For air filter, see Section
4.5.2, "Air conditioner filters." The computer room must be periodically cleaned to
remove dust on and under the floor. For cleaning procedures, see (6), "Base floor and
free-access floor cleaning," in 2.3.2, "Free-access flooring."
Cleaning is required in the following situations:
When the construction of the computer room has just been completed, and it is
ready to house equipment.
When the computer room has been repaired.
When equipment already in position in the computer room has been relocated.
Areas surrounding printers and for forms handling require periodic cleaning.
4.3.5 Corrosive gases
Corrosive gases must be removed and kept out by using appropriate air cleaning
facilities. Maintaining positive pressure in the computer room with filtered air will
serve as a safeguard against the entry of corrosive gases or dust from an outside
source.
Table 4.4 lists the tolerable limits for different kinds of corrosive gases.
Table 4.4 Tolerable limits for corrosive gases (1/2)
Gas name Tolerable limit
Hydrogen sulfide (H
2
S) Up to 7.1 ppb
Sulfur dioxide (sulfur oxide) (SO
2
) Up to 37 ppb
Hydrogen chloride (HCI) Up to 6.6 ppb
Chlorine (CI
2
) Up to 3.4 ppb
Hydrogen fluoride (HF) Up to 3.6 ppb
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