Table 2. Limits for particulates and gases
Contaminant Limits
Reactive gases
Severity level G1 as per ANSI/ISA 71.04-1985
1
:
• The copper reactivity level shall be less than 300 Angstroms per month (Å/month ≈ 0.0039 μg/
cm
2
-hour weight gain).
2
• The silver reactivity level shall be less than 200 Å/month (Å/month ≈ 0.0035 μg/cm
2
-hour
weight gain).
3
• The reactive monitoring of gaseous corrosivity must be conducted approximately 5 cm (2 in.) in
front of the rack on the air inlet side at one-quarter and three-quarter frame height off the floor
or where the air velocity is much higher.
Airborne
particulates
Data centers must meet the cleanliness level of ISO 14644-1 class 8.
For data centers without airside economizer, the ISO 14644-1 class 8 cleanliness might be met by
choosing one of the following filtration methods:
• The room air might be continuously filtered with MERV 8 filters.
• Air entering a data center might be filtered with MERV 11 or preferably MERV 13 filters.
For data centers with airside economizers, the choice of filters to achieve ISO class 8 cleanliness
depends on the specific conditions present at that data center.
• The deliquescent relative humidity of the particulate contamination should be more than 60%
RH.
4
• Data centers must be free of zinc whiskers.
5
1
ANSI/ISA-71.04-1985. Environmental conditions for process measurement and control systems: Airborne
contaminants. Instrument Society of America, Research Triangle Park, North Carolina, U.S.A.
2
The derivation of the equivalence between the rate of copper corrosion growth in the thickness of the corrosion
product in Å/month and the rate of weight gain assumes that Cu2S and Cu2O grow in equal proportions.
3
The derivation of the equivalence between the rate of silver corrosion growth in the thickness of the corrosion
product in Å/month and the rate of weight gain assumes that Ag
2S is the only corrosion product.
4
The deliquescent relative humidity of particulate contamination is the relative humidity at which the dust absorbs
enough water to become wet and promote ionic conduction.
5
Surface debris is randomly collected from 10 areas of the data center on a 1.5 cm diameter disk of sticky
electrically conductive tape on a metal stub. If examination of the sticky tape in a scanning electron microscope
reveals no zinc whiskers, the data center is considered free of zinc whiskers.
Chapter 1. Introduction 9
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