Gas and particulate exposure
Table 19. Gas and particulate exposure
Contamination Requirement
Gaseous contamination Severity level G1 as per ANSI/ISA 71.04-1985
1
, which states that the reactivity rate
of copper coupons shall be fewer than 300 Angstroms per month (Å/month, ≈
0.0039 µg/cm² - hour weight gain)
2
. In addition, the reactivity rate of silver coupons
shall be less than 300 Å/month (≈ 0.0035 µg/cm² - hour weight gain)
3
. The reactive
monitoring of gaseous corrosivity should 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.
Particulate
contamination
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 the choice of the following îš³ltration:
• The room air might be continuously ltered with MERV 8 lters.
• Air entering a data center might be ltered with MERV 11 or preferably MERV 13
îš³lters.
For data centers with airside economizers, the choice of îš³lters to achieve ISO class 8
cleanliness depends on the speciîš³c conditions present at that data center. The
deliquescent relative humidity of the particulate contamination should be more than
60% RH.3
4
.Data centers must be free of zinc whiskers
5
.
Notes:
1. ANSI/ISA-S71.04. 1985. Environmental conditions for process measurement and control systems: Airborne
contaminants, Instrument Society of America, Research Triangle Park, NC, 1985.
2. The derivation of the equivalence between the rate of copper corrosion product thickness growth in Ã…/
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 product thickness growth in Ã…/month
and the rate of weight gain assumes that Ag2S 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 2. Planning 27
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