3
•
Lasting low relative humidity is likely to result in loose screws due to washer contraction, and
even electrostatic discharge (ESD), which causes the circuits to fail.
Table 2 Humidity requirements
Humidity Range
Operating humidity
10% to 95%, noncondensing
Storage humidity
5% to 95%, noncondensing
Cleanliness
Dust buildup on the chassis might result in electrostatic adsorption, which causes poor contact of
metal components and contact points. In the worst case, electrostatic adsorption can cause
communication failure.
Table 3 Dust concentration limit in the equipment room
Substance
Concentration limit (particles/m
3
)
Dust particles
≤
3 x 10
4
(No visible dust on desk in three days)
NOTE:
Dust particle diameter
≥
5 µm
The equipment room must also meet limits on salts, acids, and sulfides to eliminate corrosion and
premature aging of components, as shown in
Table 4 Harmful gas limits in an equipment room
Gas Max.
(mg/m
3
)
SO
2
0.2
H
2
S 0.006
NH
3
0.05
Cl
2
0.01
NO
2
0.04
EMI
Electromagnetic interference (EMI) might be coupled from the source to the gateway through the
following coupling mechanisms:
•
Capacitive coupling
•
Inductive coupling
•
Radiative coupling
•
Common impedance coupling
•
Conductive coupling
To prevent EMI, take the following actions:
•
Filter interference from the power grid.
•
Keep the gateway grounding facilities away from grounding and lightning protection facilities of
other devices.
