5
• Lasting high relative humidity can cause poor insulation, electricity creepage, mechanical property
change of materials, and metal corrosion.
• Lasting low relative humidity can cause washer contraction and ESD and bring problems including
loose captive screws and circuit failure.
• High temperature can accelerate the aging of insulation materials and significantly lower the
reliability and lifespan of the switch.
For the temperature and humidity requirements of different switch models, see "Appendix A Chassis
v
iews and technical specifications."
Cleanness
Dust buildup on the chassis might result in electrostatic adsorption, which causes poor contact of metal
components and contact points, especially when indoor relative humidity is low. In the worst case,
electrostatic adsorption can cause communication failure.
Table 1 Dust concentration limit in the equipment room
Substance Concentration limit (particles/m³)
Dust
≤ 3 x 10
4
(no visible dust on the tabletop over three days)
NOTE:
Dust diameter ≥ 5 μm
The equipment room must also meet strict limits on salts, acids, and sulfides to eliminate corrosion and
premature aging of components, as shown in Table 2.
Table 2 Harmful gas li
mits in the equipment room
Gas Maximum concentration (mg/m
3
)
SO
2
0.2
H
2
S 0.006
NH
3
0.05
Cl
2
0.01
EMI
Electromagnetic interference (EMI) might be coupled from the source to the switch through the following
coupling mechanisms:
• Capacitive coupling
• Inductive coupling
• Radiative coupling
• Common impedance coupling
• Conductive coupling
To prevent EMI, take the following actions:
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