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2-2
Especially when the indoor relative humidity is low, electrostatic adsorption is more likely to happen.
This can not only shorten the service life of your device but also cause communications failures. The
following table lists the dust concentration limit.
Table 2-1 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: The dust diameter is greater than or equal to 5 μm.
Besides dust, there are rigorous limits on the content of harmful substances in the air that can
accelerate the corrosion and aging of metals, such as chloride, acid, and sulfide in the equipment room.
The equipment room must be protected against ingression of harmful gases such as SO
2
, H
2
S, NH
3
,
and Cl
2
. For specific requirements, see the following table.
Table 2-2 Harmful gas limits 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
Electromagnetic Susceptibility
The operation of your switch can be affected by external interferences, such as conducted emission by
capacitance coupling, inductance coupling, electromagnetic wave radiation, and common impedance
(including the grounding system) coupling, and leads (power cables, signaling cables and output wires).
To eliminate the interferences, pay attention to the following:
z As the AC power system is a TN system, use a single-phase three-wire power socket with a
protection earth (PE) to effectively filter interference from the power grid.
z Keep the device far away from radio transmitting stations, radar stations, and high-frequency
devices.
z Use electromagnetic shielding, for example, shielded interface cables, when necessary.
z Route interface cables only indoors to prevent signal ports from getting damaged by over-voltage
or over-current caused by lightning strikes.
Laser Safety
The 3Com Baseline Switch 2900 Family are Class 1 laser devices.