3com 8807 User Manual

Dust is a hazard to the operating safety of the switch. The indoor dust 
accumulated on the chassis can cause electrostatic absorption, which may result in 
the poor contact of the connector or metal contact point. This happens more 
frequently when indoor relative humidity is low, which will not only shorten the 
service life of the switch, but also cause communication failure.

The required specifications on dust content and particle diameter in an equipment 
room are shown in the following table.

Besides the dust specifications, the equipment room of the switch should also 
meet the rigorous requirements for the content of salt, acid and sulfide in the air. 
These harmful gases could accelerate the metal erosion and the aging process of 
some parts. Incursion of harmful gases, such as SO

2

, H

2

S, NO

2

, NH

3

, and Cl

2

, 

should be prevented. The specific limitation values of these harmful gases are 
given in the following table.

Any possible interference sources, no matter outside or inside the system, affect 
the switch in use in a way of capacitive coupling, inductive coupling, 
electromagnetic radiation, common impedance (including the grounding system) 
coupling or conducting line (power line, signaling line and transmission line etc.). 
To prevent the interference, you should:

■

Take effective measures against electrical net interference for power supply 
system.

■

Separate the working ground of the switch from the grounding device of the 
power supply equipment or lightning-protection grounding device as far as 
possible.

■

Keep the switch far away from the radio launcher, radar launcher, and 
high-frequency devices working in the high current.

■

Adopt electromagnetic shielding if necessary.

A good grounding system is not only the basis essential to the stable and reliable 
switch operation, but also an important guarantee of lightning protection, 
anti-interference and ESD-prevention. The user must provide good grounding 
system for the switch.

Table 68   Limitation on dust content in equipment room

Dust particle 

particles/m

3

‚

≤

3 x 10

4

(No visible dust on desk in three days) 

Note: Dust particle diameter ‚

≥

 5µm

Table 69   Harmful gas limits in an equipment room

SO

2

 

0.3 

1.0 

H

2

S 

0.1 

0.5 

NO

2

 

0.004 

0.15 

NH

3

 

1.0 

3 

Cl

2

 

0.1 

0.3