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few minutes without the air filter in place. For maintenance instructions, see
“Maintaining the Air Filter” on page 68.
Maintaining Cooling System Components
This section discusses the following topics:
■ Maintaining the Air Filter on page 68
■ Maintaining the Fan Tray on page 68
Maintaining the Air Filter
A dirty air filter restricts airflow in the unit, producing a negative effect on the
ventilation of the chassis. The filter degrades over time. Periodically replace the filter
in use, as well as spares. We recommend that you replace the filter every 6 months.
For procedures to replace the air filter, see “Replacing the Air Filter” on page 94.
CAUTION: Always keep the air filter in place while the router is operating. Because
the fans are very powerful, they could pull small bits of wire or other materials into
the router through the unfiltered air intake. This could damage the router components.
Use spare filters within one year of manufacture. Check the date of manufacture
printed on the filter. Store spare air filters in a dark, cool, and dry place. Storing air
filters at higher temperatures, or where they can be exposed to ultraviolet (UV)
radiation, hydrocarbon emissions, or vapors from solvents, can significantly reduce
their life.
Maintaining the Fan Tray
The fan tray contains multiple fans that work in unison to cool the router components.
If one fan fails, the host subsystem adjusts the speed of the remaining fans to maintain
proper cooling. A red alarm is triggered when a fan fails, and a yellow alarm and red
alarm is triggered when a fan tray is removed.
To display the status of the cooling system, issue the show chassis environment
command. The output is similar to the following:
user@host> show chassis environment
Class Item Status Measurement
Temp PEM 0 OK 45 degrees C / 113 degrees F
PEM 1 OK 45 degrees C / 113 degrees F
PEM 2 Absent
PEM 3 Absent
68 ■ Maintaining Cooling System Components
MX240 Ethernet Services Router Hardware Guide