Cabin Air Filter / Purifier: Description and Operation

MICROFILTERS







Microfilters are used in BMW climate control systems, this includes all vehicles produced after 9/91 (except E30). In addition, all E31 vehicles have been equipped with microfilters since start of production.

Shown in the above example is an E38 microfilter and location. Fresh air is continuously filtered through the microfilters. Never operate an E38 without the microfilters installed, there is the danger of water being drawn into the heater and/or damage to the electrical system.

The microfilter is designed to trap potentially irritating types of particles with very high efficiency. Some examples include:

- Pollens
- Spores
- Dust
- Vapors
- Floating air pollution
- Bacteria
- Viruses

Under normal operating conditions the microfilter(s) should be replaced every Inspection I and II (also every Oil Service 99 MY), except for M roadster or M coupe. The actual service life of the microfilter depends on the amount of contaminant and air flow rate reduction complaint, therefore; the replacement interval may be more frequent in dusty operating conditions.

E38 models have additional filters for the recirculation air inlets which require replacement at every second inspection II.