Webasto Air Top 3500 ST Installation Instructions Manual - page 20
Combustion air supply
Air Top 3500 ST / Air Top 5000 ST
52
8
Combustion air supply
Under no circumstances may the combustion air be taken from areas
occupied by people. The combustion air intake opening must not point
in the direction of travel. It must be located so that it cannot become
clogged with dirt.
NOTE:
An intake silencer must be fitted if the intake hose length is greater than
0.6 m.
NOTE:
The combustion air must be extracted using a combustion air line from
a position that is as cool as possible and protected from splashing water.
Do not use an exhaust line as the combustion air line since otherwise
the metering pump cable from the combustion air inlet port may be
damaged. The combustion air opening must not be under the minimum
water drive-through level permitted for the vehicle.
See the statutory regulations for the installation for further regulations.