Webasto Air Top 2000 ST B Installation Instructions Manual page 23

Combustion air inlet and exhaust lines
An attachment is required no further than 150 mm from the end of the
exhaust pipe to ensure that the angle of 90° ± 10° is achieved
Discharge direction almost vertical 90° ± 10°
Fig. 22: Exhaust pipe opening
Installation position
Only for ADR: The statutory regulation of ADR (Accord européen relatif
au transport international des marchandises dangereuses par route)
governing the routing of the exhaust line, part 9 para. 9.2.4.7, must be
adhered to.
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Air Top 2000 ST