The heated air ventilation on buses, foreseen with a Type 4 engine is contrary to Type 1 engines, actioned by an electrical blower that recovers the air taken in for the heating from the engine department and rush it through the heat exchangers into the inner compartment. The blower is located at the top of the engine compartment, from which 2 cardboard hoses lead to the heat exchangers. These cardboard hoses are very subject to wear, on the one hand due to vibrations and on the other hand to extreme fluctuations in temperature. From now on BBT can deliver these hoses as well as the correctly fitting seals each from stock.