Ever since 1991, when the new ISO-standards were reviewed, ambient air flow around cigarettes in routine analytical smoking machines has become a more important factor to minimize variations in smoke yields and to obtain better repeatability and reproducibility. The air velocity shall be set at the standard value at least daily. If required it should be adjusted to the standard air velocity at the reference point within the smoking machine. In practical work, however, this can lead to difficulties caused by differences in constructions of laboratories, ventilation systems, fans etc. This paper will describe the components needed to obtain an air flow system that reaches such a degree of reliability that it reduces most of the practical labour in measurements and adjustments to keep the conditions within stated limits. The stability obtained with this system will be discussed. The paper will also present a ventilation system and the adjustments of linear smoking machine hood necessary to accomplish the improvements.