The difference in key analyte yields between smoking machine employing the rotary and linear methods has long been tolerated on the basis that these are small under the ISO regime and within the limits of expected experimental variance. These differences are magnified under Canadian Intense conditions and give rise to concerns that machines using the rotary principle for smoking have low NFDPM, water and TPM yields.

The influence of the essential difference in design of a remote capture pad has been investigated by eliminating other machine differences and “mimicking” the behaviour of the two different machine types on a single machine. Careful deconstruction of the smoke path has shown that the “dead volume” in a rotary system is both greater than a linear system and significant in determining the apparent yield. Moreover this effect is exacerbated by using the CI regime through a change in the smoke matrix formed. The relationship between regime conditions and dead volume has been investigated and an empirical relationship derived.

The relationship between puff volume and vapour desorption is identified as a secondary mechanism for lowering yields and is the subject of a separate paper.

The hazards inherent in using a remote capture pad and the consequences for CI smoking are made clear. Recommendations for design changes that minimise the apparent lowering of yields are presented.