Two methods of sampling high molecular weight vapours, gas syringe sampling and porous polymer adsorbent sampling were studied. The methods were compared using a saturated naphthalene reference vapour of known concentration. The results showed that the porous polymer adsorbent method was more accurate than the gas syringe method. The accuracies of both methods were dependent on details in their respective techniques. For porous polymer adsorbents it was shown that the technique should be such that passive sampling did not occur. Sample volume, sampling rate, the number of fills before injecting and cleaning the syringe before sampling all influenced the accuracy of the gas syringe sampling method.