*3.2. Estimation of Emission Rates (ERs) on 'Heating Mode'*

Estimated VOC emission rates from the investigated items on 'heating mode' are listed in Table 3. They were estimated starting from the emission rate values derived for 'not-heating mode' through 72-hour test chamber experiments and taking into account the GC-MS peak area ratios obtained by dynamic head-space investigations, performed both for 'not-heating mode' and 'heating mode'. Overall, as expected, the high temperature acquired during the heating process affected VOC emissions behavior from all the investigated bags. From a lesser to greater extent, the emission process of the selected VOCs was promoted. With specific regard to the 'polyester-brand A' bag, the GC-MS peak area ratios suggest that naphthalene was the most sensitive compound to the temperature change. The estimated naphthalene emission rate when the bag was on 'heating mode', indeed, was revealed to be 70 times higher than the calculated emission rate on 'not-heating mode', with a variation from 9013 ng/h to 630.9 μg/h. For all the other VOCs, the estimated emission rates ranged from a minimum value of 0.20 μg/h for benzene to a maximum value of 6.79 μg/h for toluene. From the comparison of HS experimental data reported in Table 3, it is possible to observe that the estimated emission rates for the VOCs of concern emitted by 'PVC-brand B' and 'PVC-brand C' were generally lower compared with those estimated for 'polyester-brand A'. This evidence is not related to temperature because the effect of heating on the emission process is comparable for all the three investigated bags, with peak area ratios of the same order of magnitude. It is, instead, attributable to the starting values of emission rates for 'PVC-brand B' and 'PVC-brand C' calculated from test chamber experiments being generally lower than those for 'polyester-brand A'. More specifically, estimated emission rates for 'PVC-brand B' and 'PVC-brand C' on 'heating mode' were in the range 0.11–11.2 μg/h and 0.03–2.9 μg/h, respectively. Similarly to 'polyester-brand A', the increase in temperature significantly affected the naphthalene emission from 'PVC-brand B', resulting in an estimated emission rate on 'heating mode' 109 times higher with respect to 'not-heating mode' (with an increase from 113 ng/h to 11.2 μg/h). The remarkable effect of the high temperature on the naphthalene emissions observed for both 'polyester-brand A' and 'PVC-brand B' but not for 'PVC-brand C' may be explained by taking into account the different surface treatments. The 'polyester-brand A' and 'PVC-brand B' bags, indeed, had an external coverage characterized by an image applied onto the surface. On the contrary, the coverage of 'PVC-brand C' was only colored. The surface treatment for image application may be responsible for the higher naphthalene emission rates both on 'heating mode' and 'not-heating mode' because it is known, as highlighted above, that naphthalene is used for the production of plasticizers and dyes. Moreover, the use of naphthalene in surface treatment to preserve the items from any kind of deterioration during long-range transport cannot be excluded, i.e., naphthalene used as a repellent for undesired insects or as anti-mold. As regards all the other VOCs, taking into account the peak area ratios representing the effect of the heating process on emission behavior, it is reasonable to make the assumption that the high temperature promoted the diffusion process of compounds through the polymeric bulk and, as a result, the emission from the surface. The emitted VOCs indeed seem to be incorporated in the polymeric structure as residues, and related contaminants of the solvents used in the polymer manufacturing process, unlike naphthalene, seem to be more abundant on the surface layer.


**Table 3.** Estimation of VOC emission rates (ERs, μg/h) for the investigated bags on 'heating mode'.
