423 Pa (at 14.2 cm/s) and was maintained throughout the entire experiment with almost
negligible variation. There was no observable difference in pressure drop between the iodine-
treated and untreated filters.
Survival Fraction
To determine the viability of the collected spores, both iodine-treated and untreated filters
were vortexed to extract spores from the filters. A larger number of spores extracted from the
untreated filter was enumerated than from the iodine-treated filter at RT/LRH. No increase of
extracted spores from the test filters was observed as the vortexing time increased. Although
both survival fractions were low, the survival fraction of the iodine-treated filter was
significantly lower than that of the untreated filter, which was confirmed by t-test (p-value
< 0.05). At RT/HRH and HT/HRH, the survival fraction of the iodine-treated filter showed
around one log unit higher value than that at RT/LRH. This higher survival fraction can possibly
be explained by the loss of iodine from the filter due to increased sublimation of iodine at HT
and dissolution through the hydrolysis of iodine at HRH. To test this hypothesis, we measured
the iodine concentration in the vortexing solution of the iodine-treated filter by the DPD
colorimetric method. The values (mg I2/L) at RT/HRH (0.400.03) and HT/HRH (0.300.03)
were lower than that at RT/LRH (0.900.03). Statistical significance between RT/LRH and the
others was observed by performing one-way ANOVA (p-value < 0.05). Meanwhile, the
difference between RT/HRH and HT/HRH was not significant (p-value > 0.05). We note that n
is small (i.e., 2) and measurement uncertainty of survival fractions is large at both RT/HRH and
HT/HRH.
To investigate the effect of residual free iodine in the vortexing solution on the survival
fraction of the extracted spores, spores were inoculated into the solution after vortexing a clean