much longer time (Wang et al. 1999). As previously mentioned, the complex structure of

bacterial spores protects cellular components by developing antimicrobial resistance, and low

concentrations of chemical germinants can cause the spores to germinate (Moir et al. 2002). A

study on the killing mechanism of spores by chemicals used in decontamination procedures

demonstrated that spores can germinate even after they are treated with nitrous acid, while those

treated with BetadineTM containing 1% available iodine do not germinate (Tennen et al. 2000).

Our study demonstrates such a benefit of incorporating iodine with filtration for biocidal

applications.

 Surviving microorganisms on filters can re-entrain into the air passing through the filter

medium, which has been reported in several studies (Qian et al. 1998; Wang et al. 1999;

Rengasamy et al. 2004). A study on the reaerosolization of bacteria and solid particles from N95

respirators observed that the reaerosolization of particles smaller than 1 |tm is insignificant (<

0.025%). Reaerosolization of larger aggregates of bacteria or bacteria attached to large inert

particles, however, is significant at the same reaerosolization velocities, which correlate with

violent sneezing and coughing, and at low (22%) RH (Qian et al. 1997). The reentrainment of

fungal spores was higher than that of KCl particles due to disaggregation of fungal spores.

Moreover, the rate is different among various fungal spore species depending on the surface

structure (Jankowska et al. 2000). The present study showed very low extraction (6.9x10-4

1.6x10-4) by vortexing. This value is much lower than that reported in a prior study for B.

subtilis from polycarbonate filters, where the vortexing method exhibited extraction efficiency of

85% (Wang et al. 2001). In other words, the spores were securely trapped in the filter matrix of

our test filters, resulting in inefficient extraction. This phenomenon is supported by the SEM

images shown in Figure 2-4. The bacterial spores are attached to the fibrous surface due to van