For each 'FFR model/decontamination treatment' combination, the average initial filter airflow resistances are summarized in Table 3 . The six FFRs in which melting occurred could not be tested for filter airflow resistance. For the remaining 129 postdecontamination samples tested, average initial filter airflow resistance measurements were 17.0 mm H 2 O. Previous studies using the same test method on 21 models of NIOSH-approved N95 FFRs observed filter airflow resistance levels between 7 and 30 mmH 2 O . For filter airflow resistance, three of the nine ANOVA tests, including N95-B (P 5 0.0035), SN95-D (P 5 0.0170), and SN95-F (P 5 0.0014), showed significantly different means (see Table 4 ). Although statistically significant, the levels of differences in filter airflow resistance between treatments are not practically meaningful as small changes in filter airflow resistance are unlikely to be noticed by the user (Vojtko et al., 2008) . 