Fig. 4.

Vacuum-based sampling recoveries from concrete. Total recoveries (A) and relative recoveries (B) for the vacuum sock (slow), vacuum sock (fast), 37 mm cassette filter (MCE), 37 mm cassette filter (PTFE), and forensic filter methods, achieved when used to sample inoculated concrete coupons. Relative recoveries were determined by dividing the mean number of spores recovered by each vacuum method by the mean number of spores recovered by wipe sampling stainless steel positive control coupons. All data are presented as the mean ± one standard deviation from ten replicate test samples, and five replicate positive control samples.