FIG. 1.

Layout of the chamber and an example of method and laboratory sample assignment. The large (929 cm²) and small (103 cm²) squares indicate the locations of the test coupons (stainless steel or carpet). The circles (60 cm²) indicate the reference agar plate (A) locations. For each chamber run, the method (S, swab; W, wipe, and V, vacuum) and laboratory (1, 2, and 3) were randomly assigned to each square test coupon as described in the text.