Test vials incubated for less than 24 hours do not have sufficient time for bacterial growth or colour change based on the pre-determined test limit of 200 cfu/mL. Test vials need a minimum of 24 hours to show accurate results for the limit of 200 cfu/mL. The longer you leave your vials in the incubator, the more sensitive the limit will become—meaning the vials will always detect bacteria and biofilm, however at levels lower than 200 cfu/mL.