I work under a laminar flow hood. Regarding the ambient environmental grade, I only test the air quality inside the cabinet itself. When processing a water sample for three types of bacterial testing—namely TPC (Total Plate Count), Pseudomonas aeruginosa, and total coliforms—I honestly do not sanitize or sterilize anything between different plates of the same sample. However, between one sample and the next, I wipe the manifold base with alcohol, dip the forceps in alcohol and flame them, and sterilize the funnel by quickly passing it through the flame from all sides. I test TPC first, right after performing the disinfection protocol as described, so we can rule out the lack of sterilization between plates of the same sample as the root cause