The Petri Dish Test Kit is used for testing bacterial content on surfaces. This kit is ideal for pre and post testing of contaminated areas. Simply draw a sample from duct work, vents, filters, etc. Within 24 to 48 hours growth will appear. Then, treat the contaminated area with an RGF Turbozone® and draw another sample. Little or no growth should be evident, indicating successful treatment. (Dishes come in a pack of 12)