Perform Lab Work Inside a Sterile Field
Light and Adjust Bunsen Burner
-After the alcohol used to sterilize the work surface has completely dried, use an ignitor to light the Bunsen burner
-Adjust the flame so that a blue cone can be seen in the middle of the flame
-Keep the Bunsen burner on during the entire procedure
-It can be helpful to demarcate the area within which to safely perform sterile work. To do so, place a 30 x 27 cm (12 x 10.75 inch) sheet of aluminum foil on the work surface, with the burner centered along the top edge
-Spray the foil with 70% isopropyl alcohol, wipe with a clean paper towel, and allow to dry before lighting the burner.
Work Inside the Sterile Field
-The flame produces an updraft or air convection current which rises up and away from the flame
-As heat rises, micro-organisms and dust particles are forced upward and away from the immediate work area, forming a sterile field that extends 30-40 cm (12-15 inches) around the permeter of the burner and approximately 10 cm (4 inches) above the flame
-To minimize contamination and maintain aseptic conditions, it is critical that handling of all media and samples be done within the sterile field
-In order to ensure sterile condintions, the lips of glass culture tubes and flasks should be passed through the tip of the blue cone, the hottest part of the flame, after opening and before closing
–Plastic tubes, flasks, and Whirl-Paks CANNOT BE FLAMED – these should be purchased pre-sterilized.