You know that smell that tells you something is rotten or growing mold? That’s a by-product of biofilm. When biofilm has grown large enough to be seen, it is usually described as a congealed or gelatin-like substance with an unpleasant odor. This video helps to show how biofilms form. Pay careful attention to the segment that talks about how different bacteria live together, feeding off of each other’s off-gasses.
To date, heat is the best and most consistent enemy of biofilms, which account for the continual increase in either chemical strength or dwell time (or both) because biofilms are increasingly resistant to chemical intrusions.