University of Colorado Researchers: "Contrary to Purpose, Many Contents Expelled Outside"
Droplets Ejected at 2m/s Reach 1.5m Height Within 8 Seconds
Droplets ejected when flushing a toilet. Photo by Patrick Campbell / University of Colorado Boulder, provided by Yonhap News Agency
[Asia Economy Reporter Bang Je-il] A scientific experiment video has been released showing that the amount of invisible tiny droplets ejected inside the toilet bowl when flushing is much more severe than previously thought.
On the 8th (local time), an engineering research team at the University of Colorado Boulder in the United States used a green laser to visualize droplets splashing outside the toilet bowl when flushing, analyzing their speed and diffusion range, and published the results and video in the scientific journal Scientific Reports.
It was already confirmed over 60 years ago that droplets ejected when flushing toilets can carry various pathogens such as E. coli and norovirus. However, this is the first time it has been visually presented.
This study was conducted using a lidless cylinder flush-type toilet commonly used in public restrooms in North America. The research team irradiated the area above the toilet with two lasers to measure the speed and direction of droplets splashing outside the toilet bowl.
As a result, droplets were ejected at a speed of 2 meters per second and reached a height of 1.5 meters within 8 seconds. Among these droplets, heavier ones settled on surfaces within seconds, but particles smaller than 5 ㎛ (micrometers; 1㎛ = one-millionth of a meter) were found to remain suspended in the air for several minutes. The droplets mainly ejected upwards toward the back wall, but after reaching the ceiling, they also spread forward.
The research team stated, "This experiment did not involve feces or toilet paper," and predicted that "in actual public restroom environments, the droplet problem would be even worse." They also pointed out, "Although toilet bowls are designed to effectively remove waste, they are playing a role completely opposite to this purpose by ejecting a large amount of contents outside."
John Crimaldi, the first author of the paper and operator of the Ecological Fluid Dynamics Lab, said, "This study showed that droplets from toilet water are ejected and spread much more strongly than people realize," adding, "Once you watch the experiment video, you will never think about flushing the toilet the same way again."
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