Public restrooms are often avoided for various reasons, but a new study might add another to the list: toilet plumes. Researchers at the University of Colorado Boulder used lasers and cameras to visualize the spray ejected from a flushing commercial toilet, revealing a surprisingly energetic and rapidly spreading plume.
This isn’t news that toilets spray aerosolized particles of water, fecal matter, and even viruses like COVID-19 into the air upon flushing. However, this research, published in Scientific Reports, provides a stark visual representation of this phenomenon. The study, titled “Commercial toilets emit energetic and rapidly spreading aerosol plumes,” sheds light on the dynamics of this often-overlooked health concern.
Photo: John CrimaldiPhoto: John Crimaldi
“People have known that toilets emit aerosols, but they haven’t been able to see them,” explained John Crimaldi, the study’s lead author and an engineering professor at the University of Colorado, in a press release. Crimaldi, who heads the Ecological Fluid Dynamics Lab at the university, added, “We show that this thing is a much more energetic and rapidly spreading plume than even the people who knew about this understood.”
Illuminating the Plume with Lasers
Crimaldi and his team utilized continuous and pulsed lasers to create a thin, vertical sheet of bright green light directed at the toilet. This laser sheet illuminated the aerosol spray immediately following a flush, allowing the researchers to capture its movement and characteristics.
The Energetic Jet: Speed and Height
The researchers described the spray as a “strong chaotic jet” capable of reaching a height of nearly 5 feet (1.5 meters) within 8 seconds of flushing. The plume’s peak velocity was measured at 6.6 feet (2 meters) per second. The study analyzed the behavior of different particle sizes within the plume.
Particle Size and Linger Time
Larger particles, around 5 to 10 micrometers (roughly the size of a red blood cell), fall out of the plume more quickly. Smaller particles, however, can remain suspended in the air for longer periods, eventually settling on bathroom surfaces. This poses a potential health risk as these particles can carry bacteria and viruses.
Photo: John Crimaldi
Implications for Public Health
Crimaldi emphasized the importance of visualizing this phenomenon: “If it’s something you can’t see, it’s easy to pretend it doesn’t exist. But once you see these videos, you’re never going to think about a toilet flush the same way again.” He believes the study’s visual documentation can significantly impact public health messaging regarding restroom hygiene.
The study highlights the need for improved sanitation practices and ventilation in public restrooms to minimize the spread of airborne particles from toilet plumes.
