Health

Blue laser reveals you should close the toilet lid before flushing


Blue laser reveals you should close the toilet lid before flushing

The laboratory illuminates and photographs the aerosol beams produced by the water jet. (One) Lab tested with a flush-type commercial toilet (1.6 gallons per flush). For all experiments, toilets contained — and were flushed with — purified tap water with no solids or additives. The relief valve (located behind the rear wall) is powered by a 60 psi supply and is electrically actuated via a push button. (b) We use pulsed and continuous laser beams to create a thin strip of light that illuminates the beam in a vertical plane above the centerline of the bowl. (OLD) The laser light scattered by aerosol particles during and after the discharge cycle is recorded by the camera. (D.) Time history of flushing cycle intensity and duration using the average sound pressure level in the bowl (red line) from 20 discharge repetitions (gray line) as a measure. Time t=0 corresponds to the time of pressing the flush button. Credit: Scientific reports (2022). DOI: 10.1038/s41598-022-24686-5

Engineers at the University of Colorado Boulder have confirmed what the germ-fearing among us have long suspected: Commercial toilet flushes release a Vesuvius-like cloud of tiny droplets and sol particles. air 5 feet above the seat.

Although not visible to the naked eye, when illuminated with a green laser, the confetti cluster looks like a bunch of microscopic confetti thrown at the world’s grossest party, a bunch consisting of water droplets and anything else that might be in the bowl.

The study was published in December in the journal Scientific reportswhat a poll in fluid mechanics. The team only flushed the toilet with clean water and did not investigate the infectious potential of any particles that might be present in the water.

But their tools have confirmed that each flush reaches much further than the bowl most of us would like to believe.

“We were all amazed,” said John Crimaldi, lead author of the study. “I said, ‘Oh, my God – that’s what happens?”

Crimaldi is a professor of hydrology specializing in fluid mechanics—specifically, how air and water transportation other materials flow with it. He considered the ways ocean currents distribution of sperm and eggs to fertilize corals and how odorous particles travel through the air to transmit information to animals.

He turned his attention to toilets at the urging of colleague Boulder and co-author Karl Linden, an environmental engineer who studies the disinfecting properties of ultraviolet light.

While brainstorming about the ideal test case for a UV-based surface sanitizer, Linden’s mind first had to go to some dirty place.

“Where are we exposed to the virus and where are we exposed to the pathogen?” Linden said. “And one of my thoughts was, ‘Well, what’s going on in the toilet?'”

Linden is envisioning commercial toilets specifically: the barrelless, lidless horses found in public restroom stalls. Most public toilet in North America are equipped with what is known as a sump-type valve, which relies on pressure rather than gravity to push water through the bowl.

The result is a powerful jet of water that leaves behind a fluffy cloud of steam after it emerges—a smaller, less cheerful version of mist rising over each log as it descends Disneyland’s Splash Mountain one last time. .

Previous studies have confirmed that surfaces around public restrooms are often a breeding ground for fecal bacteria. UV light could be an effective disinfectant, Linden thinks – but first, he needs to better understand how microscopic pathogens travel through space.






On the left, nothing is visible to the naked eye. On the right, a powerful green laser helps visualize the jets of aerosols spewing from the toilet as it is being flushed. Credits: John Crimaldi

He turned to Crimaldi, whose lab uses lasers to visualize fluid movements that are invisible to the human eye. Crimaldi’s Fluid Mechanics Laboratory has traditionally spent a week every summer solving a small scientific challenge without funding or any pressure to publish. The toilet question is a perfect fit.

“We said, ‘Maybe nothing will happen, or maybe we’ll get something really great,'” Crimaldi said.

Instead of shipping their device to the nearest bathroom, the team installed a lab-operated toilet on a metal frame that could be aligned with their laser. They then calibrated the plumbing’s water pressure to match the water pressure of a typical commercial restroom.

They know their laser will make some aerosols visible. They were not prepared for the small explosion that greeted them on the first flush.

“It’s like an erupting volcano,” Crimaldi said. “Some of us were dumbfounded. Some of us just laughed in disbelief, and were like, ‘Oh my God, we’re really doing something here.'”

The team then trained a pulsed laser and a pair of scientific cameras on the aerosol to measure the speed of individual water particles. A flush in the toilet doesn’t have the speed of a sneeze, which can shoot up droplets at 100 miles per hour, or even a cough, the droplets can fly up to 50 miles per hour.

The aerosols in the plume were “surprisingly energetic and chaotic” reaching a maximum velocity of 2 meters per second, or just under 4.5 miles per hour, the study authors reported. However, once they are in the air, they take a while to settle back down. Nearly eight seconds after flushing, the particles were still suspended more than 5 feet from the edge of the bowl—much higher than nose level for most people. Many remained in the air for more than a minute.

“After watching these videos, I’m definitely more inclined to wear a mask in public restrooms than I used to be,” Crimaldi said.

Although the experiments were conducted with empty toilets but Clean waterCrimaldi strongly suspects that adding toilet paper and human waste to the mix only adds chaos and energy to the flush.

“I have an intuitive feeling that the presence of solids could exacerbate the problem as there are only more things for the water to collide with and create more opportunities for fluid mixing to overwhelm,” he said. this energy”.

Linden hopes to use this experiment as a starting point for future research to track the distances that bacteria and other pathogens travel within these aerosol clouds and the length of time they infect. Depending on those findings, “can we start thinking about what interventions we could use?” he say. “Several redesigns of a toilet that we might want to look at?”

Advocates of alternatives to flush toilets say the study strengthens the argument for finding better methods of disposing of human waste.

Bryn Nelson, a microbiologist and author of the book “Drainage: The Remarkable Science of an Uncertain Treasure.”

“Many composting toilets use vacuums and little or no water, so this could be another reason to consider the value of these eco-friendly models.”

More information:
John P. Crimaldi et al, Commercial toilets that emit energetic and fast-spreading aerosols, Scientific reports (2022). DOI: 10.1038/s41598-022-24686-5

2022 Los Angeles Times.

Distributed by Tribune Content Agency, LLC.

quote: Green laser reveals you should close toilet lid before flushing (2022, Dec 29) retrieved Dec 29, 2022 from https://medicalxpress.com/news/2022-12-green- lasers-reveal-toilet-lid.html

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