A public toilet with poor ventilation is dangerous

Covid-19: public toilets more risky if ventilation is poor

Some studies have highlighted the risk of transmission from urine and feces

In times of Covid-19, flushing a public toilet, where ventilation is poor or inadequate, may create a risk of contagion: large quantities of aerosols, containing pathogens, could be generated.

A team of scientists from Florida Atlantic University’s College of Engineering and Computer Science has tested the physics of fluids and has investigated droplets generated from flushing a toilet and a urinal in a public restroom under normal ventilation conditions.

It is well known that saliva droplets emitted by breathing are the most important source of transmission of Covid-19, but some studies have also highlighted the risk of transmission from urine and feces. And in the new study, researchers evaluated the amount of droplets generated by flushing a toilet and urinal in a public bathroom under normal ventilation conditions, using a particle counter placed at various heights from the toilet. According to the research team's findings, public restrooms could serve as hotbeds for airborne disease transmission, especially under inadequate ventilation conditions.

The scientists considered three different scenarios, analyzing the concentration of particles and their movement in case of classic flushing, or flushing water with the toilet seat down and in urinal. The researchers measured the levels of aerosols and their ability to reach greater or lesser heights. The team tested toilets and urinals for 300 seconds, flushing the toilet five times at differentiated time intervals of 30, 90, 150, 210 and 270 seconds.

According to the scientists toilet and urinal generated large amounts of droplets less than three micrometers in size which pose a significant transmission risk if infectious microorganisms are present. Due to their small size, moreover, these droplets can remain suspended in the air for a long period of time.

Scientists detected the presence of aerosols up to 5 feet away and for periods of time longer than 20 seconds after the chain had been pulled. Despite the possibility of droplets escaping from the spaces between the tablet and the lid, the risk of particle spread was found to be diminished when runoff occurred with the lid down.

This work suggests the importance of implementing ventilation systems in enclosed and confined spaces such as public restrooms and to use toilet seat covers, to avoid the transmission of various infectious diseases in confined and poorly ventilated spaces.