To Close or Not to Close?

The COVID-19 pandemic brought a renewed focus on hygiene, including the question of whether closing the toilet lid before flushing is more hygienic. A team of researchers from Japan's National Institute of Advanced Industrial Science and Technology (AIST) investigated this question through a series of experiments.

Their study involved installing a toilet bowl in a sealed booth and analyzing the spread of droplets and aerosols (tiny airborne particles) during flushing with the lid open and closed.

Droplets flew up to 40-50 centimeters and then fell.

Aerosols remained suspended in the air for several tens of minutes.

Particle measurements revealed a wide spread of aerosols, reaching 40 cm above the bowl and 15 cm in front of it.

Aerosol leakage to the upper part of the toilet was significantly reduced.

However, some aerosols leaked out towards the front, likely due to air displacement by the water flow.

To minimize this leakage, the researchers recommend a minimum distance of 15 cm between the toilet and the closed lid.

Using simulated viruses, the researchers found that about one-third adhered to the walls and underside of the toilet seat when the lid was closed.

They recommend wiping these surfaces along with the bowl during cleaning.

The researchers concluded that closing the toilet lid before flushing appears to be more hygienic, as it reduces the spread of aerosols and viruses. However, they emphasize that Japanese toilets are generally well-maintained for hygiene, and even without a lid or with the lid open, there is no need for excessive worry.

Maintain a distance of at least 15 cm between the toilet and the closed lid.

Wipe down the walls and underside of the toilet seat along with the bowl during cleaning.

Be mindful of hygiene practices in public restrooms.

This research provides valuable insights into toilet hygiene and can help individuals and facility managers make informed decisions to promote a cleaner and healthier environment.