The widely used rule of staying 2 meters away from others does little to affect the risk of exposure to COVID-19 in indoor spaces, a new study shows.

Iran Press/America:  According to MIT researchers, the rule is based on an outdated understanding of how the coronavirus moves in closed spaces.

They said other variables - like the number of people in a space, whether they wear masks, what they are doing, and the level of ventilation - were much more important.

The 2-meters rule is used in various forms around the world: The Centers for Disease Control and Prevention advises 6 feet of separation indoors and outdoors, while in the UK the figure is 2 meters. In much of Europe, the figure is 1 meter, which is also recommended as a minimum distance by the World Health Organization.

But while such distancing rules are easy to remember, and purport to suit any situation, the new study says they may not be that useful.

The study was released online ahead of its publication in the peer-reviewed journal PNAS on Tuesday.

It says a better way of controlling indoor exposure is to do individual calculations based on variables for that space.

In some cases, the exposure level might be the same at 6 feet as at 60 feet, one of the study authors has said.

Scientific understanding of how the coronavirus moves in the air has challenged earlier assumptions about how best to adapt to minimize its spread.

At the beginning of the pandemic, it was widely believed that the virus traveled via heavier droplets ejected during exhalation, sneezing, or speaking.

But evidence has long suggested that the virus instead floats around on lighter aerosol droplets that can stay suspended in the air and travel much farther than first thought.

In their calculation, the MIT researchers took into account the effect of having people in the room, and their behavior, on how long the virus would stay suspended in the air.

In a calm environment, these particles would slowly drift to the ground, the researchers said in their study.

But in an environment in which the air is moving around the room and people are talking, eating, singing, and sneezing, the drops can be suspended in the airflow and mixed throughout the room longer.

The effect can be counteracted by ventilation or filtration to get the virus particles out of circulation in the room.

A website made available by the researchers shows how this model works in different scenarios.