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During the pandemic, we’ve been encouraged to adhere to physical distancing in restaurants and office spaces to limit the spread of the virus.
The rule of thumb is at least two metres between each person, desk, or chair.
We’ve also been told that the risk increases in indoor spaces.
As the months have rolled on, scientists have been able to collect more data, leading to more accurate risk assessments.
Per Fast Company, John Bush, a professor of applied mathematics at MIT, says that the rules that we’ve been sticking too aren’t as effective as we thought they were.
Bush, alongside his MIT colleague Martin Z. Bazant, has created a complex mathematical model, which simulates the fluid dynamics of virus-loaded respiratory droplets in any space, from a small kitchen to a massive concert hall.
To make things simpler for those of us who die a little inside when confronted with mathematics in general, let alone the complicated kind, they converted their findings into an online tool that anyone can use to judge COVID-19 risk scenarios.
If you visit the website, you’ll fill out some basic information about your space.
The tool assumes one person in a room with you has COVID-19. Variables that you’ll fill in include:
What’s the square footage? What’s the height of the ceiling? How about the HVAC system—is it a standard domestic furnace or does it have a fancy HEPA filter? What’s the humidity? Is a window open?
The variables also include all sorts of details about human behavior: How many other people are there with you? Are they wearing masks? Cotton or surgical? Do they wear masks properly or pull them down their face a bit? Are they whispering or singing?
I took a random listing for a 467m² commercial property from a real estate website, with a 70m² open-plan office space which seats 35 people.
We’ll be using the open-plan office space with a standard air conditioning system to work things out. The room would be filled to capacity with employees who take their masks off and talk while working.
In other words, a standard office situation.
Room Specifications
Total floor area: 70m²
Ceiling height: 12 metres
Ventilation: Mechanical ventilation (air conditioning)
Filtration system: residential/commercial/industrial
Recirculation rate: moderate
Relative humidity: 60% (average)
Human behaviour
Exertion level: resting (at a desk)
Respiratory level: talking (normal)
Mask type: none (while in office) / surgical cotton.
Mask fit: none
Result:
Based on this model, it should be “safe” for this room to have:
- 2 people for 43 minutes
- 3 people for 26 minutes
- 4 people for 19 minutes
- 5 people for 16 minutes
- 10 people for 9 minutes
- 25 people for 5 minutes
- 50 people for 4 minutes or
- 100 people for 2 minutes.
The two-metre distancing guideline would indicate that up to one person would be safe in this room for an indefinite period.
To summarise, if this room has 35 people, its occupants would be safe for four minutes.
Those results are pretty terrifying.
You can then tweak the system to see if the results change, by, for example, changing ‘no masks’ to ‘cotton masks at all times’, or increasing the distance between employees.
Opening the windows to increase airflow also makes a difference:
Room Specifications
Total floor area: 70m²
Ceiling height: 12 metres
Ventilation: Open windows
Filtration system: Open windows with fans
Recirculation rate: moderate
Relative humidity: 60% (average)
Human behaviour
Exertion level: resting (at a desk)
Respiratory level: talking (normal)
Mask type: surgical cotton worn at all times
Mask fit: 95%
Result:
Based on this model, it should be safe* for this room to have:
- 2 people for 4 hours
- 3 people for 2 hours
- 4 people for 2 hours
- 5 people for 72 minutes or
- 10 people for 38 minutes.
The two-metre distancing guideline would indicate that up to one person would be safe in this room for an indefinite period.
If this room has 35 people, its occupants should be safe for 15 minutes.
The risk decreases with additional safety measures.
Obviously, this is just a model, but it is useful for determining the safest possible environment for the people entering a space.
It also doesn’t take into account sanitising measures and regular screening.
It’s a highly contagious virus, and it’s difficult to beat, but PPE and some regular handwashing, alongside quarantining if you feel that you’ve come into contact with an infected person, can go a long way towards keeping yourself and others safe.
You can tinker with that MIT tool here.
[source:fastcompany]
