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Finally sun again, finally coming out again. But with a year of experience in a pandemic, little by little we are all beginning to know: outside is better than inside.
Of course, the rules also apply outdoors. How much care do we have to be careful outside so as not to get infected?
We wanted to hear from Christof Asbach, aerosol researcher at the Duisburg Institute for Energy and Environmental Technology, president of the Society for Aerosol Research, and a fan of Rot-Weiß-Oberhausen. Just so you know what is hanging there.
Scenario 1: go for a walk without a mask
Christof Asbach, Aerosolforscher:
“So it becomes risky, or fraught with risk, when they actually stand in front of each other and talk, because then the cloud of aerosol that I expel can be directly inhaled by the other person. If I walk side by side, the likelihood of inhaling this aerosol cloud is considerably lower. “
Scenario 2: full trail with strollers
Christof Asbach, Aerosolforscher:
“To get infected, you need a certain minimum amount of virus that I breathe. It is not known exactly how much, but we are talking about a few hundred to thousands of viruses that you must inhale. And now, if I meet people or overtake them, even if there is an infected person who is spreading viruses, the contact time is very, very short. In other words, it is extremely unlikely that I will inhale so many viruses in this short period of time that it will infect me. “
Scenario 3: jog one after another
Christof Asbach, Aerosolforscher:
“There was a study from the Netherlands last year that said it was critical. However, it has also been criticized relatively harshly because it was investigated under laboratory conditions in the wind tunnel and of course I do not have and cannot have as directed an outside current as I have in such a wind tunnel. So in the real setting, when two runners are running behind each other, this is probably not as critical as it was in the wind tunnel. As an athlete, I naturally breathe deeper and heavier. And of course it also emits a bit more particles and viruses, but it’s still a small fraction of what you breathe out when you speak. By the way, the same applies to the soccer field. I was recently asked if that would be critical. So I say: actually, it only becomes critical when you discuss it with the referee. “
Scenario 4: queue at the ice cream stand
Christof Asbach, Aerosolforscher:
“The moment they talk to each other in such a queue and then they stay there for a long time, it could be critical. So it is certainly advisable to play it safe and also wear a mask. That is also one of the main reasons for the distance requirement that these large droplets require, and then we are talking about droplets, which are then in the range of a few hundred microns, that is, more than a tenth of a millimeter. You can see them directly and they really fly out of your mouth like in a trajectory parabola. And if I get too close, I may be able to inhale them right away. “
Scenario 5: conversation on a park bench
Christof Asbach, Aerosolforscher:
“If you sit there for three-quarters of an hour and talk on a park bench, depending on how big the park bench is, where distance may not be possible, then you should consider putting on a mask.”
Scenario 6: Fully occupied meadow
Christof Asbach, Aerosolforscher:
“Of course, if there are many people there, it increases the probability that more than one is infected. And that means I can have more viruses in the air. At the same time, however, this concentration decreases significantly with the distance from this source to the infected person. If there are more people around the infected person and they do not maintain this minimum distance, then of course the risk for each individual increases. “
Scenario 7: demonstration
Christof Asbach, Aerosolforscher:
»If he speaks, or especially speaks loudly, yells something, sings something, then he emits more aerosol particles and therefore more viruses. And if the minimum distances are not respected, it can actually become a critical event. “
Some cities are currently tightening their outdoor mask requirements, such as Hamburg or Düsseldorf, where it is now forbidden to stand or sit on the banks of the Rhine and in the Old Town at peak times. Does something like that make sense?
Christof Asbach, Aerosolforscher:
“From a purely scientific aerosol point of view, such a general mask requirement is not necessary, but you can proceed in a more differentiated way. But I understand that this may make sense from a political as well as a psychological point of view. Just to remind people that we have a pandemic and that we must protect ourselves accordingly. In those nerve-racking places, where many people just hang out, the likelihood of such situations arising is, of course, much, much higher. So to that extent, you can understand that. And I think a big problem is that in Düsseldorf they just can’t control the situation anymore as to who is now behaving according to the rules and who is not. Critical situations are especially when they are face to face and talk to each other. “
