South African Covid-19 News and Discussions 2

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Lupus

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Napalm said:
All these things are merely precautions. How good each one works?? Can be debated.

There is already much to be said between the quality of Masks... (FFP mask is better than Surgical mask for Corona but not as good as N95... and Cloth one's are basically just 2 or 3 layers of normal materials, unless it has some filter in there)

I would agree with Woolies, The shield is good as an "extra precaution" as the shield protects if someone sneezes or coughs directly in your face or maybe next to your face. The mask covers the mouth and nose so you don't breath it in. Or that some droplets don't land close to your mouth and you ingest it somehow.

Having Shield and Mask is obviously much better.

But as Woolies stated. Rules state Mask must be worn (not Shield must be worn)

Having only Shield, you still breathing in fresh air through the mouth and nose, which you can suck straight into the lungs. The shield also don't stop air or droplets coming in from the sides. Most malls have aircons blowing and creating air currents in the air. They will enter from the sides of the shield.
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You know the mask isn't too prevent you from getting it right? It's too prevent you from spreading it
 
Grant

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Napalm said:
Most malls have aircons blowing and creating air currents in the air. They will enter from the sides of the shield.
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I'm surprised some of the malls and bigger shops have not switched to negative pressure ventilation
 
theratman

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Grant said:
I'm surprised some of the malls and bigger shops have not switched to negative pressure ventilation
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I'm sure the cost of conversion is a prohibiting factor, also the property groups must be very short on cash flow. Wonder how hard it would be to convert?
 
Paulsie

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theratman said:
I'm sure the cost of conversion is a prohibiting factor, also the property groups must be very short on cash flow. Wonder how hard it would be to convert?
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Isn't it just a matter of reversing extractor fans and repositioning filters?
 
Gordon_R

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Grant said:
I'm not seeing that statement in any of the links
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The News24 headline states that the W-Cape will reach a peak of new cases before the end of June. This was suggested by the model predictions last month, but there is no empirical or scientific evidence that this will actually happen. Its more a statement of hope than fact.

Given the population demographics, and the lifting of restrictions on 1 June the peak may be delayed. Or cases may continue to rise for several weeks. We really don't know, and neither models nor international experience provide much guidance.
 
Paulsie

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rietrot said:
You'll lose the ability to cool or heat the air.
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Very true, thank you. Positive pressure usually works with 90% recycled and 10% fresh makeup air. As the 90% is generally at or close to required temperature, it just needs to be filtered. With negative pressure, all the new air would have to be supplied and conditioned, albeit at lower volumes than the extracted air.

I guess the best option is to introduce hepa filters, but this will add to cost, put pressure on fans and increase electricity consumption. I don't think there is any incentive for malls to do that.
 
Gordon_R

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Grant said:
I'm surprised some of the malls and bigger shops have not switched to negative pressure ventilation
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There is a difference between what can be achieved on a small scale in an operating theatre with closed doors, and a large scale mall with draughty corridors. Converting entire ventilation systems to purposes for which they were never intended is impractical. Making small changes to specific locations such as restaurants is possible, but will have some cost impact. The benefits are not clear, and there really are not enough technicians to run around doing this randomly at short notice.

Edit: The worst case scenario is an aircraft. Ask them how they do it...
 
Geoff.D

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theratman said:
Honestly wouldn't know, I'm no engineer, was just speculating at costs.
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It is easy to say, but difficult to implement effectively. And no it is is not as easy reversing the airflow.
Even when you try this on a simple device like a desktop PC, you will quickly see what the difficulties are.
 
The_Right_Honourable_Brit

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Gordon_R said:
The News24 headline states that the W-Cape will reach a peak of new cases before the end of June. This was suggested by the model predictions last month, but there is no empirical or scientific evidence that this will actually happen. Its more a statement of hope than fact.

Given the population demographics, and the lifting of restrictions on 1 June the peak may be delayed. Or cases may continue to rise for several weeks. We really don't know, and neither models nor international experience provide much guidance.
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There is preliminary* evidence to suggest WC might have already peaked as the number of cases has decreased for the past 3 days and recoveries > new infections for the past 3 days as well. But yes, too early to tell but the indications are at least in the right direction.
 
Polymathic

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Chris_the_Brit said:
There is preliminary* evidence to suggest WC might have already peaked as the number of cases has decreased for the past 3 days and recoveries > new infections for the past 3 days as well. But yes, too early to tell but the indications are at least in the right direction.
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Western Cape is only testing people that fall into the "at risk" category so their numbers are pretty much useless in gauging the number of cases in that Province.

Gordon_R said:
There is a difference between what can be achieved on a small scale in an operating theatre with closed doors, and a large scale mall with draughty corridors. Converting entire ventilation systems to purposes for which they were never intended is impractical. Making small changes to specific locations such as restaurants is possible, but will have some cost impact. The benefits are not clear, and there really are not enough technicians to run around doing this randomly at short notice.

Edit: The worst case scenario is an aircraft. Ask them how they do it...
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A simple solution since it's winter for many malls is just keep the aircon off and all the doors open, including the emergency exits
 
Paulsie

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