Comment by rcoveson
3 years ago
The difference between 0.9005 and 0.90005 is not huge in a medical context, or in a chip fab context, or in any other practical context. We're not talking about the difference between 0.0005 and 0.00005. The numbers in question are 0.9005 and 0.90005, and the point being made is that the 0.9 problem dwarfs the 10x efficiency difference way over in the thousandths place.
That difference is from his comments on the toy model of 1000 cubic feet room and 100 cubic feet per minute recirculating air.
In an operating room or chip fab, the room would be over pressure and the new air coming into the room would be filtered. The cleanliness of that air would be determined by the quality of the filter.
Also, if you need air that clean, you need to have strategies for all sorts of things besides filtering.
The point is, you need to be very careful when you put numbers on the internet, and when you read numbers on the internet. Numbers make things feel more real than they are.
For me to actually trust the numbers here, I would need to see the graphs for multiple runs of each filter.
Yes, but in that case you wouldn't be comparing 0.9005 and 0.90005, but rather 0.0005 and 0.00005. No one is arguing that the difference in filters wouldn't matter in a cleanroom context, just that recirculating air in a home the difference in filtration is more like 0.9005 vs 0.90005, and the difference between those numbers is small (in any context to which they apply).
> In an operating room or chip fab, the room would be over pressure and the new air coming into the room would be filtered.
You're describing a situation where the filter is on the intake, but this thread and article are about purifiers within rooms. I agree that the math is really different in your situation.
Yes, the numbers are from a toy example, one that the author used to make one uncontroversial point in one section of the post. Those are the numbers we are discussing in this subthread, which began with:
> The idea that the difference between 0.9005 and 0.90005 is "small" is … weird.
We aren't talking about a situation where both filters are processing all the air in the room. We're talking about a situation where the filters are only processing 10% of the air in the room. That's the defining characteristic of the hypothetical.
I did a poor job of being explicit in my first reply to etchalon.