Comment by weaksauce
3 years ago
> The idea that the difference between 0.9005 and 0.90005 is "small" is … weird.
it is. that's one minute of filtration and the difference is minuscule. over time, this would trend to zero. in 10 minutes you'd expect to be near the steady state of the room. (obviously not completely steady state since you are filtering some already filtered air and probably introducing more particulates but close enough for an approximation)
It's a 10x difference. It's not small.
In a sealed environment, you're right, you'd eventually end up with all particles filtered.
But homes are not sealed environments.
(0.9005 - 0.90005) / 0.90005 = 0.00049997222
It's a 0.049997% difference, not a 10x difference.
In an unsealed environment, the steady state will be related to amount filtered * % filtered / amount exchanged for any given time period. The difference in % filtered is not a significant factor in the above ratio.
What? Where are you getting the 10x from? Both numbers are about 0.9 and the difference is about 0, not 10. If you are refering to the sticker number, yeah the whole point of that calculation is that a 10x sticker number does absolutely not translate to a 10x difference.
> but homes are not sealed.
Correct, but neither are they ultra high throughput (at which point any filter sitting in the room would be useless anyway, since you never get the filtered air). So "not sealed" is too vague to make any conclusion.
No, a 10x difference would be between 0.9 and 0.09. What was given was about a 1.0005x difference. If you had a child that was .9005 meters tall and one that was .90005 meters tall, you couldn't tell which was taller without a precision ruler.
A E12 filter filters out 99.5% of particles above 0.3 microns.
An H13 filter filters out 99.95% of particles above 0.3 microns.
Assuming a volume of 10000 particles above 0.3 microns:
An E12 filter will leave 50 particles.
An H13 filter will leave 5 particles.
That's a 10x difference.
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in practice the filtration in a room goes down exponentially and quite quickly even with budget filters that only filter out 90%. even in shops where you are sanding.
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