You might conclude that the only real option is to buy a positive pressure fresh air system, but this comparison doesn't match my experience. I have no trouble driving the PM2.5 very close to 0 with a few standalone purifiers in my house (verified with a couple air quality monitors) even during bad wildfire smoke events. I'll grant I live in a modern house which is pretty well sealed, but it's also a question of sizing the purifier to the room's size and drafts.
There are some orthogonal advantages and disadvantages though. On the upside, you'll reduce CO2 and other pollutants from inside your house -- it can get quite stuffy when you can't ventilate due to poor outdoor air quality. A downside is that it may also bring in air at a different temperature or humidity than you'd like (though that can also be controlled to some extent with a HRV/ERV.)
I agree, if you have a modern house you could bring down the levels with air purifiers but having no fresh air exchange really makes the house feeling very stuffy and you could get into very high CO2 levels which have its own set of health impacts.
That 'but' isn't a given, modern houses which are properly sealed should have ventilation as well specifically to address that issue. Proper ventilation comes with inlet filters but those usually don't keep out PM<x> so still the purifier will have to do sme more work because of the constant sucking in of polluted air. However, I honestly do not know how common venitlation is already on other continents than mine where it's been made pretty clear by now that sealing a house equals need for ventilation.
What if the goal isn't to reduce measurable air particles, but remove more mold spore "attempts" from adhering to surfaces in your home? Could positive pressure be superior in that case?
Positive pressure does 'one shot' filtering. All air in the house goes through the HEPA filter once. Hence any spores (or other patrickes) that get filtered, get filtered immediately. Though spores (or particles) that make it through the filter get to linger indefinitely.
It sounds like a good filter and PPS would meet your goal.
Particles that get through the HEPA filter will get pushed out of the house by the positive pressure. Unless your house is literally airtight and you never leave
The best air filters I have found are the IQAir HyperHEPA filters, which are rated to filter ≥ 99% at 0.003 microns, which is smaller than a virus particle. That's why these are commonly used in hospitals.
See: https://www.iqair.com/us/air-purifiers
I went down a rabbit hole when California nearly burned down in 2020 and after lots of research came to the conclusion that buying 7x $100 hepa filters is better than buying 1x $700 filter. So an inexpensive Winix ended up being the best for me. One for each room. More air cycles and much less noise when they're scattered throughout the house. This is just for particulate matter. If one cares about volatile organic compounds, VOC's, they need to invest is several pounds heavy charcoal filters. The thin ones that come on most filters don't do anything other than act as a pre-filter to catch the large particles.
Yeah they are expensive but the best I have found. The 45i is for like 700 square feet for $400. The nice part about Alen purifiers is the filters last just about a year and lifetime warranty
I'm curious about what supplier and system you're using? I'm currently using a bunch of smartair purifier, that gets indoor pm2.5 to close to zero even when it gets really bad outside every year (also in Thailand). But considering installing a positive pressure (ducted) system with HEPA filter due to high co2 levels (tightly sealed house and no ventilation)
I am using Vornado air purifiers, but I don't have air quality monitoring yet and don't care about WiFi features. The higher end Vornados have monitoring built-in, but it is rudimentary and just a light bar. Without air monitors to check them, it's hard to tell, but they seem to work quite well. Vornado excels at producing room-sized torrents that direct air through its filters. We blew out a candle once and the smoke visibly made a beeline towards the Vornado.
I think you've mixed up relative and absolute differences. Both of your examples are in terms of absolute percentage points (pp, sometimes ambiguously labeled %), but relative changes are measured in percent (%). 300% relative difference just means 300/100 = 3x.
> Both of your examples are in terms of absolute percentage points
No, they are both about relative increases. I didn't even write about absolute increases because (unlike relative increases, where the article makes a mistake) absolute increases were the part that the article got right: a rise from 5% to 15% would be an (absolute) increase of 10% … just like the article says.
> 300% relative difference just means 300/100 = 3x
…My point was: 300% relative INCREASE (i.e. positive relative difference) means that it's the DIFFERENCE (increase) between the initial value and the end value that is 300% RELATIVE TO the initial value (thus the end value being 400% of the initial value), not that the end value is 300% of the initial value (which would only be a 200% relative increase).
Let's take, to better illustrate the point, an example with a relative increase below 100%. Let's go with an example with 40% relative increase. So let's say:
* in the reference year, your company made a profit of 5 million dollars out of a revenue of 100 million dollars, i.e. a profit margin of 5%.
* the next year it still made a revenue of 100 million dollars but managed to be more profitable, making a profit of 7 million dollars i.e. a profit margin of 7%.
* The ABSOLUTE increase of the profit margin is (7%-5%)=2%,
* The RELATIVE increase of profit margin is the absolute increase of profit margin divided by its initial reference value i.e. (7%-5%)/5% = 40%.
And my point is: having a 40% relative increase of profit margin means that your end profit margin is 40% higher relative to your initial reference profit margin and is thus (100%+40%)=140% of your initial reference profit margin, not that your end profit margin is 40% of your initial profit margin… which would be a 60% relative DECREASE (i.e. -60% relative increase) of the profit margin.
Not sure if it's quite the same, but Google Fit has a feature that gets your respiratory rate from the selfie camera. They also have one where you put your finger on the camera flash and it uses that to see your bloodflow.
I enjoyed reading some of their results. I see some methodological issues here, however:
1) The test makes you distinguish between real words and a set of words they've made up in some way. As others have pointed out, some of them are pretty obvious non-words. I would expect the results to change depending on the method used to generate non-words.
2) Measuring the performance of a binary classification is a well studied problem with many metrics and approaches to quantifying performance (http://en.m.wikipedia.org/wiki/Binary_classification#Evaluat...). Subtracting the false positive rate from the true positive rate is not among them. The final score is not a consistent estimator of the fraction of words in their corpus you know.
Book seems nice, but its discussion on the German Tank problem sets up code to calculate posteriors from priors that are more detailed than the Bayesian argument in the Wikipedia article. That is useful, but you don't get the problem intuition that the answer is the maximum ID you saw inflated by a factor depending on the expect ID-gap. There are some assumptions in the Wikipedia Bayesian analysis, but they are less determining than the ones in the book.
I think linking accounts to debit cards is pretty valuable on it's own. It opens the door to making payments for a lot of people much easier down the road.
Like how Paypal encourages you to tie your bank account to your Paypal account; they get to charge merchants the credit card interchange rate while taking advantage of the low ACH funding risk on the buyer/purchaser side.
I think they've done something quite clever by (I infer) getting people to join up when they receive money. Venmo puts up an unnecessary wall by requiring that the payee sign up before they can be paid.
... if you want to pay with bank account and allow some small startup to charge it w/o you having any control over it or any way to dispute the charge with your bank
There are some orthogonal advantages and disadvantages though. On the upside, you'll reduce CO2 and other pollutants from inside your house -- it can get quite stuffy when you can't ventilate due to poor outdoor air quality. A downside is that it may also bring in air at a different temperature or humidity than you'd like (though that can also be controlled to some extent with a HRV/ERV.)