I bought a couple reasonably priced HEPA purifiers and I change the filters on schedule. Replacement HEPA filters are very cheap.
Also watch out for things that we do indoors that can generate bad air quality. I had a friend who bought a VOC meter and noticed very high readings in his kid's room. He traced the source to his chemical and paint cabinet nearby, which he never considered because he couldn't smell anything. Throwing out a lot of the old containers dropped the measurements to the unmeasurable range.
You can safely put a washer and dryer on the upper floor of a house if you add a proper floor drain, but you’re unlikely to see anyone add a floor drain in new construction because buyers aren’t looking for it. Now multiply that by everything a buyer isn’t looking for and you’re talking real money.
European here, we've always been placing washer/dryer stacks in our bathrooms without needing floor drains. We have machines with a system called Aquastop [1] that stop the water flow if the machine detects a leak inside the system.
Therefore the washing machine is usually in the bathroom, and the shower drain serves both purposes.
They have improved over time, but you need to have a drain for the washing machine anyway so the cost is quite low vs the rather extreme damage a leak can cause.
The real activated carbon filters have 10s of pounds of carbon. The little black foam thing that comes with those 2-in-1 carbon filters is useless.
> Those 2-in-1 filters do exist but cost more. And many are scams because they don't have enough volume of activated carbon.
Any filter with a little bit of carbon added is going to be useless after a few days, or maybe even hours.
The only VOC filters that work have multiple pounds of carbon, with the good filters having upwards of 10-20 pounds. It also has to be replaced regularly.
DHH is also a fan (pun not intended?): https://world.hey.com/dhh/air-purifiers-are-a-simple-answer-...
If you pair if with an Apollo AIR-1 you can have home assistant ramp up and down the fans with a PC fan controller based on live readings of PM2.5 in your home. I did this with the help of Claude code.
https://www.thingiverse.com/thing:6826527
https://makerworld.com/en/models/2470181-nukit-tempest-euro-...
However they look somewhat commercial and I'm not sure the funding/incentives so definitely corroborate with other sources.
Having said that, there are reviews of some DIY models reviewing CADR[1], and it's bizarre to complain about testing decibles since Arctic P14 fans, the most commonly recommended fans, are a thouroughly tested product. Running them at around 25% based on lower PM2.5 readings is almost inaudible from experience.
Though, looking it up it seems that prices for the Winix Zero (including one set of filters) have doubled since I last bought one.
The more effective the filter the more it restricts airflow. If a filter is only 99% effective instead of 99.99% but allows double the airflow, it provides nearly double the CADR. To benefit from HEPA you need a clean side and dirty side, like in a clean-room setup.
I used to work in the cleanest room in the state, that wasn’t a lab, back when I lived in Adelaide, and top-inlet button-outlet in a raised floor data centre is how the air handling units in the main data hall worked, so you can simulate that to a certain extent.
> The more effective the filter the more it restricts airflow.
This isn’t the whole story. Surface area and flow rate are factors.
A residential home is aiming to improve air quality, rather than grow flawless silicon ingots etc.
But a HEPA filter is better than no filter. Even if would be more effective with another.
(Also depends on size of hepa filter and room to clean. Large enough filter and small enough space and Hepa can clean all the air)
If you get to recycle the air through the filter several times, MERV-13 offers much better performance tradeoffs for a residential air purifier because you can recycle the air through it much faster at acceptable noise levels. My home air purifier recycles the volume of my home every 15 minutes or so, vs HEPA filters which produce totally clean air, but since it just mixes with the dirty air that doesn’t matter as much as the rate at which it cleans air.
This level of filter goes in the central air system.
The HEPA purifiers are for scrubbing the finer particles.
Air purifiers are designed to run 24/7 and all they do is catch particles. Eventually all the particles will be caught. The one I got also detects if there is a lot of particles and will spin faster accordingly.
Air filters don't work like sieves. The smallest particles are easier to block than the mid-sized particles. See:
https://en.wikipedia.org/wiki/Mechanical_filter_(respirator)
Clean Air Delivery Rate is often specified for specific pollutants. One is smoke, which is mostly small particles.
According to hepacart [1] 99% HEPA filters do not even exist, since HEPA seems to be clearly defined:
> HEPA filter definition, which requires a filtration efficiency of 99.97% for particles as small as 0.3 microns. "HEPA-type" filters may capture larger particles but are not effective against the finer particulates that true HEPA filters excel at removing.
[1] https://www.hepacart.com/blog/dont-be-fooled-by-hepa-filter-...
What matters is the gradual removal of particles from the air.
The HEPA purifiers I have move enough air that everything gets scrubbed. It works.
My house has a separate central air system with a non-HEPA air filter with a decent MERV rating for the bulk filtering. The HEPA air purifiers do the scrubbing of finer particles.
Don’t overthink this. This looks like knowing just enough to be dangerous but missing the big picture.
You have an air purifier in your kid's room. If this is a fairly large apartment or a house, and you have central air running, how much purer is the air in that room? If your central air system is modern and continuously circulates air throughout the house at a low fan speed, you're effectively trying to purify your whole house with that low-output room-sized HEPA filter. Have you done measurements to see if it does anything?
There are ton of variables here. One is where the return air intake is. My house only has a single return air vent in the hallway on a 10' ceiling (the furnace is directly above that in the attic). I think this is not-uncommon in the western US.
I have a room-sized purifier in each room on the floor, and they accumulate considerable dust. What I don't know is how much of that would have been successfully pulled out into the hallway, if I didn't have the vacuum of the purifier.
This is impossible for me to A/B test meaningfully given all the environmental variables - wind (house isn't airtight, wind pushes into leaks harder), wind direction (wind from the desert brings sand and other small particles), humidity, etc.
If anyone has reading material on properly controlled experiments in this regard it'd be really interesting to see. I honestly don't know if they're more effective than disabling them and allowing the central HVAC a chance to pick it up sans airflow-tug-of-war. My hunch is it's not worse, though I have no expertise here.
Long-winded post but I'll close with an anecdote: when we had those wildfires in the Bay Area back during covid, they were absolutely more effective at getting the soot and smell out of all of our rooms than the status quo.
edit: One thing to be aware of if someone is evaluating these, all of the claimed numbers from manufacturers are based on you running the air purifier on the absolute highest speed it offers. Almost no one actually does this in on these consumer grade freestanding ones, especially in bedrooms, because they're quite loud.
In locations with central air handlers, the filter in that handler already serves this purpose. That’s how my house is set up: Central handler has a high throughout MERV filter. Several rooms have additional HEPA purifiers.
The parent comment also has a fallacious argument in assuming that the CADR is too low if a HEPA filter is present, but even the cheap HEPA purifiers I bought have sufficient CADR to cycle the room over and over.
If you’re in a location with no central air handler (only mini splits or no air conditioning at all) and you have a giant space to cover and you have a constant exchange of air from the outside to overwhelm your filtration (must leave windows open, for example) then what the commenter above would apply. You would be better with a higher throughput, lower rated filter.
For everyone else, it’s kind of a misplaced “well actually” take that has just enough information to feel truthy but misses the bigger facts.
If you put a standard sized air purifier with a HEPA filter in it into a room it will absolutely lower the dirty air of the room. Because over time you're lowering the particle count.
If I turn my air purifier on in my room even with the door open the air quality sensors improve their readings quite dramatically.
I drive the car, you buy the purifier.
You don’t think the parent commenter is also using transportation?
The pollution from transport also occurs with trains, buses, and any other vehicle that has wheels, brakes, or moves fast enough to stir up the air and kick particulates into the air.
People do what they can and control what’s within their reach.
And yes other means of transport also does pollute, but amount is is critical here. You need much less public transport than you need individual cars.
I perfectly understand that there is no quick solution (only quick patch with air purifier) so thats why we should not normalise this and remember to complain (after buying air purifier)
Am I bitter about that? Yes. There is nothing wrong with wanting the best for you. There is something dearly wrong with using what's best for you to make life worse for others.
buying a new house will have $40k in reltor fees alone, $2k for movers, plus the, you know, hundreds of thousands for the new house. and what if I like my current house, it's in a busy hip area?
or should I launch a multi-year lobbying campaign in the city and/or state and/or national level to have roads moved?
https://en.wikipedia.org/wiki/Sanatorium
I guess the modern descendants are the health retreat, the rural airbnb, and the day spa that offers oxygen therapy.
Funny part is that locals here are absolutely scared of any sign of draft or direct aircon. All while it's what actually saves their health lol.
I have always been and am still baffled by this. My whole family loses their minds if there is even a slight draft or AC, whether in the house or car. When my brother visits he incessantly closes car vents and windows. Parents constantly nag to put on warm clothes and avoid drafts etc., and when we inevitably get sick a few times a year mostly from school transmitted cold viruses they gloat about it.
Maybe it's a cultural thing from times without good heat/insulation where drafts meant an actual freezing house, which, yes that would actually have an impact on health.
I’ve got a sensor that can detect no2 and it noticeably spikes when using gas. Switched to induction after that.
Does the area immediately above where the gas stove was have an exhaust fan that vents to atmosphere?
I would have assumed a properly specced exhaust fan would capture and remove combustion products from a gas stove?
I suspect a sufficient ventilation would require something more like a lab fume hood that can pull a negative pressure on the area around the stove.
And from what I have seen, a good number of exhaust fans are straight up fake and just ventilate back in to the room rather than ducted outside.
Culinary Cargo Cult.
It's massively easier to just not create the no2 by replacing gas with induction, and to vent the smoke outside rather than trying to trap it in a filter. I think the introduction of cheap consumer air quality sensors like from IKEA will start to make this problem a lot more visible to people.
On the other hand, when water turns into steam at standard atmospheric pressure, it expands in volume by about 1,700 times.
Whereas the gas in your stove is already a vapour, mostly methane, turning in to mostly water vapour and carbon dioxide. So the expansion ratio isn’t going to be anywhere near as high as that.
I’d say you’re still right.
Still, I wonder to what extent an exhaust fan does help.
If the exhaust fan can vent x cubic feet per minute and the room is y cubic feet in volume then it takes z minutes to full ventilate the room, etc etc.
You’d sure notice if the air in your kitchen was swooshing around at 671 miles per hour.
Nope.
> It helps that the insides of my lungs are being squeezed outwards by the same force.
So you agree your first statement is incorrect. I’m glad we sorted that out.
Do you have a source for that? Because as far as I can see, asthma isn't _that_ less common in countries where gas stoves are barely used, such as germany. Still has like 60-70% of the asthma cases the US has. There's also a ton of other pollutants the US hasn't yet forbidden, but the EU has, which could also explain a lot of the difference in rates.
Don't get me wrong, it's certainly a good idea to get rid of gas stoves. I just think it's a bit much to declare them the primary cause of asthma.
That makes sense but the unverified claim is that gas stoves are the main contributors to asthma.
'Replacing gas stove can help asthmatics as much as some drugs, US experts find'
https://www.theguardian.com/environment/2026/jul/24/replacin...
It's better now with more EVs and low pollution vehicles and the street should be pedestrianised from October.
Surprise surprise.
Which will tend to be less desirable areas, by definition.
One approach, of course, would be to also make existing houses less expensive/desirable. Notably, wealthy people tend to have the resources to fight efforts to do that.
Despite what many in the UK think about it "being full", this is mostly an illusion from how cramped are the parts in which the houses are allowed to go; the country as a whole is mostly undeveloped.
(There are of course other considerations, with "why did you build on a flood plain?" being one of the failure modes in the UK).
Building on farmland has national security concerns (as countries are slowly realizing), as the country ends up dependent on foreign food imports after awhile. Can't grow food effectively when there is a subdivision there instead eh?
In most high demand areas (which are the ones everyone is complaining about, generally), all the decent land (or even just 'normal' land) is already developed.
Bonus - next time around, even the flood plain land might be 'too expensive' to develop on, and folks will only be able to afford houses at the dump, or in a swamp, or the like. Yay.
I've seen that mentality in other parts of the world. The thing is that agricultural land is often protected because it is good agricultural land. It is literally the reason why the cities were built where they were built, since that land provided for the cities. Unfortunately, good agricultural land also tends to be easy to build on and we have a tendency to ignore features that may make it a poor decision to build on. (Such as the flood plains you mentioned.)
If a bunch of good people acting in good faith produce a result an evil mastermind would want does it matter if they are good? On many levels obviously yes, on some practical levels the system and the incentives still need to change.
Generations of men have been taught that when walking with a woman on a pavement, they should always take the side closer to the road allowing her to keep further away from the traffic.
But Dr Iarla Kilbane-Dawe claimed that Londoners should avoid walking too near the kerb because on busy streets, air pollution can be up to a third higher than on the inside of the pavement.
Vehicles are capped at emissions of 3mg/mile of particulates and 30mg/mile of VOC's. Something like 1-2mg of tire material actually becomes airborne PM10 particles every mile (and only about 10% of that for PM2.5 particles).
So, EV's really do a great job reducing emissions from 35mg/mile to <2mg/mile (PM10) or even <0.1mg/mile for PM2.5. A 95%-99.8% reduction in air pollution near highways would seem absolutely fantastic for me and my children!
https://pmc.ncbi.nlm.nih.gov/articles/PMC11636205/#:~:text=W...
> EV's have 100% reduction of NOx/tailpipe VOCs, 100% reduction in soot/tailpipe particulates, 70% reduction in brake pad dust (due to regenerative braking), in exchange for 25% increase in tire wear.
Needless to say, the brake pads have never been touched and when I saw the left front one at around 110,000 to 120,000 to patch that tire, it looked like it was just installed. The regen braking almost completely eliminated the brake pad or rotor as a wear item.
If the weight on each wheel is greater I’d have assumed the tyre would need to be harder, for the same performance.
I would have assumed that would counter the otherwise additional wear, but I keep hearing EV tyre pollution is higher and yet everyone who owns one has always said they aren’t changing tyres an more than they did on their combustion cars.
And the warranty requires proof of periodic rotation. If the tires are wearing evenly, as is the likely case for a new vehicle, then rotation costs significantly more than the pro-rated rebate.
Or an entire truckload of batteries catches fire.
StasheD is an engineer and firefighter, quite eye opening.
And safer, less-flammable kinds of battery are in development. Less-flammable kinds of gasoline are not.
Or is it comparing with the entire gasoline vehicle fleet?
My mistake.
I'm not buying it and you shouldn't be selling it.
Lithium batteries are pretty safe in practice.
Safe enough to not be allowed in checked baggage on commercial passenger aircraft.
Safe enough to kill e-bike riders, safe enough to kill people at home charging their e-bike / e-scooter / electric car.
Perfectly safe.
No trade offs, just safety.
And yet, people travel with one or often more than one battery devices as a matter of utterly unremarkable routine.
https://archive.ph/VadwU : Tanker Truck Fire Collapses Bay Area Overpass
https://archive.ph/4INYw : I-95 Overpass Collapses in Philadelphia After a Tanker Fire
Lithium ion battery fires less so.
Surly you don’t mean to imply that a sufficiently large lithium ion battery fire couldn’t burn down a bridge?
They are driving liquid fuel tankers that can do that around regularly.
Also consider that as battery tech improves new chemistries lower the risk of fire even more. E.g. sodium batteries are very stable right now and solid state will improve that further. There's no way you can make petrol less flammable.
You're going to have to face facts, battery powered vehicles are safer than petrol powered one.
There is evidence of a lot of ugly diseases caused by this, without even mentioning the constant 40+ dB background noise.
Plus the idea of having everything within a 15 minute walk including access to public transport.
And pollution from bus or tram is much easier to control. Looking at you petrolheads who like to "Rolling coal"
In London now many if not most buses are electric.
Once you build anything of significance, a highway gets built to it anyway.
Living in the country gave me bad hay fever/asthma in the city much less asthma.
Not exactly the same thing.
the only plants that survive these days are the ones that spam a ton of pollen, so it gets selected for aggressively.