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Comment by gh02t | Hacker News Reader

I recently built a sensor for particulate matter (using the Plantower PMS7003, a laser-based sensor) and it's interesting to look at the effects of every day tasks. Cooking for instance causes a huge spike in PM1.0/2.5/10.0 levels, but so do more mundane tasks like vacuuming or spraying aerosols.

I'd like to add a sensor for CO2, but it's a bit more complicated. A lot of the easy to use sensors marketed for the purpose are MOX sensors and the "equivalent CO2" reading they give is pretty much a complete lie except in a very narrow range of circumstances.

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I have a sensor built into an air purifier and have observed the same. Anything textile-related is bad like shaking out your blanket, which makes carpets seem horrible to me. But frying stuff really is the worst. You can go in the hundreds of micrograms, even with induction.

A positive thing I have also learned is that opening the windows works best to get PM levels to a background level. Luckily it is only in the area of 5-20ug pm2.5 here

For CO2 i have been recommended this one: https://clientmedia.trade-server.net/1768_tfadost/media/8/00... which seems to measure CO2 directly.

Do you recommend the air purifier that you have? And would you mind sharing which one has a built-in sensor? I'd like to try measuring my laundry room.

They are expensive, and it doesn't have a built in sensor, but I have an IQAir healthpro compact and have confirmed with my own particle detector that it filters out > 99% of PM0.1 particles, and 100% of PM2.5 particles.

If you don't care what it looks like, you can easily build your own air purifier for much cheaper. All it is is a blower fan which forces air through 2 or 3 filters, with the last being a HEPA filter. You can get all the requisite pieces for about $100.

We use IQAir machines, too, but buy third party filters from HEPAAirDirect.com as they're cheaper than the originals, and seem very well made. And their pre-filter comes with a removable coarse dust filter.

For the DIY route, these guys in Beijing sell a kit: https://smartairfilters.com/cn/en/

IQAir is just a fan, but it isn't just a HEPA filter. IIRC, the bottom filter is a large particle filter (for dust and hair), the middle filter is a carbon filter (for smoke and paint) and the third is a micro particle filter (<2.5pm). HEPA is a loose industry standard and not everybody meets those requirements anyway.

But yeah, you can easily just put a few dryer sheets on the back of your fan if all you're worried about is large dust and hair particles. The only reason to buy IQAir is if you're paranoid or severely allergic/have health problems.

Most purifiers on the market with built-in sensors are unreliable to measure. They usually go for cheap IR sensors without flow control. Your results will vary wildly depending on conditions (temperature and humidity affect measurements a lot). I personally like Xiaomi purifiers for their affordability and noise level.

If you're concerned about measuring pm2.5 in your space, you should consider buying a good entry level monitor like the laser egg or air visual (acquired by iqair not so long ago).

Don't hesitate to ask more questions, air quality had been my main business for the past 4 years.

We have a Coway AP-1008DH, and it's interesting to see how quickly it comes on when cooking. Probably cheap sensors, but it appears to be a good device overall.

I see that Air Visual ship to Australia; could this be a good way to assess the pollution levels at the school we're considering moving our son to (see my other response in this thread), or could there be cheaper options? Thanks!

We do work with a lot of schools here in SEA. not in Australia yet but AFAIK the market is probably not ready yet.

Are there air quality meters available at affordable prices (say, <= $100) that can easily be integrated with home automation systems? (like, have an api, or that connect to cloud services so that I can capture the traffic?) Also, any recommendations on outdoor sensors? There have been a few crowd sourced efforts over thale last few years, but I've not been very impressed by them.

I don't know of any cheap outdoor sensors, they are more tricky than indoor as wind (air flow in the sensor), temperature, humidity and dust become more of a prominent problem. For a cheap sensor, laser egg publishes API endpoints to get latest data. You can also fairly easily add a plantower to an arduino/raspi kind of setup. Pantower is a sensor that will give you reliable output OOTB, can be improved but good enough.

PM2.5 particulates are also a big problem with woodworking and other manufacturing processes. There, having proper particulate capture (via properly designed hoods, ducting, etc.) and adequate airflow and duct design (to not restrict airflow) is critical.

For kitchen use, the lessons are largely similar: you need a fume hood that's properly designed and installed, with adequate airflow (often rated in CFM in the USA) to hold and exhaust the particulates. The particular heat source used of gas, electric, or induction, doesn't matter so much because it's the heated food, cooking oil, etc. that's throwing off the particulate matter.

The food is part of it, but the heat source must have some involvement. Combustion of gas produces byproducts, no way around it, and studies of camping stoves have shown the cleanliness of burn is wildly variable depending heavily on basic parameters like the shape of your cookware and the distance from the flame.

(For camp stoves, the chief question is carbon monoxide production- if a stove produces low enough levels of carbon monoxide, it's safe-ish to use inside a small tent high on a mountain in a blizzard where you can't cook outside. Climbers have died of CO poisoning cooking in tents, so it is a real possibility)

> ...it's interesting to look at the effects of every day tasks.

I suspect pretty much every task elevates PM levels.

I made a somewhat surprising and definitely unwelcome discovery by turning off the lights in my bathroom, flushing, and shining a green laser pointer around (Rayleigh/Tyndall scattering, etc.). Followed up with the same test while scuffing my feet on carpet and doing a few other everyday activities.

It was interesting, so I'd recommend trying it at home, but not right before dinner. Or breakfast. Or ever, if you have an overly vivid imagination.

I dunno. I'm not really convinced that all particulates are automatically harmful at modest levels, at least not to a degree that is worth worrying about. The stuff that worries me are aerosolized modern pollutants- things like smog, glass dust from cutting fiberglass (particularly nasty stuff), and in the future potentially even new wonder materials like carbon nanotubes.

An air purifier with a HEPA filter and an ionizer will take care of the majority of visible airborne household dust, if it really bothers you.

Are there any schematics / plans for your project? I honestly don't trust Phoenix's sensor data (many times it says things are OK - AQI is green - but just looking around you can tell its not).

I don't have any personally, but the Plantower sensors are pretty straightforward. They just use standard UART serial, you can use an Arduino or even a simple USB-to-serial adapter, the only catch is that it must use 3.3V power and logic. Their datasheet describes how to wire them up and talk to them and you can also find plenty of code examples online.

The PMS7003 is a very accurate laser based sensor with forced airflow, I trust it. Sharp also makes a much cheaper analog sensor based on IR, but I didn't get very reliable measurements from it.

Edit: here you go https://learn.adafruit.com/pm25-air-quality-sensor/overview . Is for the PMS5003 but that's basically the same sensor.

Cooking with gas or electricity?

I've heard before that cooking with gas causes significantly more indoor air quality problems, but I'm curious what your observations are.

My electric stove shoots my AQI through the roof when frying. Made me consider alternate ways to cook.

Though, would like to know if gas is worse, as one alternative I was considering was Donabe, which requires gas.

A fume hood that keeps splatters in and vents a lot would work. I think it's just unavoidable that frying vaporizes/aerosolizes particles, so your options are either vent the contaminated air, or don't fry.

So gas that doesn't fry would be ok? Like, making a stew for example. Am wondering if the gas burning itself produces a lot of particulates.

I don't think a fume hood is an option in my apartment unfortunately.

(You can get a single gas burner to cook things in a donabe)

Gas combusts pretty cleanly and doesn't release much.

I personally wouldn't worry about particulates from cooking that much. Get an air purifier if you want, any decent one should be able to pull that stuff out of the air fairly quickly.

Well, from frying the AQI was sometimes getting as high as 400. That seems...worrisome.

(More typical is 70-150, but that's usually with windows open. Harder in winter)

sorry, i was commenting on the cooking technique (frying) not the heating method. Electric will create less particulate than gas, no matter how efficient the gas. frying will create more particulate than boiling, probably. if you're in Japan (guessing from the donabe reference) you'd probably be better off avoiding restaurants (with their smoking and cooking residue et al) if you're too concerned :)

Actually not in japan. Just looked like a tasty, easy way to make meals and was interested in trying it. Nut unsure of the effects of the gas burner on indoor air pollution.

A quick search suggests this may be a poor idea on air quality grounds: https://ehp.niehs.nih.gov/122-a27/

I think this is what I had originally read that made me curious.

https://www.greenbuildingadvisor.com/article/the-hazards-of-...

This talks less about particulate, it seems. Electric clearly doesn't produce carbon monoxide or nitrogen dioxide.

Cooking with gas doesn't release much particulate matter, but it does release volatile organic compounds. Most of it seems to be from the food itself; if you can smell it then there's stuff in the air. Any cooking involving oil seems to be the worst offender.

Do you have any recommendations for sensors I can buy? I don’t know If I would be able to build one.

Not off the top of my head, but here's a tutorial on how to build one. The Plantower sensors are pretty easy to use.

https://learn.adafruit.com/pm25-air-quality-sensor/overview

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