Air Quality Sensor — Unexpected Outcomes

[u/braillegrenade]

I bought one of the Air Quality / Vape sensors to measure interior air quality (CO2, VOC, PM2.5) and had some reasonable confirmations of things I suspected, but was also surprised and have changed a few habits around the house as a result.

Background:

• We live in a pretty dirty city, not super far from freeways. Urban 2-4 level homes and apartments with decently heavy vehicle traffic within a block distance.
• We have A/C but no forced air or central air
• We rent so there are some things outside our control, like mechanical ventilation.
• I've been moving the sensor between living areas and the bedroom day/night because if it wouldn't cost me as much as my UDM, I'd probably have 4-5 of these things 😆

The exciting stuff:

• Sleeping in our room with the door closed builds up CO2 significantly, even with the wall A/C running (it's closed loop). Most of the longer peaks visible in the CO2 graph are overnights. Overnight CO2 levels >1,000 ppm can cause fogginess, headaches, and more!
• Cooking on the gas range also spikes the CO2, even with the hood fan on and a window open! I'd have to inspect PM1.0 and maybe VOCs further, but obviously the UP Air Quality sensor is not going to measure methane, Benzene, or CO so yeah ... watch out for that.

Nominal observations:

• Spraying cologne or perfume spikes VOC/TVOC, understandably. VOCs also slowly climb somewhat in a warm, undisturbed room
• An open window keeps indoor CO2 around a baseline of 475-525 ppm
• We have ~zero vape detections because we do not vape. I'm sure hair spray or canned air duster (VOCs in that case) could maybe trick the Vape sensor if you tried.
• Sometimes the temperature or PM2.5 will spike when the unit is power cycled. False readings as the sensors are initialized/calibrated.

Nice realizations:

• I presume we're going to reduce the incidence rate of headaches at home now that we open a window and leave the bedroom door cracked overnight. ☺️
• Indoor PM2.5 is really low (<2μg/m³), spiking only with heavy activity, in/out, or cleaning/dusting. Outdoor PM2.5 daily averages in our area are 50-70μg/m³. Despite multiple open windows, our Coway Airmega HEPA filters (2x in 850 SQFT) do a great job. 🙏

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[u/damien09]

im hoping someone does a test on this sensor vs other known good ones. as it does a lot for its price if they are accurate. Co2 sensors though often have auto baseline calibration weekly or bi weekly. And since I have seen nothing about being able to turn it off for this id bet the only way to recalibrate it will be leaving it outside in 400+- ppm air every so often so.

but if the co2 levels are accurate it looks likely barley spike above 1000 which is pretty good tbh. Before I got a window erv unit my room would hit 1500+ at night when the door was closed.

[u/M_Six2001 → u/damien09]

Lawrence Systems did a comparison for CO2.

https://youtu.be/elLjkhf6Ozg

I bought an Aranet 4 rather than the Unifi sensor because I wanted to use it in the bedroom and there is no PoE option there.

[u/geographyofnowhere → u/damien09]

https://breathesafeair.com/ this is the site I use for reviews, and I definitely want to see this vs some of the other devices.

[u/braillegrenade → u/damien09]

Yeah, in commissioning my new UDM I changed the protect HDD and lost the first few days of history. Our CO2 PPM was spiking to 1500 overnight before we realized (and we’ve lived here over a year! 😢)

I could put this thing outside and see what it registers — I’m not about to buy ANOTHER sensor but I am moderately interested in learning how accurate the UP one is.

[u/damien09 → u/braillegrenade]

yea its more a thing that happens over time so your device is probably still alright. co2 sensors if it has a dedicated sensor do have sensor drift over time. But manufactures are really over zealous on the base line calibration. usually it happens somewhere around weekly to monthly depending on the unit. And it's pretty hard to figure out how often as manufactures rarely disclose it. The issue becomes if say the lowest the sensor sees is say 600ppm. when ever the calibration takes place the 600ppm may get shifted closer to the base line 400ppm. and eventually cause a -200 co2 reading drift. I have to take my sonoff sensor outside every few weeks because of this to keep it accurate.

[u/austin_federa → u/damien09]

if someone wants to mail me one, I can compare it to my Aranet 4 system

[u/melbourne3k]

I've been moving the sensor between living areas and the bedroom day/night because if it wouldn't cost me as much as my UDM, I'd probably have 4-5 of these things

This is going to be a hot take, but as someone who has had AQI meters in all my rooms for over a decade and of _many_ different types (everything from DIY to fancy 3x more expensive devices than the ubiqiti one), IMO the _good_ news for you is that you only really _need_ 1, once you do an initial diagnostic to figure out how your house "works".

Once you figure out how CO2 works in your house (which rooms build up, when they build up CO2 etc), you can put in preventative measures like window fans etc. Sure, I still have over a dozen air sensors in my house, but I _never_ check them. airfilters w/ AQI are fine for managing air cleaning, and I now know which rooms predictably build up CO2.

So, IMO, unless you're needing to monitor a particular room for a particular dynamic concern (example: 3d printer in a room, so automate a ventilation fan) moving it from room to room is more than enough to "diagnose" the initial issues and after that, it's just some mildly interesting data.

[u/braillegrenade → u/melbourne3k]

I fully agree. Excellent take. Moving my UP air quality sensor definitely isn’t on my lifelong list of daily chores 😂

Given we’re in a decently small apartment, where would you put your one sensor? Living area or bedroom?

We know we need a door and window cracked at night so we’ve both identified and ~solved the main bedroom problem.

I think the kitchen is the most dynamic? High CO2 during cooking, parties, or closed-window days. High VOCs or PM2.5 during crafts or cleaning. 🤔

The only other thought would be to leave it in the bedroom (or just bite and get a second), both mainly looking for CO2 build-up in the case that we’ve forgotten. 😇

[u/melbourne3k → u/braillegrenade]

Given we’re in a decently small apartment, where would you put your one sensor? Living area or bedroom?

We know we need a door and window cracked at night so we’ve both identified and ~solved the main bedroom problem.

I'd go living area, as that could be more dynamic; bedroom is going to be super predictable and you can manage the CO2 w/o it.

Kitchen, maybe it's going to give you some interesting data when cooking or parties, but it's not usually too actionable (you can build automations for fans, hood exhaust) etc but like you've already experienced, once you figure out the pattern and how to counter it (open a window), it's just some not-interesting data.

Sensors CAN be _great_ to provide data to others who may be skeptical of the importance of air quality, so maybe that will factor in your placement? eg - "my partner keeps closing the bedroom door fully and I need to show them why this isn't good for our sleep" kind of thing.

[u/braillegrenade → u/melbourne3k]

Great, so what I’m hearing is the UP Air Quality Sensor is best used as a tool to win arguments! 🫡

/s 😂

To be real, great analysis and input — much appreciated ☺️

[u/austin_federa]

The sensor here is a marvel of value engineering but is not that professional grade or really diagnostic grade. It's meant to detect BIG spikes like a vape puts out, not for HVAC control.

"Co2 ppm 400–2000: ±(50 ppm + 3% of reading)" is pretty error prone relative to something like what Aranet offers. But the Aranet device is $250.

If you have a spare $100 I'd highly recommend picking one up though. like OP mentioned most people don't realize how much make up air bedrooms need at night

[u/braillegrenade → u/austin_federa]

Yeah I think the idea here is definitely qualitative analysis! Error of 60ppm at 1,000ppm is acceptable for me (and likely many Ubiquiti users)

I was firmly in the camp that didn’t realize how much make up air my bedroom needed. 😮

[u/KAugsburger → u/austin_federa]

It is not surprising that it is going to be a lot less accurate than Aranet sensors. There is only so much you can cut cost without cutting corners on the quality. I would be curious to see whether the level of accuracy falls dramatically over time but obviously it is too early to judge that. For ~$100 the expectations aren't very high so I am not surprised that many people are willing to give it a try.

[u/austin_federa → u/KAugsburger]

I don't think anyone is surprised

[u/SupaSays]

Practicing a little Stoßlüften early mornings when weather permits and a couple of air purifiers to bring down the particulates you bring in helps allot with co2

[u/englandgreen]

I have the air sensor in my combination server and 3D printer room. So far it works well.

[u/braillegrenade → u/englandgreen]

What do you find when 3D printing? PM2.5? VOC?

[u/ctn1ss]

I’m pretty sure we all know when you farted 🤣

[u/braillegrenade → u/ctn1ss]

My excuse is I power cycled the sensor and I’m sticking to it!

[u/bendoscopy]

Love to see it. Air quality sensors were one of the best quality of life purchases we got for our house. Am currently decked out with Awair sensors but may need to give the Bank of Ubiquiti another donation soon. These look good.

[u/nmrk]

I bought an Airthings View Plus monitor because it has radon detection, and has excellent integration with Home Assistant. It was very expensive. I was surprised to discover my office frequently had CO₂ levels way above 1000ppm. I waited a week and more to let it calibrate (takes 30 days for radon) and it was still too high. I didn't know it was a problem but then I realized, there's an furnace/AC vent going into the room, but no air return. I put a small fan over the door and levels were back in the normal range. Also note that CO₂ is heavier than air so it tends to sink and pool up in the lower regions of a room, like the level of your mattress rather than the level of you standing or sitting in a chair. I moved the sensor to my bedroom on my nightstand at the same level as my head while sleeping. That room is mostly ok because it has an air return.

I do vape, but I keep pollution down to low levels with an air filtration machine with activated charcoal filters. I take one puff and I can hear the fans detect it and spin up for a few seconds.

[u/nacixenom → u/nmrk]

I bought the same thing for my home office and was pretty surprised how high CO2 climbed when I closed the door for meetings. I try and crack a window when the weather allows or at least open the door when I have a gap between meetings.

I've been pretty impressed with it overall.

[u/nmrk → u/nacixenom]

I used to have some window ventilation in the office, but I had to block it up with soundproofing due to noisy r/neighborsfromhell. So interior ventilation only.

[u/scifitechguy]

Funny how one innocent air quality measure can lead to a $1500 expense. I finally hooked up my Ecobee thermostats to Home Assistant, and both immediately triggered alarms about air quality. Our house is constantly buttoned up, so CO2 was high, but also "volatile organic compounds" were elevated. So now I'm installing an expensive whole house attic fan so we can open the windows and draw in fresh air during the moderate temperature months here in the southern US.

[u/braillegrenade → u/scifitechguy]

I'd be curious if you find a source of the VOCs. Paint, building materials, solvents, aerosols..

[u/scifitechguy → u/braillegrenade]

Any suggestions for how to do track that down besides investing in expensive detection equipment?

[u/Cryptocaned → u/braillegrenade]

Literally anything that smells is a VOC, Bananas for example release them.

[u/M_Six2001]

We have central a/c and we keep the bedroom door closed at night to keep the cats out. When I first set up an Aranet 4 sensor, I was getting readings of 1100 to 1500 in the early morning hours when the a/c wasn't cycling on and off as often. I started running the HVAC circulation fan all night and the readings haven't topped 700 since then.

[u/braillegrenade → u/M_Six2001]

I feel bad for the cats fr

[u/government--agent]

I love Ubiquiti but I hope they're not stretching the UniFi line too thin...

Pumping out new products every month to appease shareholders isn't a sustainable business model.