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Comment by com2kid | Hacker News Reader

My cheap co2 sensor shows dramatically different readings for my office with the window closed vs open. It is great at reminding me to crack my window open to get more air flow.

Its temperature sensor is within a couple degrees of my nest's remote sensor.

My Amazon vo2 sensor can tell if I turned my kitchen fan on to a sufficient level to clear out whatever I am cooking.

Lots of sensors don't need to be precise, they just need to indicate if some action needs to be taken.

e.g. If there is a fire, I just need the alarm to go off, I don't care how hot the fire is.

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Exactly, the co2 sensor in my home office really only needs a few levels:

Windows have been open with fans running for a while (~430)

Windows have been closed for a short time (~700)

Windows have been closed for a long time (~1200)

Windows have been closed and someone has been cooking downstairs on the unvented gas stove (~4000)

I have an $80 monitor and it doesn’t seem trustworthy. It has very similar low values 90% of the time, barely ever correlated with forecast AQI I get online. And even when it was wildfire season and I walked out in the smoke (150 AQI) with it the values only bounced around a bit but still were <50 AQI 80% of the time and still <100 AQI the remaining time.

I rather like the environment devices for Raspberry Pi. Surely they aren't "professional level," but for things like CO2 and other particles and gases, you can generate scrolling graphs. That lets you always know whether things are going up or down at any given moment.

Most of the store-bought devices just beep if too high etc, but having a visible graph certainly tells you if it is measuring anything at all, and if you need to crack open a window or blow out the novel candle you just bought from the dollar store.

> My cheap co2 sensor [...]

Which one?

Agreed, as long as deltas are consistent I find the devices useful. I feel like fitness tracker step counts fall into the same category--I don't care much about the absolute number is, but rather how that changes over time and correlates with other behaviors.

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