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Comment by dolni | Hacker News Reader

I see a lot of people who talk about CO2, and I hear almost nobody talk about CO.

CO2 is much easier for our bodies to deal with than CO. CO2 won't kill you unless it's at exceptionally high concentrations. In cold regions, gas burning furnaces produce a good deal of CO.

There are alarms for CO, of course. But in the course of researching CO & UL standards around alerting, I found that most consumer CO alarms don't even alert until CO is above 30ppm. Additionally, for UL-certified CO alarms with an ambient "max reading" function, they don't even report anything below 10ppm.

Levels as low as 5.5ppm have been shown to significantly increase risk for low birth weight: https://pubmed.ncbi.nlm.nih.gov/9872713/

For context, the CO level outside, where there is fresh air, is 0-2ppm.

Carbon monoxide really is the silent killer and doesn't get talked about enough.

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I agree. But in most homes/office spaces, there is no source for CO, so people don't worry about it too much. It's of course a different matter if people have to heat their house with coal firing or something similar. Every winter I heard stories about CO deaths in developing countries again. That's really sad :'(

Additionally, in many states there is a requirement to have CO detectors anyway, and it is generally built-in functionality to modern smoke alarms. So it's a double whammy of many homes not having any source of CO plus having built in detectors.

I think you've sort of missed the point I was making. Yes, CO detectors will alarm when CO levels are high enough to kill you.

They will intentionally NOT alarm if there is a low, persistent level of CO that probably has devastating health effects over the long term (think 20ppm in your house all the time).

Some years ago, my furnace had a cracked heat exchanger and, unknown to me, was pushing CO into my living space. I only noticed by luck. I walked by one of my CO alarms, hit the "max level" button and thought to myself that 25ppm is quite high. So I reset it and checked it again the next day. Sure enough, it shot back up.

You don't need to fire coal to produce CO. Both natural gas and propane produce CO when combusted. In a home, a small crack in your furnace's heat exchanger is all it takes.

It's very common for natural gas to be used to heat homes and office spaces, at least in the US.

Additionally, water heaters and dryers might use natural gas. Gas stoves do, too.

You ever notice how CO alarm instructions have a blurb about not putting the alarm too close to your furnace, or too close to a gas stove?

Cooking on a gas stove?

Every home has a CO sensor, at least where I live. It's required. What gives you the feeling that people are ignoring it? People are very aware of it.

CO is something everyone is aware of - growing awareness that less lethal things are also important is what's driving CO2 checking.

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