[mindcrime]

If you do anything that involves having an open flame indoors (and I'm including the flame inside a gas / propane fueled furnace, water-heater, etc., or a gas stove) you should have one or more CO alarms in your home as well. CO2 has its own issues, but CO is a very powerful asphyxiant and can very easily be deadly.

https://www.cpsc.gov/Safety-Education/Safety-Education-Cente...

[benjamir]

I recently bought one of the best CO_2 meters available here (and had a CO alarm since before that): the low temperature boiler (natural gas, 1991) in our kitchen contributes close to nothing to the CO_2 level despite getting its air from inside. Letting it run on automatic a whole workday contributes less than 200ppm in our flat. But an adult and two kids can bring the level from below 500ppm to above 1000ppm in around one hour -- additionally: doesn't really matter if the doors to other rooms are open or not. Ppm fluctuation is (way) less than 100ppm between rooms.

(All time low 380ppm -- 10% above the world average during my birth :-( , highest 1620ppm)

[mindcrime]

Yeah, under ordinary circumstances your boiler or whatever should not contribute enough CO to cause problems. It's when something weird happens that you have to worry (usually). Like if the jet is clogged or something else happens that can cause incomplete combustion. Incomplete combustion is your enemy when it comes to CO[1].

[1]: https://www.abe.iastate.edu/extension-and-outreach/carbon-mo...

[benjamir]

* I wrote about CO2.

* The boiler's flame is visible (through a slit).

* The system doesn't have a separate supply stream -- it takes oxygen from the flat.

An CO sensor seems obligatory to me: after the chemney sweeper (obligatory in Germany) measured 10,000ppm CO in the exhaust stream (defect, not normal operation), I didn't want to depend on a 25y+ boiler's electronics alone.

CO kills relatively fast. Even if rare, I don't want to die caused by a rare event that could have been avoided by spending ~50€ (here)

[treeman79]

Get one that shows actual value.

We had one a new one that just beeps when high. Except it didn’t. Delayed medical treatment for months since it never went off.

Gas company guy showed us how high levels in house was and the alarm was silent. Even with fresh batteries.

[JonChesterfield]

Example? Surprisingly difficult thing to search for and seems an unwise thing to pick off amazon.

[treeman79]

Well kiddie brand is the one that failed to go off. So not them.

[mkeespiet]

Can come CO from candles as well? We do not have any flames inside as we cook with induction, we only use candles as indoor flames. Nice fact: Here in the Netherlands a fire alarm will be obligated starting from this summer

[mindcrime]

Yes, any combustion will produce CO as a byproduct. Candles, fireplace, kerosene heater, the aforementioned water-heater, furnace, etc. And Carbon Monoxide is particularly deadly because it's a "chemical asphyxiant" meaning it binds more readily with the hemoglobin in your blood than Oxygen does.