Can you add an email to your profile, so I can reach out to learn more? I'm really into air quality and been trying to improve conditions in my apartment. You mentioned that

> Generally learn about diffusion in wall construction materials and figure out where organic material is used in your house. If organic material is next to something that limits diffusion (plastic, foam, metal, concrete, cement, paint) it is a possible point of water condensation and mold growth.

which is super interesting — I've found a couple of electrical sockets in my apartment which have a very strange smell, similar to soil/mold (I've confirmed that with other people, just to reduce the chance that I'm crazy). I'm still trying to investigate/fix the issue, and it seems that you know more about that, would love to learn from you.

Thanks for sharing your thoughts, very interesting!

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bflesch 2 days ago | parent [-]

Thanks for your kind words. I've added mail to profile, feel free to reach out.

If you are into air quality monitoring you might like homeassistant either with DIY sensors based on esphome (quite easy if you like very basic tinkering with low voltage) or with some off-the-shelf IOT products. If you just want to have a reliable CO2 sensor I can recommend the aranet4, but unfortunately those are quite expensive.

I had some electrical sockets which were super corroded from the humdity, so that the copper wire turned black even though the plastic wrap of the cable was still on it. The humidity must have moved up the cable for ~10cm. The mold damage that I found a year later was at the same wall, but I didn't mentally connect these two things at the time.

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iyn a day ago | parent [-]

Thanks, I'll reach out!

Re AIQ, I've actually built a couple of devices myself (using different sensors, plantower being the most popular one, but I've played with sensiron and others as well) but I've mostly focused on the PM monitoring.

The sockets that have strange "smell" are actually on the (inside) wall that is the building boundary (i.e. not a wall with a neighbour — these sockets don't "smell"). Still, it's a bit shocking to me that this could happen. Do you know how the humidity "got" onto your wall? How were you able to find out? I'm pretty early in my mini "investigation".

	▲	bflesch a day ago \| parent [-]
		Yes, it might've been lost in translation but my socket also was located on the inside of an exterior wall of the building. So one side was room other side was outside. If all your problematic outlets are located like this, then it might be a condensation/insulation problem. Obviously you should rule out a leaking pipe, especially if someone created a slow leak by putting a nail into a wastewater pipe, and also rule out a damage to the outside of the wall where rain could come in. Maybe you can find out if there was a change to the exterior walls after the house was originally built, for example someone insulating the building by putting foam mats on the exterior walls during the most recent "renovation", or putting insulation wallpaper on the inside of the exterior walls. When houses are originally built, normally experts ensure with calculations that no condensation problems will happen within exterior walls. But after many decades people think they are clever by putting additional insulation on the exterior walls in order to save some money, or to simply change the style of the building. In worst case, additional insulation will move the dew point towards the inside of the wall, and then condensation of warm+humid indoor air will happen within your exterior wall. If it is a wooden building like it's common in the US this can create a mold problem. But it can also be a problem for stone buildings like we have here in Germany, if a wallpaper of wallpaint is used that prevents humidity that is trapped within the stone wall from evaporating. Once you know what materials were used for your exterior wall, you can use a very nice calculator [1] that will show you if the wall has a condensation problem or not. For this you need thickness and material for every single layer of the outside wall. [1] https://www.ubakus.de/en/r-value-calculator/