I discovered a tool that is very useful for me, called Mold Alert, by the same folks that make Kill-a-Watt.
Download Manual...
The unit has a digital thermometer and a digital hygrometer and a built algorithm that calculates when mold growing conditions are present.
When those conditions are present, a red light blinks and there is an optional alarm that will beep.
The unit does not detect mold, rather the conditions for mold growth.
Here where I live in the Pacific Northwest, mold is a big issue, and having a device like this is very useful.
I did discover that my basement is pretty much a perpetual mold garden... so some serious work really needs to be done down there.
The parts of the house that I don't heat are borderline, with mold growth conditions being met from time to time. The heated portion of the house is always safe.
I've learned a lot from this thing already, and I am interested how things look as we go deeper into winter.
Available from Amazon for $27.99
or...
Available from Amazon for $21.99
-AC_Hacker