These little gauges are a low cost way to monitor temperature and humidity in your home. Humidity above 55% could cause moisture or mould damage on photos, fabrics and natural materials over a long period of time.
In this photo, the reading on the bottom left is for temperature, and the one on the right is humidity. Forty-five percent humidity is pretty low. You wouldn't want it lower than that. But some rooms in your house may be as high as 80 or 90% humidity.
If you can keep the room where your family valuables are stored at an even temperature and humidity most of the time, that would be ideal. Big fluctuations in temp and humidity throughout the day, can lead to brittleness in things such as paper, fabrics, and plant or animal-based materials.
If you have a woodburner in the livingroom, you might want to store your valuables elsewhere as the extreme daily fluctuations (from cold and damp to hot and dry) may be too much. Creating an environment where the fluctuations aren't too extreme is a good target to shoot for.
Look for these gauges in garden centres or hardware stores.
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