Never place it outdoors
This may seem obvious - these are indoor radon detectors. However, some users try to test their detector by placing it outdoors to see if radon levels drop as they would expect. There are two problems with this:
This can lead to condensation buildup inside the device, damaging the radon sensor. Differences in temperature and humidity between indoor and outdoor environments can lead to damaging moisture.
It takes time to see sudden changes in radon level. Because your device reports the shortest-term radon average as a 24-hour average, it takes a full 24 hours to fully appreciate any significant drop in radon level.
Measure in the lowest livable space
You can measure radon in any room where people spend time indoors - after all, the point is to understand how much radon people in the house are being exposed to. That said, the basement or ground floor is where radon enters the home from the ground, making it a good place to start measuring.
Placement position tips
OK, you know where in the home you want to measure. So how do you get the best measurements there? Here are some tips:
Place at approximate breathing height
Place on a solid surface where it cannot easily be tampered with (pushed/moved/damaged)
Avoid moving the monitor during the measurement - especially during the first several weeks
Environmental considerations
For optimal performance, choose a location where:
Humidity stays below 85% humidity
The device can be placed 3ft/1m away from vents, windows and direct sunlight
Temperature stays between 39°F and 104°F or 4°C and 40°C