There are several commercial ways of measuring the level of radon gas in your home.
The most common and cheapest tool is a short-term passive radon detector, which can be purchased from most hardware stores or ordered online. It costs from $10-$30 and is easy and quick to operate, but must be sent to a lab for analysis.
For a more accurate reading there are long-term detectors, which must stay in your home for up to 90 days.
The ideal location for placing a passive radon detector is several feet away from any windows or doors and at breathing height. In most cases, this is difficult, so placing the detector 10cm above the ground is sufficient.
A company can also be hired to come to a home and measure the concentration of radon. However, this is more expensive than a “do-it-yourself” radon detection kit.