Radon levels vary over time, even during the course of a single day. The goal of radon testing is to determine the annual average level of radon. This can be done with a single long-term test or with a series of short-term tests.
Professionals test radon levels using a continuous radon monitor. This is an electronic meter that takes hourly measurements of the radon levels over a 48-hour period. These readings are then averaged to obtain the final test result.
Homeowners can purchase short-term test kits from their local home improvement store. These kits are placed on the lowest level of the house for a several days and then sent to a lab for analysis. If you do your own testing, it is very important to read and follow all directions to get an accurate result. For best results, you should use two test kits at the same time and average the results.
Long-term test kits can also be ordered from various sources such as the National Safety Council.