Most countries and states have laws or guidelines for how long you must measure during a home inspection.
In the United States and Canada, you have to measure a minimum of 48 hours.
We recommend measuring at least 48 hours with the Pro.
Keep in mind that radon levels change and you want to get a good average reading. For the optimal radon level reading, we recommend measuring for 1 month or more. Generally speaking, the longer you measure, the more accurate your readings will be.
We also know that some radon mitigators that give a Home or Wave to their customers as a gift should they have higher levels. This allows homeowners to measure the radon level continuously as radon levels change with the weather and seasons.
A one-time, spot measurement of the radon level is not a good indicator of the radon exposure throughout the year. However, it is much better to do one 48-hour measurement than to never measure at all. In addition, enforced 48-hour measurements improves the public's awareness of radon.