Follow-up measurement guideline
In colder climates, workplace ventilation may be switched off outside working hours to save energy, causing radon levels to rise. As a result, long-term radon measurements can overestimate the exposure during actual working hours. A more representative annual working-hours average can be estimated by combining a long-term measurement with a short-term weekly follow-up test that compares radon levels during working hours with those over the full measurement period.