Failing a radon test can still mean you're compliant
A scary first number isn't a verdict. Here's why daytime ventilation can legally put you back under the limit.
Suppose your two-month passive test comes back at 600 Bq/m³ - double the limit. Before you start pricing up drilling and suction systems, look at how your ventilation actually runs.
Many commercial buildings throttle ventilation at night and on weekends to save energy. With the air barely moving and the building empty, radon accumulates. A passive detector integrates that whole period - every quiet night and closed Sunday - so it can report a figure well above what workers actually breathe during occupied hours. [6]
The legal route STUK provides
For exactly this situation, STUK lets you add a continuous working-hour measurement of at least one week and combine it with the passive result, using a defined formula, to compute an annual working-hour average. [6] If that working-hour figure is below 300 Bq/m³, the workplace is compliant. [5]
This isn’t a loophole - it’s the regulator’s own method, and every figure is submitted to STUK. In roughly half of failing workplaces with timed ventilation, it shows no remediation is needed. [6] That’s thousands of euros not spent on a fix you don’t actually need - which is exactly why it’s worth measuring before you build.