You have an elevated result
Ask the laboratory to explain the report and whether action is recommended. Give the specialist the actual result, units and duration of measurement. A screenshot of one peak on a monitor is less informative than a complete report.
The property is more complex
Basements, several floor types or additions built at different times can complicate mitigation. A specialist assessment helps identify whether one system can treat the relevant ground-contact spaces or whether a combined approach is needed.
An existing system needs attention
If a fan stops, noise changes, or a later test remains elevated, contact the installer or an experienced radon contractor. Ask how to check operation and who is responsible for maintenance. Do not assume an installed system continues working indefinitely without attention.
Questions to ask before instructing work
Ask for experience with similar buildings, insurance details, a written scope, the proposed discharge location, running costs and a plan for follow-up measurement. Establish what happens if the initial installation does not achieve the intended reduction.
Sources & further reading
UKHSA: Action Level and Target Level ↗UKHSA: reducing radon levels and historical costs ↗General guidance for property owners. Check the original source and obtain advice specific to your building.