Clarity for your home.Compare radon readings using the same units, averaging period, start date and location. Those details often explain why two displayed numbers differ.
Start with the averaging label
| Display or graph label | What to establish before comparing |
|---|---|
| Latest reading | The underlying averaging period and refresh time |
| Rolling 24-hour average | Whether both values cover the same recent 24 hours |
| Seven-day average | Whether each monitor has collected the full period |
| Cumulative average | The start/reset date and whether the location changed |
| Historical graph point | The selected date, aggregation period and upload freshness |
For example, the Home 2 manual describes several rolling averages and a cumulative value that becomes a rolling one-year average after 365 days. Use matching labels for the comparison. A monitor started yesterday and one running for months have different cumulative records even when placed beside each other today.
Make the comparison repeatable
Airthings' two-monitor comparison guidance asks about matching start times, locations and conditions, and describes uncertainty from sampled radioactive decays. Apply its examples to the models and conditions it names.
Build a comparison record with:
- Exact models, firmware where available, power interruptions and reset dates.
- Units and the full label of each displayed average.
- A common observation time and the last synchronization time for app values.
- Room, position and nearby drafts, windows or ventilation outlets.
- Photos or exports showing the difference over a defined period.
If you relocate or reset a device, preserve its existing record first and follow its instructions for starting a new measurement. Keep each location in a separate record. See placement and offline record-keeping.
Read accuracy figures with their conditions
An advertised percentage may apply only after a defined duration, at a particular concentration, or under specified environmental conditions. Use the stated conditions when interpreting that percentage. The View specifications illustrate conditional manufacturer claims; read the conditions alongside the figure.
When to ask for help
If the difference remains unexplained after checking the periods and setup, send the record to the relevant manufacturers or consult a qualified radon measurement professional. Use that record to help establish the next measurement step.
Follow the applicable EPA response to an elevated test result while investigating the difference. The US testing-duration guide links to EPA's testing and follow-up procedure separately from these comparison checks.
Documentation used
- Airthings — Comparing two radon monitors (September 2021)Manufacturer guidance; named older models, not a universal tolerance · checked 2026-10-12
- Airthings — Corentium Home 2 user manual v1 (June 2025)Manufacturer instructions · checked 2026-10-12
- Airthings — View sensor specifications (April 2026)Manufacturer specifications; sensor methods and conditional accuracy · checked 2026-10-12