Radon Measurement (Measurement Professional)
Domain overview
The Radon Measurement (Measurement Professional) domain tests whether you can plan, place, retrieve, and report a radon test that stands up to NRPP and EPA scrutiny. It is less about memorizing device names than about knowing why a test is invalid and what to do before the client asks.
Core rules
- Short-term tests must run at least 48 hours. Closed-building conditions begin 12 hours before the test and continue through it: windows and exterior doors closed, except normal entry/exit.
- Place the device in the lowest livable level, 20 inches above the floor, at least 4 inches from walls, and 3 feet from exterior doors/windows, open foundations, sumps, and HVAC returns.
- Do not test in bathrooms, kitchens, closets, crawl spaces, or hallways.
- Use a calibrated CRM; record hourly readings and document calibration.
- QA/QC: 10% duplicates or side-by-side devices, field blanks, and spikes; keep chain of custody.
Worked example
A client asks for a 24-hour CRM test in a finished basement bedroom. You should refuse the 24-hour schedule: a short-term test must be at least 48 hours. The basement bedroom is acceptable as the lowest livable level if it is regularly occupied, but place the monitor 20 inches above the floor and 3 feet from the sump and exterior door. Start closed-house conditions 12 hours before the test, log the start/stop times, and report the average, not the peak hourly value. If the average is 4 pCi/L or higher, advise a confirmatory test; at 2–4 pCi/L, discuss risk reduction.
Traps
Common misses: treating a 24-hour screening as valid; placing the device in a sump, closet, or near a draft; failing to document closed-house conditions; omitting blank/duplicate results; and reporting a single CRM spike as the result. Another trap is assuming 4 pCi/L is a safe threshold-EPA recommends considering action below 4 pCi/L.