Radon Level Calculator (pCi/L ↔ Bq/m³, Risk & Mitigation Sizing)

How it works

1 pCi/L = 37 Bq/m³ · annual estimate ≈ short-term × 0.8 (winter, closed) / × 1.35 (summer, open) / × 1.0 (closed, mild) · EPA action level 4 pCi/L (148 Bq/m³); WHO reference 100 Bq/m³ (2.7 pCi/L) · risk interpolated from the EPA "Citizen's Guide" table (per 1,000, lifetime) · sub-slab fan ≈ 60 CFM ≤ 1,500 ft², 90 CFM ≤ 2,500, 150 CFM above

Radon is a radioactive gas seeping from soil into buildings, measured in picocuries per litre in the US and becquerels per cubic metre elsewhere, and it is the second-leading cause of lung cancer — with the risk roughly proportional to the long-run concentration and multiplied several-fold in smokers. A single short test is a snapshot that swings with season and ventilation, so results near the action level are confirmed before spending on mitigation, but the fix itself is well established: a fan drawing air from beneath the slab or a crawl-space membrane and venting it above the roof, which reduces most homes to near-outdoor levels.

Worked example

A winter short-term test of 6.2 pCi/L (229 Bq/m³) suggests an annual average around 5.0 pCi/L — above the 4 pCi/L action level and well above the WHO reference. For never-smokers that is roughly 9 lifetime lung-cancer deaths per 1,000 people (about 76 per 1,000 for smokers); a second test to confirm, then a single-point sub-slab system with a 60 CFM fan for a 1,400 ft² footprint, typically $1,000–2,500 installed and about $80 a year to run, should bring it under 2.

Frequently asked questions