Top 5 Mistakes When Measuring Radon in Mines

With experience from thousands of mining measurements, we've identified these five common mistakes often made while measuring radon in mining environments.

• Using only area radon monitors or detectors instead of personal dosimeters. Radon varies within a mine and area monitors may not reflect individual worker exposure. Workers move around the mine areas, making area monitors in fixed areas unable to report accurate worker cumulative dose. A personal radon dosimeter worn by employees during their workday combined with a coordinated background measurement plan will help satisfy regulatory requirements for worker exposure limits.

• Not measuring thoron (radon-220). Although often overlooked, thoron can contribute to radiation dose in mining environments. Thoron, an isotope of radon, is a radioactive gas with a shorter half-life (55.6 seconds) than radon (3.825 days). Because thoron decays quickly, it doesn’t travel as far and the measurement site needs to be closer to its source. Thoron can interfere with some radon measurements because both gases emit alpha particles. A radon-thoron test kit can provide a breakdown of both gases.

• No ongoing monitoring. One-time testing is not enough. A consistent monitoring plan is critical to detect changes due to ventilation, seasonal variation, or operational shifts. Regulatory agencies such as MSHA and CNSC have requirements for radon measurement and monitoring in mines. Confirm with your national or local regulatory agency for ongoing monitoring and reporting requirements.

• Short monitoring periods. Radon fluctuates hourly, daily, and seasonally. The workflow of mining operations throughout the year can alter the flow of radon gas as well as changes in humidity, outdoor temperature, and barometric pressure. Short-term radon tests may miss peaks caused by such fluctuations.

• Detector placement. Placing detectors near ventilation intakes or too far from work zones skews results. Detectors should be in worker populated locations and at breathing-zone height. Improper placement can lead to an underestimation of worker radon exposure or ineffective mitigation efforts, thereby increasing lung cancer risks.

Accurate radon measurement in mines requires specialized expertise, a personal radon dosimetry plan, and required record keeping. Avoiding these common mistakes ensures compliance with mining safety regulations but also protects the health and lives of miners working underground.