The importance of yearly radon testing in underground mines

Tuesday, April 11, 2023

Understanding the legal requirements for Ontario mining operations

Radon Assessment Information Sheet

Cover of radon assessment information sheet

Under the Occupational Health and Safety Act (Act), employers are required to take every precaution reasonable in the circumstances to protect workers from hazards in the workplace, including exposure to hazardous substances such as radon. The Act also requires employers to conduct workplace assessments to identify hazards, and to implement appropriate control measures to eliminate or reduce the risk of exposure to hazards, including radon.

Radon is a naturally occurring radioactive gas that is released from the decay of uranium in soil and rock, and it can accumulate in enclosed spaces such as mines. Radon is known to be a potential health hazard, as prolonged exposure to elevated levels of radon can increase the risk of lung cancer. So, it is especially important for employers in the mining industry to assess and manage radon risks in the workplace to ensure the health and safety of workers.

“Mine operators in Ontario need to stay updated with the latest regulations, guidelines, and best practices related to radon testing and management,” says Keith Birnie, Industrial Hygiene and Ventilation Specialist at Workplace Safety North (WSN).

“Expert radon assessments are available from WSN specialists who will help ensure compliance with all applicable laws to protect the health and safety of workers. Mining operations can also get help to develop and implement an effective radon testing program.”

“Section 289 of Regulation 854 Mines and Mining Plants says that underground mine air has to be assessed for radon before work begins in a reopened mine, and within six months of the opening of a new mine," notes Birnie.

Air in an underground mine must be assessed at a minimum:

  • Monthly, if the radon progeny concentration in a sample exceeds 0.1 working level; and
  • Quarterly, if the radon progeny concentration in a sample is greater than 0.06 working level up to and including 0.1.
  • If the concentration of radon progeny in a sample is less than or equal to 0.06 WL, once a year a competent person will assess whether to retest the air in the work area in the underground mine and will also consider previous test results and any changes in the mine or its operations.    

Samples are taken in areas where the highest radon concentrations are expected and where worker exposure may be an issue. Such locations could include:

  • Sumps (radon gas can be carried into the mine with the water)
  • Unventilated areas (to detect if gas is emanating from the host rock)
  • Active headings and old workings being re-opened
  • Exhaust airway (to determine if any gas is being produced in areas not otherwise assessed)
  • Other locations that may be determined while on site

Radon gas moves through cracks in rock and dissolves in water or natural gas. It enters a mine with water, gas flows or seepage. Sampling will take place at areas where the highest concentrations of radon progeny could be expected and where worker exposure may be an issue.

For more information, contact Keith Birnie, WSN Industrial Hygiene and Ventilation Specialist.


Assessment services

Occupational disease prevention resource material includes Mining Workplace Environment Checklist, Industrial Hygiene Basics: Setting up and Implementing an Effective IH Program, Radon Management through the Life Cycle of an Underground Mine, and more