Radon in the Air:
Why Dilution may not always be a
Solution
Winnie Cheng, Regional Radiation Specialist
AARST 2014 International Radon Symposium
Charleston, South Carolina
September 30, 2014
Radon in the Air: Outline
• The Canadian Regulations & Guidelines;
Occupational & Environmental Exposure
• Case Study
Rn
• Lessons Learned
2
Occupational Exposure: Regulations
• Nuclear Safety & Control Act (Canadian Nuclear
Safety Commission):
• Nuclear facilities and materials
3
Occupational Exposure: Guidelines
• Canadian Guidelines for the Management of
Naturally Occurring Radioactive Materials
(NORM):




Uranium
Thorium
Potassium
Any of their radioactive decay products, such as radium
and radon)
• Jurisdiction over the use and radiation exposure to NORM
rests with each Canadian province and territory
4
Occupational Exposure: Guidelines
• NORM Industries:
• mineral extraction and processing
• oil and gas production
• metal recycling
• forest products and thermal-electric production
• tunnelling and underground workings
• water treatment facilities
5
Workplace Environmental Exposure
• Canada Labor Code
 General workplaces of federal building
should not be >800 Bq/m3 (21.6 pCi/L)—is
currently under review
6
Canadian Regulations & Guidelines
Occupational Exposure
Ionizing Radiation
Federal Law: Nuclear
Safety & Control Act
• Nuclear mines
Federal Guidelines
• HC NORM Guidelines
(Occupational)
Environmental
(Workplace) Exposure
Radon
Federal Law: Canada
Labour Code (Workplace):
• Radon: 800 Bq/m3 (21.6
pCi/L)
Federal Guidelines
• HC Radon Guideline
(Workplace):
200 Bq/m3 (5.4 pCi/L)
7
Radon in the Air: Non-residential Building
“Radon in the
Air?”
Rn
8
Radon in the Air: Non-residential Building
Features
• Slab on grade
• >1,000 m2
• Numerous
“rooms + open
spaces”
Radon
In some rooms >200 Bq/m3 (>5.4 pCi/L)
With one room >5,000 Bq/m3 (137 pCi/L)
9
Radon in the Air: Mitigation Actions
• Stage 1:
• Sealed pipe penetrations, and cracks on floors and walls
• Set dampers to increase the outdoor air ventilation
• Installed a new HVAC system to improve the overall
ventilation
• Stage 2:
• HVAC adjustments: 24/7
• Stage 3:
• Achieved positive indoor pressure
• Further sealing of perimeter walls
10
Radon in the Air: Considerations
• Dilution is the solution via ventilation does not
apply where
• There are multiple sources of entry
• Radon level is very high
• Key:
• Achieving positive indoor pressure
• Having all occupied rooms tested at once
• Testing enclosed areas that are outside of the
HVAC system may help identify various entry
points and the need of other mitigation actions
11
Risk Management: NORM Program
Canadian Guidelines for the Management of Naturally
Occurring Radioactive Materials (NORM)
Average Annual
Concentration a
NORM Program Classification
800 – 3,000 Bq/m³
Radiation Protection Management
200 - 800 Bq/m³
NORM Management
Background - 200 Bq/m³ Unrestricted
12
Risk Management: NORM
Program
NORM Management
200 - 800 Bq/m³ (5.7-21.6 pCi/L)
1. Introduction of public and incidentally exposed worker
access controls
2. Changes in work practices
3. Reducing the radon concentration levels to below 200
Bq/m³
13
Radon Risk Communication
• Employers should have their workplaces tested in
order to ensure that workers are not exposed to high
levels of radon, and to conform to guidelines set out by
the appropriate jurisdictions.
• In radon prone areas, employees could also be
receiving significant exposure at home.
• Staff who live in radon prone areas are encouraged to
test their homes.
• The need for protection against radon both at home
and at work.
14
Lessons Learned
• “Dilution is the solution” – may not be applicable in
reducing high levels of radon or when there are
multiple entry routes.
• Adjustment of the HVAC system should be considered
along with achieving a positive indoor pressure to
effectively reduce the radon levels.
• Check rooms that are outside of the HVAC system;
may need to consider a separate radon reduction
system such as an Active Sub-slab Depressurization
Unit.
15
Conclusion
• Where applicable, employers should consider the
NORM Guidelines for radon risk management and
protection of workers while mitigation is underway.
• Once remedial work is completed, a long term postremediation measurement must be carried out in the
building to ensure that radon concentrations are below
200 Bq/m3.
• Precautionary principle: To reduce radon below 200
Bq/m3 or to as low as reasonably achievable
(ALARA).
16
17