Radon and changes to safety limits in Canada

Home Inspector with Pillar To Post - Professional Home inspections

Radon is a radioactive gas that exists naturally in the environment in very low concentrations. Radon comes from uranium in the soil. While uranium is not present in significant quantities in most geographical areas, traces of uranium in the soil exist everywhere. As uranium breaks down, it produces radon gas. Radon is classified as a human carcinogen. Breathing radon gas is associated with an increased risk of developing lung cancer. The risk increases with increased concentration of radon in the air and exposure time. The concern is around radon levels that can build up inside a house. Even if you live in an area with fairly low environmental radon, you could still have significant levels in your home.

Radon testing

You can get a relatively inexpensive test to determine the radon levels in your home. Testing strategies fall into two general categories:

short term testing, which may take only a few days; or long term testing, which could take several months. While long term testing gives you a better indication of the radon exposure, people often choose short term testing for faster results.

Understanding Radon Levels

Radon levels are reported in one of three different units of measure:

§  The most common unit of measure in the United States is pico Curies per Liter (pCi/L)

§  The most common unit of measure in Canada is Becquerels per cubic meter (Bq/m3)

§  You may also see the term working levels (WL), common in scientific literature

The following numbers will give you an idea what to expect to see:

§   Average outdoor level is 0.3 pCi/L or 10 Bq/m3 

§   Average indoor level is 1.2 pCi/L or 45 Bq/m3

§  Indoor action level in the United States is 4 pCi/L or 150 Bq/m3

§  Indoor action level in Canada is 5 pCi/L or 200 Bq/m3, ( this has been recently reduced from 800 Bq/m3 )

Action level is the level at which you should take steps to reduce the radon gas entering your home.

Fixing a Radon Problem

If you have radon levels at or above the action level, you should take action. The most common remedial

technique involves depressurizing the soil under your home. If your home has a basement or slab-on-

grade, a suction pipe is inserted through the slab into the gravel below. Then suction is applied to the

pipe to draw radon in the soil towards the pipe, effectively sucking the radon up and out of the home.

The cost for a sub-slab suction system ranges from about $1,000 to $3,000.

In the past, remediation involved a trial-and-error approach. For example, a technician might try sealing

all of the cracks in the basement, such as a gap between the floor slab and the foundation, and then

conduct a re-test. If the re-test shows acceptable levels, you may get away with paying only a few

hundred dollars for the fix. But if sealing the cracks does not solve the problem you will have go to the

next level of remediation. Today, most people feel that it is better to do a proper, comprehensive fix the

first time.

You can also dilute radon by increasing the ventilation rate in your home. Adding a heat-recovery

ventilator brings fresh air into the home, discharges stale air outside, and swaps heat in the process to

prevent heat-energy loss. But this approach does not sit well with everyone since it effectively lets in

radon in order deal with it.

Regardless of the remedial method you choose, getting your home tested is a good first step. Arming

yourself with information about the

various approaches is the next step and

consulting an expert is always a good



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Kevin Welch
American Bulldog Home Inspection Inc. - Rutland, MA

Great info Steve,

Thanks for sharing. How is the housing market in Ontario these days?


Jan 30, 2009 06:24 AM #1
Marg Scheben
RE/MAX four seasons realty limited - Collingwood, ON
Edey - Collingwood, Ontario

Gee Steve, do I need yet another reason to worry?  (For others - Steve happens to be my own home inspector and knows how I panic over every little thing in my home). 

Really, rhis is good information.  Can radon testing be done as part of a home inspection and if so, what would be the additional cost?  Is it an issue in our area at all?

Jan 31, 2009 03:41 AM #2
Joanne O'Donnell
Chic Home Interiors - Oakland, CA

Steve this is really important information and very well written and informative.  I would love your permission to post it on my green site (giving you full credit, of course) and link back to you.  I teach a green build science course in the US and Canada and this is such a great article I'd like to give it more exposure.  Check out my site here.

Joanne O'Donnell, Chic Home Interiors

Jan 31, 2009 10:20 PM #3
Sandi Gerrard
Saint Thomas, ON
It's all about colour

Very interesting.  Are there particular areas in Ontario that might potentially have high levels of radon?

Jan 31, 2009 10:58 PM #4
Steve Lawson
Pillar To Post - Professional Home inspections - Barrie, ON

Hi Kevin,

Thanks for the responce. The housing market is nervous but is still relatively active. I don't think we're going to know how things are going until spring.


Feb 01, 2009 03:31 AM #5
Steve Lawson
Pillar To Post - Professional Home inspections - Barrie, ON

Hi Marg,

The interesting part of the whole issue is that Health Canada doesn't have enough information at this point to know where all the active areas are. Their intention is to eventually have all the homes in Canada tested.

In the US a two day (short term) radon test is often done in conjuction with a home inspection. We do this as well when requested, but Health Canada wants to do longer term testing to show more accurate conditions.

Long term tests are typically 3 months or longer. So I expect we'll  eventually have to deal with the vendor prior to the sale/closing.

Feb 01, 2009 03:40 AM #6
Steve Lawson
Pillar To Post - Professional Home inspections - Barrie, ON

Hi Joanne,

Help yourself. Thanks for the interest.

Feb 01, 2009 03:48 AM #7
Steve Lawson
Pillar To Post - Professional Home inspections - Barrie, ON

Hi Sandi,

At this point Health Canada is testig federal buildings in an effort to help start their own version of the EPA's radon map. So at this time they do not have any definitive information. We have done several short term tests in the Barrie, Caledon and Orillia areas and have results with acceptable levels.

The tricky issue is that site specific soils conditions affect the amount of radon penetration. So if you have one type of soil under your house and get low readings, your neighbour may have slightly different soil composition under their house and get higher readings.

Feb 01, 2009 03:55 AM #8
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