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Radon in Michigan:
What Every Home Buyer Needs to Know

(please note that while this article is written primarily with Michigan homeowners in mind, there is much to be learned by homeowners in any of the states served by GLC-ASHI)

  1. Radon is an invisible, odorless, radioactive gas that comes from natural uranium in the soil.
  2. Some areas have more radon problems than others, but homes with radon problems have been found in all Michigan counties.
  3. Radon is acknowledged by major health authorities worldwide to be the second leading cause of lung cancer.
  4. Approximately 12% of homes in Michigan have dangerously elevated levels of radon.
  5. All radon problems are correctable. In most homes, radon levels can be reduced for around $800-1,200
  6. No one can tell which homes have radon problems without testing. Age, foundation type, weather-tightness or neighborhood trends are not useful indicators of radon levels.
  7. Only active monitors with environmental sensors should be used for testing in real estate transactions. Passive tests can be defeated by tampering, and the buyer would have no way of knowing.

Testing for radon:

Radon is invisible, odorless and chemically inert. No meaningful test can be done instantly. Since radon levels in a building vary hourly and seasonally, the ideal tests are those which sample the building’s air over a period of many months. Since this is often not practical, short-term testing methods have been devised. A short-term screening test requires a 48-hour minimum testing period, and closed house conditions. There are 2 methods of testing:

A passive test usually consists of a can or bag of activated charcoal, or an electret device in a small container. These tests produce a single reading for the entire length of the test. They must be sent to a laboratory to obtain the result. Including mailing time this can take from 2 to 14 days. Passive devices are suitable when homeowners are testing their own house. They have virtually no means of detecting tampering, and therefore are inappropriate for real estate transactions. Most passive devices must be used in pairs (with their results averaged to produce an accurate reading). A few hardware stores and home centers carry these tests, and some County Health Departments distribute them at cost for non-commercial users.

An active test uses an electronic monitor that produces a radon reading for each hour of the test period. The best monitors also track room temperature, humidity, barometric pressure and instrument movement, and report this information for each hour. Any attempt to tamper with the test conditions, such as opening windows or moving the monitor, will show up dramatically on the printed read-out. Fully-qualified service providers can download the readings directly from the device at the end of the test period, eliminating the extra waiting period. The more sophisticated active monitors are ideal for testing in real estate transactions. A good active monitor costs about $4,000. If you need accurate, quick and reliable testing, you should call a service provider with this type of equipment.

Just what are ” Closed House Conditions “? It’s quite simple: All windows closed. Exterior doors closed except for normal entry and exit. Air exhaust routes closed. (hood fan off, fireplace damper closed, bathroom fan off) For an accurate short-term radon test, these conditions must be met for the whole test period, and for the 12 hours before the start of the test period. Some types of testing devices can be damaged by dust or organic vapors, so painting, floor sanding, and other such activities should be suspended for the closed-house period. Closed House Conditions do not prevent living in the house or showing the house.

What about tampering? When a home is being sold, purchasers often ask for a radon test to help them make an informed decision. Because the seller is usually in control of the house at that time, there is a possibility of test tampering. This could produce a test result that does not reflect the actual radon level in the home. A good testing contractor will have the seller or their agent sign an agreement to maintain closed house conditions. The use of sophisticated active monitoring equipment is the best protection against tampering.

What do the test results mean? Radon is measured in picoCuries of radon per liter of air, expressed as pCi/l. Outdoor background radon is usually around 0.3 pCi/l. A typical basement reading is around 1.5 pCi/l. The action level, determined by the US EPA, is 4.0 pCi/l. Any level at 4 or higher should be reduced, and you should consider reducing levels between 2 and 4. The actual cancer risk from radon exposure varies with the radon concentration, the number of hours you spend exposed to that concentration each day, and how many years of your life you are exposed. Good risk comparison charts can be obtained from Sherlock Homes Inspection, Ltd., email request to The important thing to keep in mind is that 4 pCi/l is not a “magic” safe level. The 4.0 action level was chosen because at that time, levels lower than that could not be reliably reduced. The mitigation methods available at that time were only reliable at levels above 4. These decisions were made during the early days of radon research (mid 1980’s), and a great deal has been learned about the science since then. Good radon reduction systems now routinely achieve radon levels in homes below 1 pCi/l, with less noise and energy cost than the earlier systems. Keep in mind that there is a substantial annual cycle in radon levels. If your test was done in the summer, and the result came back at 3.1, for example, you can be fairly sure that it will be over 4 in winter. Also remember that your home may not be your only exposure point for radon. Has your workplace or school been tested?

Fixing a radon problem.

One might think that removing a colorless, odorless, chemically inert gas from the air of a building would be very difficult, but the principles are surprisingly simple. To remove radon, one must first understand how it gets in. (For purposes of clarity, this discussion centers around mitigating radon in a basement. Slab or crawlspace mitigation works on similar principles.)

Few of us are accustomed to thinking of the air in a home as a finite quantity. Each cubic foot of air that is forced up a chimney by heat, or blown out of a duct by a dryer, must be replaced. If the house is even loosely closed, the air for replacement can’t leak in easily, and a slight vacuum develops in the house. In cold weather, the natural buoyancy of warm air tends to make the vacuum in the basement stronger, and raise the pressure in the upper parts of the house. This is called ‘stack effect’. The net result is that the house is sitting on the soil like a big vacuum cleaner, sucking in soil gas. Soil gas consists of ordinary air and water vapor, but if there is a small amount of uranium in the soil, then radon will be part of this inflow.

Can’t we just seal out the soil gas? Well, we can try, but it’s nearly impossible. Radon, like water vapor, is quite capable of passing through the pores of solid concrete. It will come through cracks and holes if they are present, but it doesn’t need any visible opening at all. Trying to seal out radon from inside a basement is like trying to caulk a boat from inside the bilge. It just doesn’t work.

Good radon mitigation involves reversing the pressure gradient that drives radon entry. In other words, we must create a stronger low pressure zone in the soil below the basement floor slab than the house is creating above the slab. This is done by installing a small electric fan, and ducting the fan’s input side to the soil under the floor. The fan’s exhaust side is then ducted to the atmosphere. That’s basically it, the rest is details. There are some very critical details which prevent the radon from being pulled back into the house through other openings, prevent electrical problems, reduce energy consumption and noise, etc. These are laid out in the EPA’s Radon Mitigation Standards. People who are trained and tested in the art of mitigation are called Listed Radon Contractors. If you are hiring someone to fix a radon problem, be sure they are listed.

One more thing: A well-designed mitigation system does not exhaust house air, and the ventilation rate in the living area is not substantially affected! The air coming out of the mitigation pipe is coming from the soil under the basement floor. This is an important distinction. If we tried to reduce radon levels by actually ventilating the basement, the increase in heating and cooling cost would be enormous! This is why ‘just opening the windows’ is not a viable mitigation option. (Of course, in order to maintain the strength of the sub-slab vacuum field, the mitigator may seal cracks, holes, etc. in the floor. This may be where some people got the idea that crack sealing is mitigation.)

How much does mitigation cost? Typical costs for a basement installation are $800-1,200. Costs go up if the pipe needs special routing to improve appearance, if the house is partly basement and partly crawl or slab, or if the footprint area is over about 1,500 sq. ft. All-crawlspace or all-slab installations vary in cost. This writer’s first mitigation job involved a home with a small basement and large crawlspace. The cost was $1,900. The starting radon level in the basement was 57.2 pCi/l, and the post-mitigation level was 0.5 pCi/l. Yes, it really works! No, I’m no longer doing mitigation.

Most mitigation jobs are complete in a single work day. Most mitigators guarantee that the radon level will fall below 4 pCi/l, and stay there for a certain number of years.

Is this a do-it-yourself project? For a very capable d-i-y-er, it can be. If the idea interests you, get your hands on a copy of “Protecting Your Home from Radon” by D.L Kladder, published by Colorado Vintage Companies, Inc. 719-632-1215. Your local public library should have it, or know where to get it.

Qualified radon people . The EPA set up a radon proficiency program in the 1980’s to ensure that people who represented themselves as testers or mitigators met a minimum standard of competence. Apparently, EPA’s intent was to create the guidelines for training and certification, and then let the individual states enact statutes and programs to enforce them. EPA measurement protocols, mitigation standards and training requirements were, therefore, voluntary. Because any scam artist could still go out and sell fake radon services without breaking any laws, most states picked up the slack by turning EPA’s voluntary standards into enforceable statutes. In Ohio, for instance, anyone representing themselves as a radon contractor must be licensed, and maintaining a license means periodic training and testing. In September of 1998, the EPA saw its mission as complete, and shut down the Radon Proficiency Program. Michigan, however, had never set up any type of program for protecting its citizens from scam operators. This writer will refrain from commenting on the political bent that sees defrauding the public as an economic right that must be protected. The bottom line for Michiganians is caveat emptor! Here is how to eliminate the worst of your risk:

  1. Use the old EPA lists. Make sure your tester is listed either as a residential service provider, or analytical service provider, and that your mitigator is listed for residential mitigation. If your tester is using a monitor, make sure the listing has him or her marked for that type of device, not for charcoal cans.
  2. Ask for references. Check them.
  3. Look for membership in one or both of these organizations: National Environmental Health Association or the National Radon Safety Board. These industry groups have replaced the Radon Proficiency Program.
  4. Call the Better Business Bureau for your community.
  5. Don’t pay in full for the mitigation job until you are satisfied that it’s right and that the radon level is down where you want it. Call an independent tester to confirm that the system is working, or do the test yourself if time allows.
  6. Having read this article, you now know more about radon than most city building departments. They may want to check the wiring of the fan to see that it complies with electrical code. If the pipe system passes through the wall between a house and an attached garage, the city will want to check the fire wall protection at this point. That is about as far as most building departments will go.

Remember, there is one individual in southeast Michigan who carried all 3 EPA listings , now belongs to NEHA and NRSB, and is a fully-qualified home inspector: Matt Bezanson of Sherlock Homes Inspection, Ltd. There is no one better to call if you have any doubts about that radon test or system.!

This article contributed by:

mi_bezanson_matt_MAR06.jpgMatt Bezanson
Sherlock Homes Inspection, Ltd.
1820 Briarwood Drive
Madison Heights MI 48071

Contact Matt today to schedule an inspection!