How To Look At A House

McGarry and Madsen's home inspection blog for buyers of  

site-built, mobile/manufactured and modular homes

Can a mobile/manufactured home have a high radon problem?

Friday, July 20, 2018

This is what the United States Environmental Protection Agency (EPA) has to say about mobile homes and radon: “Unless these buildings are set up on piers without any skirting placed around them, interior vacuums can cause radon to enter these types of homes as well.” So, the EPA confirms that it is possible for a mobile home to have elevated radon levels. But, as we will explain later, it is less likely than in an average site-built home.

    People that have heard about radon, but don’t know too much about it, typically fall into one of two camps. Either they think it’s a deadly gas and, if you have it in your home, you are doomed; or that it’s nothing to worry about, just some psuedo-science mumbo-jumbo that’s been blown out of proportion by the media. The truth falls between those two extremes.

    Radon is a colorless, tasteless, odorless gas that is a Class A carcinogen, and the second leading cause of lung cancer, after smoking. Radon comes from the radioactive breakdown of naturally occurring uranium and radium, found in most soils. It’s important to know that a low level of radon is in the air we breathe every day, even outdoors. The health risk occurs when high levels of radon accumulate in a home.

    The “interior vacuums” that the EPA refers to in their official radon statement is the natural chimney-effect that occurs in almost any home. The air pressure difference between the interior and exterior of a home draws in air around the bottom, then exhausts it through the upper portion. The diagram below shows how it works.     Radon starts as a gas in the soil, and rises up into a site-built home through the inevitable cracks and small openings in the foundation, basement, or floor slab. But most manufactured homes have an advantage in that they are elevated, the crawl space has some ventilation, and the bottom of the home is sealed with the plastic sheet “belly board”—that is, as long as the ventilation is not blocked and the belly board remains intact and sealed. Also, some mobile homes have a plastic-sheet vapor barrier on the ground under the home that further limits radon. These built-in features can reduce the amount of radon that enters a manufactured home compared to a site-built home with a similar amount of radon in the soil below it. But, if there is a high level of radon to begin with, you may have an unsafe level of radon inside your home anyway and mitigation would be necessary.

    Radon is measured in pico-curies per liter of air, and 4.0 pCi/L or higher is defined by the EPA as an unsafe level of interior air. If you live in an area of the U.S. known as having elevated radon readings, we recommend testing with a simple home-test kit available at most hardware and home improvement stores. In our area of Florida, Alachua County maintains a website with a map indicating the areas of the county that have been found to have high radon ( Many other parts of the U.S. have similar maps for your reference. Also, the U.S. Environmental Protection Agency’s radon homepage is at for more information on radon.

Here’s links to a collection of our blog posts about “RADON":

 Is a radon mitigation fan required to be on a dedicated circuit breaker/fuse in the electric panel?

What happens to a radon test result if the windows were opened, the test device moved, or there was any other evidence of tampering during the test? 

Where do I find the Florida laws regarding radon?

Can I test vacant land for radon before building a house? 

Is radon mitigation possible for a condominium?

Do radon mitigation systems require maintenance?

What is the average life expectancy of a radon mitigation system?  

Do older houses have higher radon levels than new houses? 

Can the seller tamper with a homebuyer's radon test to change the results?

How long does it take to get the results of a radon test? 

Will opening the windows reduce the radon level in a house?

How was it determined that between 15,000 and 22,000 lung cancer deaths each year are caused by radon?

Can a homebuyer do their own radon test for a real estate transaction with a self-test kit?

What is the danger of radon in well water?

What are the symptoms of radon poisoning? 

Does Florida have radon?

Where does radon come from? 

For how many years does an old radon test result remain valid?

Should homeowners get a pre-listing radon test before selling their home?

What are a homebuyer's options when the radon test comes back high (4.0 pico-curies/liter or more)? 

Do granite countertops emit radon?

How can I tell if a house has a radon mitigation system? 

Do I need to test for radon when buying a condominium? 

What does a radon mitigation contractor do to lower the radon level in a home?

How can not testing for radon be an expensive mistake for homebuyers? 

Will the radon test come back sky-high in a house that has been empty and closed-up for months? 

What is radon? Should I be concerned about it?

Should I buy a house with a high radon level? 

What is the average radon level of indoor and outdoor air in America?

What is the operating cost of a radon mitigation system? 

• Should I buy a house with a radon mitigation system?

• Does the buyer or seller of a home pay for radon mitigation when the radon test comes back high? 

What is the probability of having high radon in a Florida house?

• How quickly do I need to reduce a high radon level in my house? 

Does a home inspector check for radon?

What are the problems with underground return air ducts? 

• What is the probability of having high radon in a Florida house?

• What factors can change radon test levels up or down?

    Visit our RADON and MOBILE/MANUFACTURED HOMES pages for other related blog posts on this subject, or go to the INDEX for a complete listing of all our articles.

Water Heaters

Water Heater Age

"What Are The

Signs Of..."

Septic Tank Systems

Structure and Rooms

Plumbing Pipes

Termites, Wood Rot

& Pests



When It First

Became Code

"Should I Buy A..."

Park Model Homes


Shingle Roofs




Wind Mitigation

Roof and Attic

"Does A Home


Pool and Spa

"What Is The Difference Between..."




Concrete and

Concrete Block

Metal Roofs


Modular Homes

Rain Gutters

Mold, Lead & Other Contaminants


Older and

Historic Houses

Crawl Spaces

Mobile-Manufactured Homes

Building Permits

Life Expectancy

Clay Soil





Exterior Walls

& Structures


Common Problems

HUD-Code for

Mobile Homes

Garages and Carports

Flat (Low Slope) Roofs

Electrical Panels

Sprinkler Systems

Electrical Receptacle Outlets

4-Point Inspections

Hurricane Resistance

Frequently Asked Questions (FAQ)

Home Inspection

Heating and Air Conditioning

Building Codes

Fireplaces and Chimneys

Inspector Licensing

& Standards

Energy Efficiency

Washers and Dryers



Doors and Windows



Electrical Wiring

Click Below  

for Links

to Collections

of Blog Posts

by Subject

Plumbing Drains

and Traps


Smoke & CO Alarms

Aging in Place

Top 5 results given instantly.

Click on magnifying glass

for all search results.






Air Conditioner & Furnace Age/Size


Electrical Switches





Water Intrusion

Electrical - Old

and Obsolete


Foundation Certifications

Tiny Houses

About McGarry and Madsen



Buying a home in North/Central Florida? Check our price for a  team inspection by two FL-licensed contractors and inspectors. Over 8,500 inspections completed in 20+ years. In a hurry? We will get it done for you.

Moisture Problems

Crawl Spaces