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 more of our blog posts with useful information about buying and owning a mobile home:

  1. Does it make sense to buy an older mobile home and remodel it?

  2. Where do I find the vehicle identification number (VIN) on a mobile home?

  3. How do I find out how old a mobile home is and who manufactured it?

  4. What is the life expectancy of a mobile home?

  5. What are the most common problems with older mobile homes?

  6. What is the right price for a used mobile home?

  7. What does the HUD tag look like and where do I find it on a mobile home?

While we hope you find this series of articles about home inspection helpful, they should not be considered an alternative to an actual home inspection by a local inspector. Also, construction standards vary in different parts of the country and it is possible that important issues related to your area may not be covered here.
© McGarry and Madsen Inspection


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More Blog Posts on Radon:

  1. What is radon? Should I be concerned about it in Gainesville?

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

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

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

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

  6. What’s my chance of getting a high radon reading in Gainesville?

  7. What is the danger of radon in well water?

  8. This house has been empty and closed-up for months. Will the radon test come back sky-high?

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

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

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

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

  13. Can the seller tamper with a homebuyer’s radon test to change the results?

  14. What is the operating cost of a radon mitigation system?

  15. Should I buy a house with a radon mitigation system?

Here’s links to some of our other blog posts about mobile homes:

  1. How can I make my mobile home look more like a house?

  2. How can I tell the difference between a manufactured
    home and a modular home?

  3. How much does it cost to move a mobile home?

  4. What can I do to prevent dampness and mold in my mobile home?

  5. How can I tell if a mobile home is well constructed?

  6. What is the plastic sheet called that covers the underside of a mobile home?

  7. Why is there such a big gap under the doors inside a mobile home?

  8. What are the warning signs of a dangerous deck?

  9. What size air conditioner is right for my mobile home?

  10. Does an addition to a mobile home have to comply with the HUD Code?

  11. What’s the difference between a manufactured and a mobile home?

  12. What is a Park Model mobile home?

  13. How can I remove water under my mobile home?

  14. Where do I find the Vehicle Identification Number (VIN) on a mobile home?

  15. How much does a mobile home inspection cost?

  16. Can I install a mobile home myself?

  17. What is the stuff you paint on an old mobile home metal roof to extend its life?

  18. How fire-resistant is a mobile home?

  19. What are the tie-down requirements for a mobile home?

  20. What’s the difference between a trailer, a mobile home, a manufactured home, and a modular home?

  21. How can I upgrade a wind zone 1 mobile home to wind zone 2?

  22. Can I put a zone 1 mobile home in Florida?

  23. Are house numbers required by law in front of a house?

  24. Can you move a mobile home that is 20 years old in Florida?

  25. What is a pit set mobile home?

  26. Does a single-wide mobile home have interior bearing walls?

  27. Is 7 feet a normal height for a wall/ceiling in a mobile home?

  28. Do you have any tips for buying a used mobile home?

  29. Why is the floor tile cracked in my mobile home?

  30. Why is it important that a mobile home stay level throughout its lifetime?

  31. How much venting is required for mobile home skirting?

  32. What is the average lifespan of a wood deck?

  33. What is the life expectancy of a modular home?

  34. How do I upgrade my old mobile home to meet HUD standards?

  35. Why is my double-wide considered a HUD home?

  36. How energy efficient is a mobile home?

  37. Can I tell the year of a manufactured/mobile home from the HUD tag (red tag)?

  38. When were the first double-wide mobile homes manufactured?

  39. What are the HUD requirements for selling a remodeled or renovated mobile home?

  40. How many mobile/manufactured home manufacturers are licensed to sell their homes in Florida?

  41. Can a mobile/manufactured home get termites?

  42. What are the limitations on homesites where a mobile/manufactured home can be located?

  43. What does a home inspector look for when examining a mobile home crawl space?

  44. How do I look for mold in my mobile home?

  45. What is the difference between the electric service to a mobile home and a site built home?

  46. How can I make my mobile home more energy efficient?

  47. What are the ventilation requirements for bathrooms and kitchens in mobile homes?

  48. How much is a used mobile home worth?

  49. What would cause half of a double-wide mobile home to lose electric power?

  50. How do HUD-code mobile/manufactured home standards compare to the IRC building code for site-built homes?

  51. What are the right words for the parts of a mobile/manufactured home?

  52. What is the difference between a manufactured/mobile home water heater and a regular water heater?

  53. What is a manufactured home?

  54. What is the building code for mobile/manufactured homes in Florida?

  55. Where do I find the VIN/serial number on a very old (pre-1976) mobile home?

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

  57. Can stormy weather change the radon in a house?

  58. Do older houses have higher radon levels than new houses?

  59. Do radon mitigation systems require maintenance?

  60. Is radon mitigation possible for a condominium?


Welcome to our blog!
We want you to be an informed homebuyer, and each blog post is a question that we have answered for our friends and customers over the years. Hope they help you make a good choice for your next home.

Radon Testing


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