Quality Assurance & Quality Control
Introduction to Radon Mitigation
Worker Health & Safety
2 of 3

Residential Measurement Protocols

The scope of this course addresses residential radon testing which carry two primary protocols to determine the presence of elevated radon levels indoors and the subsequent need for mitigation:

  1. Extended [non real estate transactions]
  2. Time Sensitive [real estate transactions]

A) Extended Testing

A residential test conducted for a concerned homeowner not involved in a real estate transaction should begin with a short-term test under closed-building conditions and followed up with an additional short-term test in an opposite season or a long term test in order to determine the need for mitigaiton. The protocol for follow-up testing is as follows:

Initial Short-Term Test ResultFollow-Up [Extended] Test ProtocolNotes
Between 4.0 pCi/L and 8.0 pCi/LShort-term or long-term testConduct follow-up testing in an opposite season when possible.
Over 8.0 pCi/L [more than double the action level]Short-term test 
Below 4.0 pCi/LRetest every 5 years See Section 4.3.1When initial results are between 2.0 pCi/L and 3.9 pCi/L, consider a follow-up test during an opposite season.
The results of any two tests may be averaged and used to determine the need for mitigation.The results of any two tests may be averaged and used to determine the need for mitigation.
Chart 4-1 
Action Steps for Extended Test Protocol [Follow-Up Testing]

B) Time-Sensitive Testing

Due to the time-sensitivity of a real estate transaction, radon tests should begin with a short-term test under closed-building conditions to a achieve results quickly.  Since radon levels tend to vary from day to day and season-to-season, a short-term test is less likely than a long-term test to reveal the year-round average radon level. However, the assumption is that since the short-term test is conducted under closed-building conditions a low reading is likely to mean the annual average will also be low and a decision can be reasonably made whether or not mitigation efforts should be taken.

A radon measurement conducted during a time-sensitive real estate transaction carries a unique set of protocol due to the multiple parties and financial interests involved. Typically, the measurement professional is hired by the buyer in a real estate transaction to test a property that is controlled by another party with financial interest.  Using due diligence in the real estate transaction test is imperative in order to obtain the most accurate results possible in the least amount of time allowed.   Lack of diligence could result in devastating affects to the buyer and/or seller.  A buyer who receives a false-low reading will live in a home that is otherwise thought to be free of a radon problem.  The buyer who receives a false-high reading may ask the seller to fix the home unnecessarily. Two unique protocols exist for conducting radon tests involved in a real estate transaction [time-sensitive].

Option 1:  Simultaneous Testing with Passive Devices

  • Simultaneous testing must be comprised of a minimum of 2 indoor radon measurements conducted in duplicate with similar measurement devices, placed and retrieved on the same date and time.

Option 2:  Continuous Monitor Testing

  • This option requires an active continuous monitor that has the capability to integrate and record a new result at least hourly.  Shorter integration periods and more frequent data logging afford greater ability to detect unusual variations in radon or radon progeny concentrations…

Options for Testing in Real Estate Transactions

OptionMethodSpecial Device ProtocolsAnalysis & Interpretation
1Simultaneous Testing w/ 2 Passive Devices          [Time Integrating Devices]Co-located and spaced 4 to 5 inches apartExposed for the same measurement periodProduce results in same units (pCi/L or WL)Report individual results and overall average as a determination for mitigation.
2Continuous Testing w/ Active Devices [Continuous Monitors]One continuous monitor may be deployed in lieu of 2 passive devices. Must be able to integrate, record, and produce hourly readings.Single result is sufficient as a determination for mitigation.
Chart 4-2
Test Protocol for Real Estate Testing [Time-Sensitive]

Note: It is universally recommended that all initial testing begin with a short-term test [time-sensitive protocols] conducted under closed-building conditions to alert residents quickly if elevated concentrations of radon are present in the home. Follow-up testing conducted under extended test protocols, is recommended to confirm the initial test results.

Deployment and Retrieval Protocols

Device Location

At the very least, a radon measurement should be conducted in the lowest structural area suitable for occupancy over each foundation. For example, a split level building with a basement, a slab-on-grade room and a room over a crawlspace must have measurements made in each foundation types: the basement, a slab-on-grade room and a room over the crawlspace.  Regardless of whether multiple testing locations are required, devices should be put in a room that is used regularly (like a living room, playroom, den, or bedroom). Charcoal devices must not be placed in kitchens, laundry rooms, spa rooms or other areas of high humidity.

In general, the following placement protocols are universally accepted.  However, individual state regulations supersede any recommendation made in the following section.

Measurement devices must be:

  • Placed in rooms that can be regularly occupied, such as family rooms, living rooms, dens, playrooms and bedrooms.
  • Undisturbed during the measurement period
  • At least 4 inches away from other objects horizontally or vertically above the detector
  • At least 3 feet from exterior doors or windows to the outside
  • Out of the direct flow of HVAC vents, ventilation ducts, or fans
  • Away from surfaces made of natural stone that may emanate radon [e.g. natural granite counter tops, hearths, or slate pool tables].
  • One test location per 2000 square feet is required for all test areas over 2000sf.
  • At least 1 foot from exterior walls
  • At least 20 inches from the floor
  • At least 1 foot below the ceiling to less than 8 feet above the floor

Note: Charcoal devices should not be placed in bathrooms, kitchens, laundry rooms, spa rooms or other areas of high humidity, closets, cupboards, sumps, crawlspaces or nooks within the foundation.

Closed-Building Conditions [CBC]

The following CBCs should be initiated at least 12 hours prior to any test lasting less than 96 hours and for the duration of any test lasting less than 7 days.

  • Keep closed
    • Windows, except when being momentarily opened/closed during a home inspection.
    • Doors leading to the garage, except for normal exit/entry
    • Doors leading to the outside, except for normal exit/entry
    • Fireplace Dampers
  • Do not operate:
    • Whole House Fans
    • Window Fans [seal shut]
    • Fireplaces [except when serving as the primary source of heat]
    • Any system that temporarily draws air into or out of the building
    • Evaporative Coolers [aka Swamp Coolers]
    • Portable Window Air Conditioners in Fan or Vent Mode
  • Operate Minimally:
    • Clothes Dryers
    • Range Hoods
    • Bathroom Fans
  • Operate Normally:
    • Permanently Installed HVAC Systems
      • Normal operating condition/temperature:  65 – 80 degrees
    • Dehumidifiers, Humidifiers
    • Central Vacuum Systems
    • Portable Air Cleaners
    • Crawlspace dehumidification system vents
    • Attic Fans
    • Permanently Installed HRV/ERV Systems
    • Radon Mitigation Systems
    • Portable Window Air Conditioners in Recirculation Mode
  • Structural openings due to disrepair or structural defects must be repaired.

Protecting the Chain of Custody

All devices, whether for radon gas or working level measurements, should be tracked and custody information logged including:

  • Address of measurement client and building measured
  • The start and stop, date and times of each measurement
  • The detector type and identification numbers
  • Compliance or Non-Interference Agreement
  • Exact placement location of the detector