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https://www.nist.gov/history/radiation-physics-building/facilities/radon-calibration-facility

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NIST History

## Radiation Physics Building

-  Staff  Expand or Collapse    -  Martin Berger 
  -  Randall S. Caswell 
  -  Louis Costrell 
  -  Margaret Ehrlich 
  -  Evans V. Hayward 
  -  Raymond W. Hayward 
  -  John Hubbell 
  -  Herman William Koch 
  -  James E. Leiss 
  -  Robert Loevinger 
  -  Robert Madden 
  -  Wilfrid B. Mann 
  -  William L. McLaughlin 
  -  Joseph W. Motz 
  -  Harold Wyckoff 
-  Facilities  Expand or Collapse    -  Cobalt-60 Pool Source 
  -  Isotope Separator Laboratory Facility 
  -  Linac 
  -  Mammographic X-Ray Facility 
  -  Manganese Bath Facility 
  -  Positive-Ion Van de Graaff Accelerator 
  -  Radon Calibration Facility 
  -  Synchrotron Ultraviolet Radiation Facility 
  -  The Curiously Colorful Wall of NIST's Radiation Physics Building 
  -  Construction 
-  Research Highlights  Expand or Collapse    -  External Beam Radiotherapy 
  -  Hazards From Radioactivity in the Environment 
  -  Neutron Spin Filters 
  -  Nuclear Medicine 
  -  Nuclear Theory and Radiation Data 
  -  Radiation Detection Standards for Homeland Security 
-  Modernization 
-  Colloquium Talk 
-  Credits 

# Radon Calibration Facility

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Radon-222 is a naturally occurring radioactive byproduct of radium-226. Radon is a known carcinogen, and the radon detection and mitigation industry depends on accurate environmental measurements. The National Institute of Standards and Technology (NIST) and its predecessor, the National Bureau of Standards (NBS), have provided the national standards for radon measurements and calibrations since the 1940s. 
Credit:

Today’s primary radon-222 calibration system, introduced in the early 1990s, is a modernized and expanded version based on the design of the original system from the 1940s. At the time this new system was being designed, consideration was given to possibly selecting an alternative measurement method for use as the primary standard. However, despite the passage of 50 years, researchers did not find any other available method or instrumentation that was more advantageous or superior to the original pulse ionization chamber. 

Credit:

In this pulse ionization design, a gas-filled chamber with a cathode and anode measures the charge from the number of ion pairs created within the gas by the emission of alpha particles (two protons and two neutrons, identical to a helium nucleus) from radon and its radioactive daughters. In a pulse ionization chamber, a separate electrical pulse is generated by each alpha particle.
Credit:

## Read about Marie Curie and the history of radon measurements at NIST.

PhysicsRadiation

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