Geiger-Counter Measurements in a Montgomery County, Maryland Home

Radiological monitoring of ambient indoor household radioactivity, appoximately 25 miles NW from Washington, D.C. in western Montgomery County, Maryland . Updates to this web site are approximately biweekly unless something interesting is going on.   For information about the detector, environment and data click here. Disclaimer: This is a private homeowner-created website and the content was not produced by an expert in gamma or radon measurements. The existence of this website and its content are at the whim of the homeowner and are not sponsored by nor representative of any commercial, government, or other private parties.

A typical background count level is about 13.5 to 14 counts per minute if windows are open and can become as high as 22 counts per minute when windows are closed.

LATEST WEEK

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CURRENT MONTH

The 2-sigma uncertainty for background data plotted as 2 hour averages is about 5%.

Radioactivity Data Archives:

• 2007 (includes commercial radon tests and window effect)
• 2006 (includes interesting background change and tests)
• 2005 (includes interesting diurnal patterns)
• 2004 (includes some strong diurnal patterns)
• 2003 (includes interesting weather events)

Peaks above background, in order of intensity: with estimates of background-subtracted counts per minute (cpm). A typical background is about 13.5 cpm. The values shown below are in excess of the background.

• 35 cpm - Nov 19 2003 ~ 2am (rain)
• 25 cpm - Dec 10 2003 ~midnight (rain)
• 23 cpm - Oct 26 2003 ~9am
• 23 cpm - Jan 14 2005 ~ 10am (rain)
• 19 cpm - Mar 02 2007 ~ noon (rain)
• 17 cpm - Sep 23 2003 ~3pm (rain)
• 11 cpm - Nov 05 2003 ~5pm (rain)
• up to about 10 cpm, eg. February 2007 diurnal peaks
• 6.0 cpm - Sep 15 2004 ~ midnight (rain)
• 5.5 cpm - Jun 30 2005 ~ 9am
• 3.5 cpm - Jul 07 2005 late morning
• 3 to 3.5 cpm - Sep 11,13,14 2005 early morning (unusually high diurnal peaks during local drought)
• Unusual plateau- shaped peaks instead of normal spike peak shape: +2 cpm from Oct 22 to 23 2006, then steadily 2 cpm higher than normal for 2 or 3 days, then another jump up making it +3 cpm higher than normal.

Relationship to weather: The baseline tends to have an inverse relationship with outdoor barometric pressure. The diurnal peaks tend to have a direct relationship with outdoor winter temperature (at least in late winter). Occasionally, peaks will correspond to preciptation (see list above). Compare plots to weather archive of nearby Leesburg VA (use text box and period such as daily, weekly, monthly, to select dates of interest). These relationships are tendencies only.

Relationship to radon: Alpha exclusion testing and weather information suggest the baseline is mostly composed of the non-alpha (essentially non-radon) component, probably dominated by cosmic radiation, and the daily peaks, when present, are largely due to alpha (Radon etc.) activity.

Other sites with radiation / radioactivity data:

The background image is adaptated from a Lawrence Berkeley National Laboratory historical bubble chamber image.

Comments about this web site and radiological data may be e-mailed to zeissler{at}aol{dot}com.