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Environmental Consultations

Radon in Multifamily Buildings

No conflict of interest:  Potomac Homes is an independent, locally owned and operated business, providing only radon measurement services and with no links to and no interferences from radon remediation contractors.

We are using the Protocol for conducting Radon and Radon Decay Product Measurements in Multifamily Buildings, developed by the AARST Consortium on National Radon Standards, an approved American National Standard (ANSI).



AARST-ANSI Protocol for conducting Radon and Radon Decay Product Measurements in Multifamily Buildings (MAMF-2010):
3.0 Where to Test

3.1 Conduct a measurement in each ground contact apartment, dwelling and those rooms that are used as office space. This means each unit that has floor(s) and/or wall(s) in contact with the ground or is over crawlspaces, utility tunnels or parking garages.

Within each dwelling, test a room located in the lowest livable level that is in contact with the ground or above a crawlspace, utility tunnel or garage. If the lowest level is not currently used but could serve as a den, playroom, office, work area or an additional bedroom at some time in the future, conduct a test in this level.

(See placement example diagrams in Exhibits 1a and 1b.)

3.2 Also conduct a measurement in non-residential ground-contact rooms or areas (e.g. utility rooms, storage rooms, and maintenance rooms) that:

  • are occupiable with little or no modification; or
  • have air communication with occupiable areas (e.g. stairwells and elevator shafts).

When in doubt, test the area. Results from testing these unoccupied areas provide assurance regarding current or future use of the building, and they may indicate a need for additional testing in upper areas. These unoccupied areas may serve as a pathway for radon into apartments and offices of upper floors.

3.3 For large rooms or open areas - Place one detector every 2,000 square feet (186 square meters) (e.g., a square area with each side 45 feet (13.7 meters) in length).

3.4 On the upper floors, conduct a measurement in at least one apartment on each floor; include measurements in at least 10 % of the dwellings on each of the higher floors. It is recommended that the upper floor test locations be selected so that units on one floor are not directly above or below units being tested on other floors. (See placement example diagrams in Exhibit lc.)

3.5 Test all areas during the same time period (days or phase).

Section III: Protocol For Multifamily Measurement Section III: 2

Do you know what you are breathing?

It is highly recommend to measure the indoor concentration level of radon in Montgomery, Howard, Frederick counties, in Northern Virginia and in the District of Columbia

Please contact us for detailed estimates 


The EPA recommends that you fix your home when the radon level is 4 pCi/L or more and we suggest that you contact a qualified radon reduction contractor about lowering the radon level if results of the above tests are over this threshold.


Another level set by the EPA is 2.0 pCi/L ("Consider Action Level"). At this level, the EPA recommends that you consider installing radon abatement systems in your home to reduce your indoor radon levels.

[more about radon]


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Last modified: 07/11/2017

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