By March 1, 2014, all residential rental property in Maine must be tested for the presence of radon. Radon is a naturally occurring radioactive gas which results from the normal breakdown of uranium found in most rocks and soil and which has been proven to cause lung cancer. Though the law requiring radon testing, 14 M.R.S. 6030-D, took effect in September of 2009, landlords have until March 1st to test their properties and report the results of such testing to the Department of Health and Human Services. While landlords may test “simple” buildings, all other testing must be conducted by a Maine-registered radon tester. A simple building is defined by statute as a building which does not have any of the following: (1) an elevator shaft, (2) an unsealed utility chase or other open pathway for air to move from the ground to upper levels of the building, (3) a forced hot air furnace or central air HVAC system, or (4) private well water (unless the water has been tested by a registered radon tester and results show an acceptable radon level). A payroll employee of a landlord may test on his or her behalf but the statute does provide that a contract property manager must first become a registered radon tester before they can test for radon. Tenants may also test the rental unit themselves. Not every unit in a multi-family building must be tested under the statute. Testing is required for each unit that is in contact with the ground; if the building has a basement, crawl space, parking garage or commercial space below the residential rental units, each unit on the lowest level of residential units must be tested. The radon testing protocols also require the testing of 10% of units on each upper floor; when there are fewer than 10 units on upper floors, this means that at least one unit on each upper floor must be tested.