Answer to Question #1502 Submitted to "Ask the Experts"

Q

I recently had my home inspected for radon gas. The tester set up the electronic measuring device directly underneath (within 1 meter) a ceiling-mounted smoke detector. The smoke detector contains a 0.9 microcurie dose of ²⁴¹Am which I believe is an alpha emitter. Could this have caused a slight increase in the radon reading? The reading came back at 8.3 picocuries.

A

No. The americium source in the smoke detector does, as you say, emit alpha particles, but it should not affect the radon-monitoring device. While the operation of some radon-monitoring devices can be affected by high humidity and/or air currents, a professional should be aware of such potential problems when deploying the equipment. Keep in mind that there are many things that can cause the indoor radon concentrations themselves to vary—that is why the Environmental Protection Agency (EPA) recommends that homeowners perform, if possible, long-term measurements rather than rely on short-term measurements. Some of the things that affect the indoor radon concentration include the type and operation of the building's ventilation system and anything else that can affect indoor air pressure (for example, window openings, window fans, operation of driers, fireplace use), weather (for example, wind speed), and in some extreme cases, even water usage if the water comes from a private well. Radon levels can depend on the time of day—they are usually highest in the early morning. They also vary from one part of the home to the next—radon concentrations are usually highest in the lowest levels of the home, for example, the basement. If you have not done so already, it would be worth looking at the EPA's "A Citizen's Guide to Radon." It can be seen at the EPA's radon publications Web site. Paul Frame, CHP, PhD