There have been a number of cases where electrosensitive individuals have been badly affected by smoke alarms, when they develop severe symptoms of electrosensitivity that seem to last longer than those from exposure to weak non-ionizing electromagnetic radiation. The most likely cause is that the cheap “ionizing” type of smoke alarm contains a radioactive isotope (Americium-241) that gives off small amounts of gamma rays that can trigger electrosensitive responses.
Americium-241 emits both alpha particles and gamma rays. The alpha particles ionize the air in a chamber inside the device, which allows it to conduct electricity from the battery. When smoke enters the chamber, it combines with these ions to neutralise them, which reduces the flow of current and sets off the alarm. The alpha particles cannot travel far through air and are contained within the casing of the alarm, but the gamma rays are more penetrating and escape to the outside.
Gamma rays damage the fatty components of cell membranes (in effect they go rancid) and the membranes leak. When this occurs in sensory cells, they trigger the release of neurotransmitters, which stimulate neighbouring nerve cells to send false signals to the brain. This then gives symptoms of electrosensitivity. Electrosensitivity to non-ionizing electromagnetic fields; e.g. from mobile phones, is probably due to membrane leakage caused by the temporary removal of some of the calcium ions that normally stabilise them, and is more rapidly reversed.
If you find you are affected by these devices, the best solution is to buy one or more “optical” smoke detectors. These contain no radioactive isotope. Instead, smoke entering the device interrupts a beam of infra red light and it is this that sets the alarm off. They are more expensive and the batteries may not last so long, but they are less likely to give false alarms when there is no significant smoke; e.g. from cooking or burning the toast.
Andrew Goldsworthy 2010