On the web I have found several pages crediting Ernest Rutherford with the invention or at least with discovering the foundation of efficient smoke detectors. The story often goes like this:
The modern smoke detector, responsible for saving so many lives in house fires, can be traced back to 1899 when, at McGill University in Canada, Rutherford blew tobacco smoke into his ionisation chamber and observed the change in ionisation. (source)
Many more can be found with a Google search. However, Wikipedia tells a similar story about the Swiss physicist Walter Jaeger, without mentioning Rutherford at all:
In the late 1930s the Swiss physicist Walter Jaeger tried to invent a sensor for poison gas. He expected that gas entering the sensor would bind to ionized air molecules and thereby alter an electric current in a circuit in the instrument. His device failed: small concentrations of gas had no effect on the sensor's conductivity. Frustrated, Jaeger lit a cigarette—and was soon surprised to notice that a meter on the instrument had registered a drop in current. Smoke particles had apparently done what poison gas could not. Jaeger's experiment was one of the advances that paved the way for the modern smoke detector.
I tend to be on Wikipedia's (and Jaeger's) side: I find it likely that, Rutherford being such a well known scientist, some discoveries may be falsely attributed to him. But I wonder if someone can settle the issue with some trustworthy reference.