Radioactivity can not be detected with our five senses, special detectors are needed to tell us we are being exposed to it therefore it is particularly dangerous. People may unknowingly be exposed to it for prolonged periods of time with a detrimental effect on their tissue and genetic material.

Several devices have been developed to detect radioactivity, with the earliest being an unexposed photographic plate placed in the vicinity of a source being detected.

Other devices include:

cloud chambers,

electroscopes,

ionising chambers,

the Geiger-Müller tube,

liquid and electronic bubble chambers,

scintillation detectors (spinthariscope), and solid state semiconductor devices.