|Symbol||Penetrating power||Ionising power||Range in air|
|Alpha||α||Skin/paper||High||< 5 centimetre (cm)|
|Beta||β||3 mm aluminium foil||Low||≈ 1 metre (m)|
|Gamma||γ||At least 40 mm lead or 2 m concrete||Very low||> 1 kilometre (km)|
One example of a use of alpha radiation is in smoke detectors. A source of alpha radiation is used because the range is very low and alpha radiation has a very high ionising power.