It is always good to have a geiger-counter, a tool to measure ionizing radiation. I have a geiger-counter from Imagesco:
But I think there is something wrong with it, because some times it wouldn't react on high radiation. So I plan to buy this one, a gamma-scout:
But due the nuclear accident in Fukushima, Japan, the company has gain too many orders, so it would take time to get one.
Once I borrowed a very, very expensive geiger-counter from a hospital. It was very accurate, but it costed about $ 12 000.
Radiation can be measured in many ways. Here is a simple explanation of the different units.
One decay per second is 1 Bq, it is the standard unit for decaying.
Curie is an older unit. 1 Ci is 3,7 x 10^10 Bq, which be equivalent to the decay of 1 gram of Radium.
Coulomb per kilo. Coulomb is a measure of electrical charge. 1 coulomb is the charge of by one second passes a conductor with the current of 1 ampere.
Roentgen (R) is an older unit, which be equivalent to 0,000258 C/Kg
1 Gy is one joule per kilo. One joule is equivalent to move one coulomb, one meter with one volt.
Rad is an older unit, 1 rad is 0,01 Gy.
1 Sv is absorbed dose (in gray) multiplied with the quality-factor. The qulity factor is, for;
α-radiation = 20
β-radiation = 1
γ-radiation = 1
n-radiation = 5-20 depending on the energy
Rem is an older unit, 1 rem is equivalent ro 0,01 Sv.