Limits and uncertainties--with special regard to radon measurements.

The concept of limits was introduced to assure a commonly tolerated low health risk from the exposure to radioactivity or chemicals. In most countries concentration limits are given by the authorities and are fixed to certain values. The question is how to prove compliance with limits, keeping in mind that all measurements are subject to uncertainties. This means there is always a certain probability for a wrong decision. Generally, the authorities demand only the answer "below" or "above" the limit and will not accept statements on probability. Advantages and disadvantages of different decision making philosophies are discussed.