For each of the critical water quality parameters alert levels and action levels have been set based on past experience.

Finland and Canada use 20 picocuries as their action levels.

If the 90th percentile value of all the samples exceeds the action level, action must be taken.

It matters not at all that other nations may have selected higher action levels for their populations.

One in five of all school rooms was found to have radon levels at or above the recommended action level.

Even Weick doesn't make it clear that this dilemma is not found only at the action level.

This measure sharply lowered the previous action level of 150 parts per billion that was established in March 2002.

"Evidence suggests that radon is a national health problem and we'd like this action level to be even lower," he said.

If more than 10% of tap water samples exceed the action level, water systems must take additional steps.

Your result is so close to the action level, that it cannot be said with certainty that the home has a radon problem.