Before discussing test methods, it is important to note that it is our opinion, that all existing test methods are capable of "False Positive" under certain conditions.

    In an example, a scenario in which the new tenant of a building wants to increase production space into an area that was a warehouse floor. Inexperienced people did a concrete underfloor inspection on the floor with a calcium chloride test and found the results met the criteria required by the selected floor covering manufacturer and recommended that installation proceed.
    Soon after, the flooring failed, and new tests had to be ordered. The new tests revealed moisture vapor emission levels higher than the original results.
    
   The concrete surface of a warehouse will become dry and moisture vapor emission levels will be low enough to pass the requirements of a floor manufacturer. However, once covered, the moisture content in the concrete begins to rise and can cause failure of the flooring.

    We have not yet seen this difficulty when testing with in-situ relative humidity probes, but there should be concern when covering concrete that is not protected by an effective moisture barrier or vapor retarder.

    My opinion is that a combination of tests, performed concurrently in/on a subject floor, offer the greatest depth of data and confidence in a decision that may be made based on such data.
   
    When a single test is specified, it is our opinion that calcium chloride tests are best used as a tool in failure investigations, and in-situ relative humidity tests are pre-installation predictors of moisture related floor covering failure.

Now, Let's decide...