Academic journal article Journal of Environmental Health

Mold Can Grow in the Absence of Visible Moisture Intrusion

Academic journal article Journal of Environmental Health

Mold Can Grow in the Absence of Visible Moisture Intrusion

Article excerpt

A source of mold may be hidden right underfoot. Under many floors are concrete slabs that give off water vapor. If this release of moisture results in high-enough relative humidity, flooring can fail and mold can grow. It is essential, then, to ensure that concrete slabs are sufficiently dry before flooring is added and that air movement is adequate to prevent high relative humidity.

One traditional and widely accepted test for water vapor emission uses calcium chloride. In this test, a plate of calcium chloride is weighed, then placed on the concrete and covered by a dome or other apparatus to trap the moisture vapor. The dome is sealed to the concrete to prevent ambient influence or loss of vapor. The testing materials are left untouched for 60 to 72 hours, during which time the calcium chloride absorbs water vapor. At the end of the test period, the plate is again weighed. The difference in the starting and ending weights is used to determine the vapor emission volume. ASTM International Standard F1869-98 covers this method. …

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