Concrete Moisture Vapor Emission Rate from a Calcium Chloride Test (ASTM F1869)
The moisture vapor emission rate a calcium chloride dome test gives, and whether it is under the flooring maker's limit.
Example
You enter
- Calcium chloride mass gain (g) 3
- Test area as the kit states it (sq ft) 0.44486
- Exposure time (hours, 60 to 72 by the standard) 72
- Flooring or adhesive maker's limit (lb per 1,000 sq ft per 24 h) 3
- Floor area to be covered (sq ft, blank to skip the test count) 2400
You get
- Moisture vapor emission rate 4.956 lb per 1,000 sq ft per 24 h
- Margin (lb) -1.95577
- Tests the standard asks for 5
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeASTM F1869's arithmetic is a unit conversion: the grams the desiccant gained, turned into pounds of water per 1,000 sq ft per 24 hours over the test area and the hours it sat. A 3.0 g gain over 72 hours on a 0.445 sq ft test area is 4.96 lb, nearly 2 lb over a 3 lb limit; the same gain over 60 hours would read 5.95 lb, which is why the standard fixes a 60 to 72 hour window and the start time is written down. Enter the test area your kit states. It also counts the tests the standard asks for: three in the first 1,000 sq ft and one per further 1,000 sq ft, so five for 2,400 sq ft. The limit is the flooring or adhesive manufacturer's, and many now require the ASTM F2170 relative humidity probe instead.
Formula or tableMVER = 24,000 x mass gain (g) / (453.592 x test area (sq ft) x hours), lb of water per 1,000 sq ft per 24 h; passes when MVER <= the manufacturer's limit; tests = 3 for the first 1,000 sq ft + ceil((area - 1,000) / 1,000).
Source and editionASTM F1869, Standard Test Method for Measuring Moisture Vapor Emission Rate of Concrete Subfloor Using Anhydrous Calcium Chloride, by name; the edition was not read here (ASTM sells it), and the arithmetic is its unit conversion with 453.592 g per lb.
Free accessASTM F1869 is sold by ASTM; the conversion is grams to pounds, the test area to 1,000 sq ft, and hours to a day.
What governsEstimate. AHJ and licensed professional govern.
API field namesmass_gain_g, test_area_sqft, hours, limit_lb, floor_area_sqft, mver_lb, margin_lb, tests_required
- Test area as the kit states it dome inside area or net exposed area, whichever the kit's instructions givekit instructions
- Grams per pound 453.592unit definition