5.1 This test method is a standard procedure for determining the resistance to water penetration during rapid cyclic pulses of dynamic air pressure differences. The air-pressure differences acting across a building envelope vary greatly. These factors should be fully considered prior to specifying the test pressure difference to be used.

5.2 The median test pressure used in this test method is defined as the specified test pressure supplied by the user and related to the maximum positive building design pressure. This test method departs from the format of other ASTM water penetration resistance test methods based on a maximum test pressure related to a maximum positive building design pressure.

5.3 As the specified or median test pressure is increased, the maximum test pressure in this procedure is also increased to 1.5 times the specification median test pressure. This higher maximum test pressure may not be representative of actual building service conditions. For this reason the maximum recommended median test pressure is 480 Pa (10 psf), which corresponds to a maximum test pressure of 720 Pa (15 psf).

5.4 The pulsed pressure of this test method may act to pump water past dry seals and breather systems of units incorporating these features, thereby making the test method more severe than a static pressure test method. On the other hand, the low pressure portions of the pressure cycles of this test method may allow weep systems and drainage dams to dissipate water from units incorporating these features, thereby making the test method less severe than a static pressure test method.

Note 1: In applying the results of tests by this test method, note that the performance of a wall or its components, or both, may be a function of proper installation and adjustment. In service, the performance will also depend on the rigidity of supporting construction and on the resistance of components to deterioration by various causes, (vibration, thermal expansion and contraction, and so forth). It is difficult to accurately simulate the actual complex wetting conditions that can be encountered in service, with large wind-blown water drops, increasing water drop impact pressures with increasing wind velocity and lateral or upward moving air and water. Some designs are more sensitive than others to this upward moving water.

Note 2: This test does not identify unobservable liquid water which may penetrate into the test specimen.