The FT 3000 is activated. The negative pressure that exits will cause air leakage in the mask. Mask leakage is determined as a direct function of pump speed. Leakage is directly related to the respirator fit. The lower the leakage, the better the fit.
Leak rate is reported in cubic centimeters per minute.
If a satisfactory fit is not achieved by the quantitative test procedure as described above, another size or model respirator should be selected and the test repeated. Either a positive or negative pressure test for tightness of fit must be applied each time a respirator is used. Positive Pressure Test a. Close off the exhalation valve with the palm of the hand. Exhale gently into the facepiece. The face fit is considered satisfactory if slight positive pressure can be built up inside the facepiece without any evidence of outward leakage.