9 Tests for first characteristic numeralTest and acceptance conditions for the first characteristic numeral are given in Table 4.The dust test for numerals 5 and 6 shall be performed with the shaft stationary, provided that the difference in pressure between running and stationary (caused by fan effects) is lower than 2 kPa. If the pressure difference is greater than 2 kPa, the internal machine pressure during the dust test shall be depressed accordingly. Alternatively, the machine may be tested with the shaft rotating at rated speed.