The slew rate of the smoke density in the EN54 test duct typically is set to be about 0.06 dB/m min. An example of 3 paraffin oil measurements in the EN54 test duct is shown in Fig. 12(a). The achieved linearity is a precondition for performing dust tests in a similar manner as smoke tests according to EN54. The increase of the dust concentration could be within the following limits