SPIGOT SELECTION Published noise data for Square and Slot Diffusers is for the device with dampers in the fully open position. Care must be taken to ensure that the noise generated at the spigot entry does not exceed that level. The following table gives the maximum volume in m3/sec. that each spigot size can handle for a given noise criteria. Spigot Diameter NC25 NC30 NC35 NC40 125 0.031 0.037 0.043 0.055 150 0.044 0.053 0.062 0.080 200 0.079 0.094 0.110 0.141 250 0.123 0.147 0.172 0.221 300 0.177 0.212 0.247 0.318 350 0.241 0.289 0.337 0.433 400 0.314 0.377 0.440 0.565 450 0.398 0.477 0.557 0.716 Note For ideal air distribution to the supply diffuser a straight run of ducting equivalent to 3 x the neck dia. of the diffuser is required.