The disintegration of dry powder agglomerates into their primary constituents is desirable for particle sizing characterisation and therapeutic drug delivery. A basic understanding of the time dependant emitted dose patterns from dry powder inhalers (DPIs) is largely unknown despite their wide usage. Through laser diffraction particle sizing analysis, we have demonstrated that the majority of the aerosol cloud is released before the peak inspiration flow rate (PIFR) has been achieved and therefore, the early part of the inspiratory maneuver could be a critical determinant in the quantity of the powder emitted. When inhaling through the low resistance RS01® DPI (Plastiape, Osnago-Lecco, Italy). It is likely that all the powder is drawn from the device in the first 30-120 ms after actuation. Aerosol concentrations were recorded as a function of time to provide an understanding of the powder emptying rate from the RS01® at different flow rates 30, 60 and 90 L/min. Peak aerosol concentrations were achieved more rapidly at higher flow rates over shorter time durations. This fast laser diffraction approach is proposed to be a powerful development tool in the analysis of DPI performance.