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APSD of Soft Mist Inhalers (SMIs)

For SMIs as for nebulisers, the evaporation of droplets exacerbated by the thermal mass of the impactor can be a problem. Loss of solvent reduces droplet size, producing artificially low APSD measurements, compromising the integrity of the resulting data. Cooling the impactor to approximately 5°C is the recommended method for overcoming this problem. Classified as active devices, the recommended flow rate for ADI testing is 28.3 L/min for the ACI or 30 L/min for the NGI.