What is the accuracy of the QRS Orbit Portable Spirometer?

Flow: FEF 25-75: ±5% of indication or ±200 ml/sec, whichever is greater. PEF: ±10% of indication or ±300 ml/sec, whichever is greater.
Volume: FVC and FEV1: ±3% of indication or ±50 ml/sec, whichever is greater. MVV: ±10% of indication or ±15 L/min, whichever is greater.