How can one tell when the spirometer needs to be re-calibrated ?
There should be no more than 10% variation between the PEF readings shown on the digital display and the mechanical scale. If a greater difference develops, then the device should be cleaned. If it continues to read incorrectly, re calibration by experienced technicians is required (in the UK, Clement Clarke free for the first 12 months, thereafter 25 plus P&P).
