This International Standard specifies requirements for peak expiratory flow meters (PEFMs) intended for the assessment of pulmonary function in spontaneously breathing humans. This International Standard covers all devices that measure peak expiratory flowrate in spontaneously breathing humans either as part of an integrated lung function device or as a stand-alone device. Planning and design of products applying to this International Standard should consider the environmental impact from the product during its life cycle. Environmental aspects are addressed in Annex E. NOTE Additional aspects of environmental impact are addressed in ISO 14971.