Method of correcting componential concentration in expiration and expiration analyzer

An expiration analyzer comprising:

• a first sample measuring passage means, having a sample gas measurer which measures at least one or two components in expiration, for receiving from a collection port an expiration sample of alveolar air being mixed with at least one of air from a dead space and ambient air;
• a second sample measuring passage means, having a standard gas measurer which measures at least one of O.sub.2 gas and CO.sub.2 gas as standard gas and being provided in parallel with said first sample measuring passage means, for receiving from said collection port said expiration sample being identical to that guided in said first sample measuring passage means;
• a heating means for heating passages between said collection port and said sample and standard gas measurers;
• and
• a computing means for correcting a componential measured value in said expiration sample, being measured by said sample gas measurer, by a measured value of said standard gas concentration in said expiration sample, being measured by said standard gas measurer, with reference to concentration of a standard gas in end-tidal air.