This International Standard specifies a method for the determination of the mass concentration of carbon monoxide present in the air at work places (or work areas) in concentrations greater than 10 mglm3 using detector tubes. Substances which, if contained in the air mass under investigation and thus in the air Sample, are known to have an effect on the instrument reading, are indicated in clause 5. Information on Performance characteristics is given in 9.2; in applications requiring better precision or freedom from interferences, the use of classical Chemical or instrumental methods is recommended (see 8519[101). The method is suitable for personal, breathing-zone sampling as well as for the general area sampling.