[Current trends in improving the accuracy of indicator tubes]

The accuracy of the determinations made by the indicator tubes is constantly improved by the introduction of accurate dosage apparatuses for their calibration and due to the methods and criteria for the control of their quality. Modern dosage apparatuses for calibration were designed at RIHOD, reading the effect of air humidity and some other obstructive substances. A mathematical model was obtained, via a statistical way, of air humidity effect on the indices of some kinds indicator tubes for chlorine, hydrogen chloride, sulphur dioxide, etc. Correction coefficients were introduced reading air humidity effect, in this way guaranteeing the error of the determination not to exceed the allowable error, internationally accepted, of +/- 25%. In fact, the results obtained for the error were between 8 and 15% within the whole range of air relative humidities. With the accuracy attained some indicator tubes compete with the classical and apparatus methods for sanitary-chemical control of the air in the working environment.