Convergence of measurement results during special assessment of labor conditions is one of the key indicators determining the quality of measurements. The field work of specialists performing direct tests differs significantly from laboratory conditions. To improve the culture of testing, in-laboratory comparison tests are carried out, the results of which are used to carry out corrective actions according to ISO 9001, to improve the quality of laboratory work and to improve the accuracy of the results of special assessment of working conditions within the framework of confirmation of the competence of the laboratory. To determine the dustiness of the bricklayer’s workplace the weight method was used, which consists in collecting dust on filters with subsequent weighing and concentration determination. The quality assessment of in-laboratory tests was performed according to the conditions of reproducibility. Field tests were carried out to determine the dustiness of the working place of the bricklayer at the construction site. The single maximum permissible dust concentration of 1.67 times was detected at the bricklayer’s workplace. The average concentration of dust on the studied worker in the air was 10.00 mg/m3, the convergence of the results obtained r = 22.0%. In the course of the study the maximum permissible discrepancies between the results of two tests were established, which allows formalizing the criteria of data acceptability within the framework of special labor assessment.