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Field Evaluation of CO 2 Detector Tubes for Measuring Outdoor Air Supply Rate in the Indoor Environment
Author(s) -
Norbäck Dan,
Ancker Klas,
Johanson Gunnar
Publication year - 1992
Publication title -
indoor air
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.387
H-Index - 99
eISSN - 1600-0668
pISSN - 0905-6947
DOI - 10.1111/j.1600-0668.1992.07-21.x
Subject(s) - relative humidity , carbon dioxide sensor , detector , carbon dioxide , environmental science , correlation coefficient , ventilation (architecture) , tube (container) , humidity , approximation error , analytical chemistry (journal) , mathematics , materials science , chemistry , statistics , meteorology , physics , environmental chemistry , composite material , optics , organic chemistry
Indoor carbon dioxide (CO 2 ) concentration can be used to estimate the degree of air recirculation and outdoor air supply rate. Three types of CO 2 detector tubes were evaluated by using Fourier Transform Infra‐Red (FTIR) Spectroscopy as a reference method. Two types of detector tubes (Draeger CH 30801 and Kitagawa 126 B) showed a good correlation with the reference method (r = 0.98), the 95% confidence interval of the slope being 0.89‐1.06 and 0.80‐0.95, respectively in linear regression analysis. The third type (Gastec 2LL.) showed lower correlation (r = 0.91) and a wider 95% confidence interval (0.52‐0.80) of the slope. A t CO 2 concentrations in the range 800‐1000 5 l/l(ppm), control values suggested for the indoor environment, the Draeger and the Gastec tubes underestimated the CO 2 concentration, while the Kitagawa tube showed a correct value. The difference in reading between observers was similar for all three brands of detector tubes (5‐7%), expressed as relative standard error No significant influence of the air humidity or temperature on the readings could be demonstrated. It is concluded that some brands of CO 2 detector tubes can be used to measure indoor carbon dioxide concentration with sufficient precision and accuracy. Since the relative error is relatively large at lower CO 2 concentrations, the use of such tubes for the determination of air recirculation in ventilation systems should be avoided. As a crude estimate of the outdoor air supply rate, however, CO 2 detector tubes may be used. In order to minimize the error in reading, the type of detector tube and the need for recalibration should be considered. When using CO 2 measurements as an estimate of outdoor air supply rate, the influence of age and work‐load on the individual's emission of CO 2 and the time needed to reach equilibrium, should also be taken into consideration.