Abstract
Carbon dioxide (CO2) is an indicator of indoor air quality. Ventilation based on the use of a CO2 indicator helps to prevent people from acquiring many diseases, especially respiratory viral infections. Therefore, the monitoring of CO2 is a pivotal issue in the control of indoor air quality. A nondispersive infrared (NDIR) analyzer with a wide range of measurements (i.e., ppmv to percentage levels) was developed for measuring carbon dioxide (CO2) in an indoor environment. The effects of optical pathlength and interfering gases were investigated. The pathlengths of the analyzer were varied at 4.8, 8, 10.4 and 16 m, and the interference gases were CO; NO2; SO2; H2O; BTEX (i.e., benzene, toluene, ethylbenzene and m-/p-xylene) and formaldehyde. The lower detection limit, selectivity and sensitivity were determined to evaluate the performance of the analyzer. It was found that different pathlengths should be used to produce linear calibration curves for CO2 from ppmv to percentage levels. As a result, a wide-range NDIR analyzer, coupled with flexible pathlengths from 4.8 to 10.4 m, was developed. In terms of interference, only H2O should be taken into account due to its high concentration in indoor air. CO should be considered in some special locations at the ppmv level. The measurement errors for ppmv and the percentage levels were 0.4 and 0.9%, respectively.
Highlights
Besides being a greenhouse gas in the atmosphere, carbon dioxide (CO2 ) plays an important role in indoor environments [1,2,3,4,5,6,7]
It can function as a fire alarm indicator for the indoor environment in which it is present at high concentrations [1,2,3,5]
Ventilation has been reported as one of the primary methods used to reduce the rate of infection of the virus in indoor environments, which may result in a decline in the overall infection rate due to the fact that people spend most of the time in buildings [19]
Summary
Besides being a greenhouse gas in the atmosphere, carbon dioxide (CO2 ) plays an important role in indoor environments [1,2,3,4,5,6,7]. A CRDS analyzer includes a laser source, highly reflective mirrors and a detector It measures the changes in the decay rate of light. CO2for or measuring the gas in cases that do not require a an analyzer [33] To increase the lower detection limit of the analyzer, the concentration of the target gas and the optical pathlength. Was reported that the sensitivity improved approximately measure the accumulated concentration, leads to an increase in the cost of the analyzer and associated times [36,37]. White cell consists of three concave mirrors that have the same radius cells have been widely used to produce a multi-pathway gas cell for the NDIR analyzer. This study was conducted to develop a wide-range CO2 NDIR analyzer with high accuracy. CO2 NDIR analyzer were investigated to help to improve the accuracy of the analyzer
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