Abstract

Since most people spend about 90 percent of their time indoors, having good indoor air quality plays a significant role in human health. Based on EPA studies, indoor air pollution is among the top five environmental health risks. Ozone is considered as one of the typical indoor air contaminants. Air cleaners are one of the indoor sources of ozone production applied for the deodorization and disinfection of air and other indoor sources that release ozone, including printers and photocopiers. Therefore, reliable detection of ozone, especially in low concentrations using sensitive and accurate ozone monitoring technologies, is very noticeable and its market demand is on the rise. However, these detecting technologies suffer from positive or negative interferences from other chemical compounds which exist in the desired environment. Also, humidity and temperature changes can affect indoor ozone levels and ozone monitoring technologies performance.
In this research, different environmental physical parameters effects like air velocity, airflow direction, and humidity on the performance of ozone monitoring technologies were evaluated in a full duct and small-scale environmental chamber. Also, we examined the responses of these monitoring instruments in the presence of some interfering compounds, including Acetone, Toluene, and Ethanol, using a small-scale chamber at 50% RH and dry condition (0.01%).
The results demonstrated that different airflow rates and airflow directions had a negligible effect on the UV sensors response. While electrochemical and metal oxide sensors outputs were remarkably overestimated with increasing airflow rate. This increase was more evident for electrochemical and metal oxide sensors when placed perpendicular and parallel to the airflow, respectively. Furthermore, the responses of 211-2B, Teledyne, POM and BW experienced a positive interference with rapid humidity variations from 30% to about 80% and a negative bias from 80% to 30% RH. In contrast, BW Solo behaved oppositely. It was difficult to follow the metal oxide changing trend with humidity variations because of the instrument time interval (minimum 10 min). In the absence of ozone, Ethanol caused a slight negative interference to the 211-2B sensor in humid (50%) and dry air (0.01%) and a significant negative bias to Teledyne at 50% RH. 211-2B sensor did not respond to acetone at 50% RH, but it experienced a positive bias in dry air. A considerable positive interference was observed in Teledyne reading at 50% RH. Toluene led to a slight positive interference in 211-2B response in humid and dry conditions. BW Solo and ECO Sensor in the presence of these VOC compounds were consistently showing zero concentration.