Abstract
The importance of ventilation in closed workplaces increased after the onset of the COVID-19 pandemic. New methodologies for measuring the number of air changes per hour (ACH) in a premise where natural ventilation is applied are necessary. It is demonstrated how the ionic photoionization detector (PID) can be employed for tracer gas decay methodology using a volatile organic solvent (acetone). The methodology applied to calculate ACH in a naturally ventilated room, with various combinations of door and window openings, provides ACH values of between 2 and 17 h−1. Two classrooms were studied to verify if the minimum ventilation requirements recommended by official guidelines were met. The values for ACH on different days varied, mainly between 15 and 35 h−1, with some exceptional values higher than 40 h−1 on very windy days. These results agree with the quality air data recorded by the installed CO2 sensors, ensuring adequate hygienic conditions for the users of the rooms. The fast response of the PID allows the measurement of different locations in the room during the same assay, which provides additional information regarding the air distribution inside during the ventilation process. This methodology is fast and easy, and the necessary equipment is simple to obtain and use routinely, whether it is needed to measure several rooms or to monitor one room periodically.
Highlights
The ventilation of workplaces, renewing the interior air, is a necessity to maintain an environment with adequate air quality
2); and theyfor arehigh not useful compounds use future studies. This behavior is is well known in photoionization detector (PID)
The air changes per hour (ACH) values in this situation were the highest and almost triplicate the previous assay (16.2–16.7 h−1 ), but with those high ACH values, less precise results were obtained. This behavior is similar to that exposed in assay (d); door A and the window D were the zones with higher ACH values, and doors B and C were the zones with lower ACH values
Summary
The ventilation of workplaces, renewing the interior air, is a necessity to maintain an environment with adequate air quality. Its measurement is easy with specific sensors, most of them based on IR radiation absorption, but its disadvantage is its presence in the inlet gas (concentrations of around 400 ppm or higher, and not always constant depending on the quality of the outside air), which complicates calculations and may cause errors if these concentrations change over time. This can occur, especially in urban environments (traffic, heating, etc.) or if other persons are close to the measurement location. The fast response of the instrument allows the researcher to measure several locations simultaneously
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
