Measurement of air exchange rates in different indoor environments using continuous CO2 sensors

Abstract

A new air exchange rate (AER) monitoring method using continuous CO 2 sensors was developed and validated through both laboratory experiments and field studies. Controlled laboratory simulation tests were conducted in a 1-m 3 environmental chamber at different AERs (0.1-10.0 hr −1 ). AERs were determined using the decay method based on box model assumptions. Field tests were conducted in classrooms, dormitories, meeting rooms and apartments during 2-5 weekdays using CO 2 sensors coupled with data loggers. Indoor temperature, relative humidity (RH), and CO 2 concentrations were continuously monitored while outdoor parameters combined with on-site climate conditions were recorded. Statistical results indicated that good laboratory performance was achieved: duplicate precision was within 10%, and the measured AERs were 90%-120% of the real AERs. Average AERs were 1.22, 1.37, 1.10, 1.91 and 0.73 hr −1 in dormitories, air-conditioned classrooms, classrooms with an air circulation cooling system, reading rooms, and meeting rooms, respectively. In an elderly particulate matter exposure study, all the homes had AER values ranging from 0.29 to 3.46 hr −1 in fall, and 0.12 to 1.39 hr −1 in winter with a median AER of 1.15.

Indoor CO2 measurements in Serbian schools and ventilation rate calculation

“…With the assumption that inside air is well mixed, the air exchange rates are calculated on the basis of indoor and outdoor carbon-dioxide concentrations by the decay method. The time derivative for indoor concentration of air contaminant in general [16] is given by:…”

Air infiltration in Catalan dwellings and sealed rooms: An experimental study

“…Once the house had been prepared, we recorded the CO 2 concentration outside and in each room and estimated the amount of CO 2 that needed to be released in the shelter to reach the target concentration (1500 ppm). The target concentration was chosen because it is below the PEL (permissible exposure limit 8 h) as advised in the standard [10], and it falls within the concentrations reached in rooms at night as reported in other studies [12,22]. Next, 1 of the researchers entered the shelter, closed the door, manually released the calculated amount of gas from a bottle of liquefied CO 2 , using a balance to control the injected mass, and turned on a fan to mix the air and the released CO 2 until a uniform condition was achieved.…”

Indoor Air Quality and Thermal Conditions in a Primary School with a Green Roof System

“…After the end of classes when the CO2 concentrations present a maximum value, the rate of concentration reduction of the CO2 is measured [22]. The formula (2) of AER that has been proposed by [23] in general form and simplified by [24] for the case of CO2 is:…”