Controlled Test Case: Unoccupied Room with Dry Ice CO₂ Source

Purpose:

To measure the effect of opening a door and window, along with use of box fans, to enhance outdoor air ventilation in an under ventilated room. The controlled test case uses dry ice to elevate the room CO₂ level.

When outside air is added to a room with elevated CO₂, the CO₂ is diluted and the concentration drops. The rate at which the concentration drops can be used to calculate the number of outside air exchanges per hour (ACH).

Materials & Methods:

A conference room at the Queen Lili'uokalani Facilities Campus (QLFC) was used to test the effectiveness of box fans for enhancing ventilation. The layout of the test facility is shown below. Lasko 20" box fans were used for circulating within and exhausting air out of the room. An Aranet4 CO₂ sensor was used to measure CO₂ levels. Dry ice was used to elevate the unoccupied conference room CO₂ levels. ACH was calculated using the equation provided by the 5-Step Guide and a Google Sheets spreadsheet.

At the start of the experiment, the outside (ambient) CO₂ level was 415 ppm. Following instructions in the 5-Step Guide, a cooler containing 10 lbs of dry ice was placed on the conference room table and opened. Sublimation of CO₂ from the dry ice was enhanced by blowing air on the blocks using a box fan. CO₂ levels were recorded automatically every minute using an Aranet4 sensor. Once CO₂ levels reached approximately 2000 ppm, the ice chest was closed and moved outside. A single door was opened to the outside and a box fan on the high setting was used to direct air out of the doorway. A second box fan was pointed tangentially away from the meeting space to circulate room air. CO₂ levels were monitored using the Aranet4 iPhone app. When CO₂ levels decreased to approximately 37% of the peak value, the experiment was terminated and the results were exported from the Aranet4 device to a .csv file. The equation provided in the 5-Step Guide was used to calculate ACH.

In Scenario #1, we tested the effect of using a box fan in combination with opening a single standard size door.

In Scenario #2, we tested the effect of opening a 3' x 3' louvered window in combination with the set up tested in scenario #1.