CO₂ MEASUREMENTS FOR UNCONVENTIONAL MANAGEMENT OF INDOOR AIR QUALITY

Abstract

Carbon dioxide (CO2) is a known global pollutant and is responsible for the global warming that the planet has been experiencing for the last few decades. On a local scale, outdoor CO2 does not pose any risk for the environment and humans. Risks are usually far from involving human beings in the majority of indoor environments, although high CO2 concentrations may entail temporary adverse effects that are similar to the typical symptoms of the so-called "sick-building syndrome". Such effects become even more important on workplaces or at school/university, since high CO2 levels may negatively influence the productivity and the learning capability of individuals. To understand the magnitude of the problem, a monitoring campaign was carried out in four classrooms and in a library of a university in northern Italy. Three of the classrooms under observation were not equipped with an air extraction system. The CO2 concentration was monitored with low-cost non-dispersive infrared digital sensors in two periods of the year: between February and March and at the end of May. During those periods, the number of occupants, temperature and relative humidity were also monitored, as well as any opening of the windows (where available). The results showed that, where automatic air extraction is not available, CO2 concentrations can exceed 5,000 ppm. In general, the lower the ratio between the room volume and the number of occupants, the higher the concentrations achieved. The installation of lowcost sensors might prove useful to prevent the negative effects from the exposure to high CO2 levels and help achieve more sustainable conditions in indoor spaces, since the sensors could inform lecturers and students on the need for opening doors and/or windows when air extraction is not provided.

Optimal Hybrid Ventilation Strategy to Assure Adequate Indoor Thermal Comfort and Air Quality in Educational Spaces under a Tropical Climate

“…As mentioned by [12], opening windows can increase airflow in classrooms and decrease the indoor concentration of CO2. A "TOWD" was proposed keeping the HVAC system on.…”

“…Also, these scenarios were simulated with no occupancy for 20 minutes and for 1 hour at 11:00 (Oc 0 x 1h @ 11), which was the time identified as the first hour during the days in which it exceeded 1000 ppm. It is decided to vary the occupancy because there is evidence in the literature that the concentration of CO2 depends on the occupancy indoors [9][10][11][12]. Another scenario proposed was Night Purging "NP" (full opening of doors and windows in periods where there is no occupancy) combined with occupancy variation during the day.…”

Review of Parameters Measured to Characterize Classrooms’ Indoor Environmental Quality

“…CO 2 is a marker of ventilation adequacy in the presence of people indoors and is the most prevalently measured parameter in connection with IAQ monitoring [117]. CO 2 was measured mainly with a non-dispersive infrared (NDIR) sensor.…”

Planning Sustainability in Higher Education: Three Case Studies

“…The first subsector (4.1 "Indoor air quality") was created as a response to the relatively high concentrations of carbon dioxide (CO2) in indoor air. Although in classrooms/offices CO 2 concentrations are not critical for human health, symptoms similar to the so-called "sick-building syndrome" may occur [22], [23]. To reduce the CO 2 concentrations within acceptable levels, the Plan aims at mapping structural and installation issues that may negatively affect indoor air quality, monitoring indoor air quality to highlight possible criticalities, and developing guidelines to manage indoor air.…”