THE SPATIAL DISTRIBUTION

The Spatial Distribution of Carbon Dioxide in an Environmental Test Chamber

ABSTRACT

The spatial distribution of CO2 level in a classroom carried out in previous field work research has demonstrated that there is some evidence of variations in CO2 concentration in a classroom space. Significant fluctuations in CO2 concentration were found at different sampling points depending on the ventilation methods and environmental conditions prevailing in individual classrooms. However? how these variations are affected by the emitting sources and the room air movement remains unknown. Because the classrooms studied were large and ventilated differently? it was difficult to explain the causes of the variation in the CO2 distribution. Hence? it was concluded that detailed investigation of the CO2 distribution need to be performed on a smaller scale. As a result? it was decided to use an environmental chamber with no ventilation and mechanical ventilation for the same internal temperature and heat loads? to study the effect of air movement and ventilation method on the distribution of CO2 concentration in a room. The role of human exhalation and its interaction with the plume induced by the body's convective flow and room air movement due to different ventilation methods were studied in a chamber at the University of Reading. These phenomena are considered to be important in understanding and predicting the flow patterns in a space and how these impact on the distribution of contaminants. This paper attempts to study the CO2 dispersion and distribution at the exhalation zone of two people sitting in a chamber as well as other locations in the chamber. The horizontal and vertical distributions of CO2 were sampled at locations with a probability that CO2 variation is considered high. One of the most acutely toxic indoor air contaminants is carbon monoxide (CO)? a colorless? odorless gas that is a byproduct of incomplete combustion of fossil fuels. Common sources of carbon monoxide are tobacco smoke? space heaters using fossil fuels? defective central heating furnaces and automobile exhaust. Improvements in indoor levels of CO are systematically improving from increasing numbers of smoke-free restaurants and other legislated non-smoking buildings. By depriving the brain of oxygen? high levels of carbon monoxide can lead to nausea? unconsciousness and death. According to the American Conference of Governmental Industrial Hygienists (ACGIH)? the time-weighted average (TWA) limit for carbon monoxide (630-08-0) is 25 ppm.

Keywords: Air Quality; Carbon Dioxide; Spatial Distribution; Ventilation Methods

The Spatial Distribution of Carbon Dioxide in an Environmental Test Chamber

1. Introduction

The use of Carbon Dioxide (CO2) as an indicator of indoor air quality (IAQ) and as a tracer gas to estimate air exchange rates in buildings is widely applied by many researchers nowadays. Although it is present in the atmosphere? CO2 gas that is generated by room occupants or released from cylinders is sometimes used as a tracer gas in ventilation research due to its low cost and safety consideration.

It has been known for decades that the concentration of carbon dioxide in the atmosphere has been increasing due to burning of fossil fuels and ...