Traditional air-handling unit (AHU) control systems link the position of the exhaust air damper, recirculation air damper, and outdoor air damper. Tests at the National Institute of Standards and Technology (NIST) on a variable-air-volume (VAV) AHU have shown that air can enter the AHU through the exhaust air damper. This can negatively impact indoor air quality if the exhaust air duct is located near a pollution source. This paper presents a new control system for variable air volume AHU's that use volume matching to control the return fan.
The comparison of the performances of ventilation systems must take into account different issues. For indoor air quality, different kinds of pollutant sources have to be defined. To make an evaluation of the results, the best approach is to consider the people exposure. Four generic pollutants are taken into account : rooms components or furniture, human metabolism, cooking activities, passive smoking. As the definition of the unit for each pollutant is free, it is useful for their comparison to press them on a common "normalised" basis.
The paper will discuss problems connected with incorporation of stochastic factors into deterministic models of indoor air quality. Three different methods: a quasi dynamic multi-zone modelling with generating of input data time series, multi-zone modelling based on the theory of stochastic differential equations, Monte-Carlo simulation with independent random generating of stochastic parameters, will be shortly presented. Described methods are compared on the base of computer simulation of CO2 concentration in simple two compartment office.
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