Internal Contaminant Source Dilution and Filtration in Dedicated Outdoor Air Systems

Heating, ventilation and air-conditioning (HVAC) systems account for more the 50% of energy use in residential buildings [1] and approximately three-quarter in healthcare environments [2]. Hence, HVAC systems are a favorable sector for sustainability with a great potential of energy savings. The engineering approach to this issue has led to the advent of newer and more sustainable technologies. Dedicated outdoor air systems (DOAS) are a case in point. By decoupling the sensible and latent loads, an enormous saving can be achieved in the amount of air to be conditioned. Ventilation systems are designed to satisfy three predominant requirements: (1) to deliver fresh air to occupants and dilute the indoor generated contaminants, (2) to control the temperature and humidity in indoor spaces, and (3) to pressurize the space. There is ample evidence that the DOAS facilitates the last two requirements with more quality and less cost, which makes it more sustainable. This work, however, focused on the effect of using this system on the first requirement, particularly with regard to the indoor generated contaminants. The results showed that compared to the traditional ventilation systems, the DOAS system less effectively treats the indoor generated contaminants. Therefore, other mechanisms such as filtration must be properly implemented to limit the contaminants level below their standard threshold.