Sick building syndrome--know your ventilation rates.

To summarise, although the occurrence of sick building syndrome could be due to a range of causal factors, research shows that it is probable that low outside air intake volume and pollution generated by the ventilation system and the building contents play a role in producing its effects. This being so, it is important that the flow of outside air into the building and the distribution of fresh or mixed air around the interior are known and controlled. However it is difficult to control the flow rate by conventional means and the use of fixed minimum position dampers is not likely to maintain a minimum fresh air flow rate under most wind velocities. What is needed is a control system which relies on direct measurement of air flow rate connected to a modulated minimum outside air intake damper to provide a constant and verifiable volume of fresh air flow. Flow sensors also open up the possibility of direct measurement and control of return and mixed air volumes and of course the flow of air anywhere else in the system.