This article describes bacteria and viruses usually considered as candidates for biological weapons. It also presents chemical agents that might be used as chemical weapons. It shows how HVAC systems can be designed with safeguards to protect against entry and/or circulation of these agents. It explains how air filtration can provide an additional defense, using HEPA filters, activated carbon filters, antimicrobial treated filters, ultraviolet light emitters or electrostatic air cleaners with UV emitters.

This article describes the various types of fungi (yeasts, molds, mushrooms, ...). It reminds that they are single or multi-cellular non-motile organisms which rely on other organism or environment for nutrients. Fungi can generate spores which can germinate under appropriate conditions (moisture, substrate, temperature) after an extended period during which they remain dormant.

The article presents the advantages of decoupling the outdoor ventilation air cooling and dehumidification from the space cooling and dehumidification. These dual-path systems (one air handling unit for outdoor air with total energy recovery, another air handling unit for the recirculation air, and a single air supply delivery system) are used in all-air variable air volume system designs. They can be combined with CO2-based demand controlled ventilation, which offers superior control and cost savings.

This paper presents a survey on methods of measuring airflow, especially methods using inlet nozzles. Methods are compared with respect to uncertainties due to nozzle shape and/or measurement, handling friendliness, and economics. Authors describe a new nozzle contour with a constant air velocity along its surface. They explain advantages and disadvantages of this new design.

Pressure loss coefficients were measured for several flat oval tee and lateral fittings. The paper gives measurement results and pressure loss curves.

This paper presents the results of 23 experiments during which reinforced spiral ducts were submitted to underpressure until they collapse. Experiments were operated with different duct diameters, reinforcement spacing, material and duct thickness. Results were analyzed and led to an equation for estimating the collapse pressure of such ducts.

A model for air flow inside ducts with leakages has been established from the equations governing the variation of total pressure and velocity along the duct. It was found that duct performance could be expressed as a function of two dimensionless constants, allowing the calculation of the required total pressure and velocity in the duct.

From experimental data on eight common air diffusers, authors developed simplified methods (the box method and the momentum method) to describe air flow and temperatures in the air jet that can be used as imput data for room air flow CFD calculations. The box method is appropriate for most of the diffusers. The momentum method gives good results for five diffusers. As it is simpler, authors recommend that it is used whenever applicable.

This study aims to validate a CFD model (Flovent) for calculation of temperature and particulate concentration in a ventilated room. Measurements were operated in a test room with a heat source and a cigarette source. Good agreement was found with the model for temperatures with a mixed ventilation system in the room as well as with a displacement ventilation system. For particulate concentrations, the model was validated for mixed ventilation and 'borderline validated' with displacement ventilation.

A simplified model for room cross-ventilation airflow has been developed using scaling analysis,experimental correlations and computational fluid dynamics. The model considers the main jet region and the recirculations region and leads to a set of formulas that predict the airflow rates and characteristic velocities in these two regions. Examples of application of the model to cross-ventilation design are presented.