The quantitative determination of differential pressure and airflow for proper room pressurization is an HVAC design area that has not yet developed a standard rule.In this article current design guidelines and field practices for room pressurization are investigated. Practical field tests were performed in two types of facilities: a tuberculosis research lab and a cell transplant unit.

The excitation of pulsed plasmas for the air treatment (odors, toxic and volatile gases suppression, and sterilization) needs fast high electric pulse generators with powers that can require high repetition frequencies according to the applications .This paper shows that those solid state generators are today available. They use several technologies thanks to a global approach of the high power electronics physics and recent evolutions of active and passive components.

The heterogeneous photocatalysis relies on the activation of a half-conductor. The most often used is TiO2, with radiations of energy at least equal to the ones of the width of the forbidden band.The electronic changes due to that activation lead, in the presence of air, to the creation of oxygenated radicals. Those radicals attack the adsorbed organic compounds and degrade them. Starting from evaluations made with a laboratory photoreactor, this paper shows that photocatalysis is an appropriate method to purify air in domestic buildings (or other confined spaces).

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.