When do you know your ventilation ductwork needs cleaning, how do you go about it and what does hygienic mean? A new set of practical guides .. looks at addressing these issues.

More than three-fifths of the households in the U.S. heat or cool their homes with ducted forced air systems, so chances are good that air ducts are lurking within your walls, floors, or ceilings. These air ducts move conditioned air to warm and cool your family. They can be a great source of comfort-but more likely they are wasting energy and costing you money. Typical duct systems lose 25 to 40 percent of the heating or cooling energy put out by the central furnace, heat pump, or air conditioner.

Nosocomial infectior1s are a major problem in many hospital buildings, with ,approximately 10% of patients acquiring such an infection during a hospital stay. Airborne transmission is one of the important routes for a number of nosocomial pathogens. To combat this proq,lem there are a number of engineering control strategies, such as the use of ultraviolet germicidal irradiation and advanced ventilation techniques, which can be used. This paper outlines the 'state of the art' in air disinfection, and reviews recent research work in this field.

Ultraviolet light has been demonstrated to effectively de-activate pathogens and all other airborne bacteria, virus and mould species. The technology is already widely used within process users of air, GMP manufacturers and by those with an interest in a high quality indoor air supplies, such as call centres, banks and other high employee density locations. The technology is now being applied to reduce the incidence of nosocomial infection at healthcare providers worldwide.

Buildings located in noisy areas require a high degree of sound insulation. This will usually involve making the building envelope virtually airtight, and as a result losing the possibility of utilising natural ventilation. The solution is to employ a mechanical ventilation system, but such systems can themselves constitute a source of intrusive noise. Discontinuities in ducts result in the generation of flow noise and a loss of static pressure. The greater the discontinuity, the greater is the loss in static pressure and the greater is the sound power generated.

Perceived air quality, symptoms, and perception of the environment were studied in a naturally ventilated office building in which a felt carpet was substituted by linoleum on the first floor and by polyolefine floor tiles, known from previous studies to be a low-polluting floor material on the second floor, while the felt carpet remained unchanged on the ground floor. A panel of 36 untrained subjects occupied the offices on each storey for a period of one hour in a balanced design on a day when normal occupants were absent.