This study has the objective of applying the "age of air" concept and tracer gas techniques in the evaluation of ventilation characteristics of workplaces equipped with a general ventilation system. A Class I OK cleanroom was selected for this study and C02 was used as a tracer gas. After the tracer gas was released in the form of a pulse into the cleanroom, its concentration was measured as a function of time at various locations by non-dispersive infrared photometers. The average age of air at each location was then calculated from the C02 concentration data.
As active noise control systems begin to penetrate the market place, are the days of the passive attenuator numbered? Andrew Brister looks at the likely future for anti-noise.
The issue of sound quality in offices and other occupied spaces has been of continuing interest since the 1950s. Existing assessment methods do not adequately account for the Low-frequency background sound ( < 250 Hz) produced by operating heating, ventilating, and air-conditioning (HVAC) systems, in particular, Low-frequency rumble. This paper discusses the results of ASHRAE-sponsored research in which more than 75 HVAC noise samples were collected, normalized, and categorized in terms of sound quality.
Fans and their associated ventilation ducts are amongst the major sources of airborne noise encountered within a submarine. Health & Safety Standards require that the ship's crew are not exposed to unnecessary high levels of noise and have a suitable environment free from intrusive noise in order to work and rest. The problem with noise emitted from fans and ducts in submarines can be categorised as follows:
HVAC system designs must address both high indoor air quality as well as energy efficiency as the awareness of and demand for proper air quality increases. Economic considerations such as installation and operating costs have impaired many conventional system designs to the point of compromised indoor air quality. This paper discusses many HVAC design parameters that arc critical to achieving adequate indoor air quality.
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