The sensory pollution load and microbial contamination of glass-fibre filters at high and low relative humidity were investigated in an experimental set-up in the laboratory. Dust and particles from the outdoor air were collected in two EU7 glass-fibre filters for a pre-conditioning period of 16-18 weeks during which there was a constant airflow with a velocity of 1.9 m/s through the filters. One of the filters was exposed to outdoor air of approximately 40% relative humidity and 10°C, the other to outdoor air of approximately 80% relative humidity and S0 C.

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:

An ASHRAE special publication can help designers minimize the number and severity of HVAC system noise and vibration problems.

Is fighting sound with sound the future for noise control? James Macneil hears how active noise technology is slowly being fine-tuned for commercial use.

Designing for grille and diffuser noise is of paramount importance. Neil Jarman looks at the data currently provided by manufacturers and provides some design tips.

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.

To evaluate the health risk posed by particles emitted from sound absorbent materials used in ventilation channels, the number, size, shape and composition of fibers and other particles must be characterized. A method of studying those particle characteristics has been developed. The number concentration of small particles in the testing chamber was measured with a condensation nucleus counter. Both scanning electron microscopical and optical microscopical analyses were possible for filter samples because of the low particle concentration of background particles in the testing chamber.

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.