Field tests and a model allowed to study contaminant concentrations in a single family home in California operating with natural ventilation or with one of six mechanical ventilation systems (cyclic or continuous, multi-point or single-point exhaust). Continuous ventilation appears to be better for contaminant levels control.
Ventilation airflow rates and internal air distribution were measured in four poultry slaughter plants (250 to 775 workers), equipped with negative pressure ventilation systems (exhaust flow rate from 7.1 to 27.4 m3/s - no air intakes - supply air entering through various openings). Results lead the authors to recommend the installation of diffusers for makeup air supply, changes in the organisation of rooms to avoid contamination of one by the other and regular maintenance and cleaning of ventilation components.
This was a study of the relationship between mechanical ventilation and sick business syndrome in an office building with 1250 employees, where workers blamed the mechanical ventilation and indoor air quality for causing typical SBS symptoms such as nasal, eye, skin and mucous membrane irritations, lethargy and headaches). The building's mechanical ventilation rates were high.
A dynamic computer program was used to analyse the operation and performance of a thermal comfort controller for HVAC systems with forced-air ventilators. The software tool used was GEMS (Generalized Engineering Modeling and Simulation). Simulations indicated that when using a conventional thermostat, any form of mechanical ventilation is likely to increase the moisture content of the air inside a conditioned space in a cooing-dominated hot and humid climate. States that mechanical ventilators in this situation may contribute to indoor air quality problems of high moisture levels.
The study investigates the effect of mechanical ventilation and high-efficiency vacuuming on house dust mite numbers and allergen concentrations in dwellings of mite-sensitive asthmatics. Of forty houses, some received mechanical ventilation, some an HEVC, and some both, while a number acted as controls. The monitoring exercise lasted for twelve months. It was found that humidity was reduced in homes with mechanical ventilation and mite numbers reduced accordingly. Use of the vacuum cleaners enhanced the effect.
A move to mechanically ventilated low-dust mite affected, 'healthy' homes was investigated in relation to asthma control. Fourteen patients, allergic to dust mite allergens, were studied. Clinical improvements were significant in the patients, in contrast to the control patients. The study found a significant relation between reduction in medicine score and the fall in house dust mite exposure.
Thirty asthmatic patients were tested for exposure to house dust mites before and after moving to mechanically ventilated homes. There was found to be a significant reduction in house dust mite numbers after four months in contrast to the control group of 23 patients. A further reduction had occurred after 15 months. Air change rates increased from 0.40 ACH to 1.52 ACH. There was also a reduction in absolute air humidity.
Documents a study of airborne fungal concentration in a newly constructed building on the Gulf coast. States that fungal concentrations indoors were consistently below those outdoors, and samples did not clearly indicate contamination in the building, although visible growth was evident in the ventilation system. Concludes that the intrusion of most of the outdoor fungal aerosol is prevented by modern mechanically ventilated buildings, and that even extensive air sampling may not give the whole picture.
Examines the effect of a new, individually controlled ventilation system on employee symptoms. Two groups of employees were studied in one office building with mechanical ventilation, with one group the control. Individual control of the workspace ventilation was given to the intervention group. The new system gave higher air velocities, more variable temperatures, and higher concentration of airborne dust and fungal spores. Nevertheless, after four months, employees reported fewer symptoms.
Describes a study carried out in order to examine the relationships between the ventilation rate and the type of ventilation system on one hand, and objective nasal measures on the other. The method was to carry out a standardised investigation which included acoustic rhinometry and nasal lavage at a school. 279 persons at 12 primary schools in Sweden were invited and 84% participated.