Current approach for design and installation of mechanical ventilation systems in houses is described in the framework of Canadian building codes and standards, which contain requirements about air change rates, air distribution, sound level, interference with other systems or building envelope.
Gravimetric determination and continuous monitoring of respirable dust in air has revealed that there are high levels of dust at some roadside and indoor locations in urban areas. Furthermore, where high dust levels are measured in roadside samples, high concentrations are also measured in adjacent buildings. The dust levels measured inside a building have been shown to be very closely correlated to ambient levels, and traffic emissions, particularly from diesel vehicles, are the principal source of respirable particulates.
In 1987, workers in the kitchen of one of the teaching hospitals in Halifax, Nova Scotia began to experience symptoms of pruritus, folliculitis, wheezing, conjunctiva/ irritation, sore throat and headache, all suggestive of an indoor air quality (IAQ) problem. Approximately 127 of 160 kitchen workers were affected over a 2-year period and the complaints included cognitive difficulties and reactivity to environmental irritants.
When outdoor air is the main source of pollutants indoors, mechanical air ventilation can be viewed as having two fronts of action in controlling indoor air quality. The first is its capacity to remove indoor air pollutants by dilution, and the second is its capability to prevent, through its pressurisation effect, the pollutant source (i.e. untreated outdoor air) from infiltrating, through the building envelope, to the occupied space.
Acceptability of clean air and air polluted by building materials was studied in climate chambers with different levels of air temperature and humidity in the ranges 18-28°C and 30- 70% relative humidity (RH). The acceptability of the air quality immediately after entering a chamber and during the following 20-min whole-body exposure was assessed by 36 untrained subjects who maintained thermal neutrality by modifying their clothing.
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