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40
of dust, pollen and other contaminants often have little or no smell. These might
be seen in occasional shafts of sunlight, and become visible when they have set-
tled. Cleaning fluids such as ammonia, cigarette smoke, hair spray, deodorants
and perfumes can be most noticeable. The inflow of diesel exhaust fumes, road
tar, paint vapours and creosote creates unpleasantly noticeable pollution, even
when of short duration. The presence of harmful pollutants such as carbon
monoxide and radon gases is not detectable by the occupant.
Professor Ole Fanger has introduced units of subjective assessment for
odorants only. The olf quantifies the concentration of odorous pollutants. The
decipol is the evaluation of the pollutant as determined by the recipient through
the olfactory sensations from the nose. One olf is the emission rate of biological
effluents from one standard person, or the equivalent from other sources. One
decipol is the pollution caused by one standard person when ventilated with
101/s of unpolluted air.
Office accommodation normally has one person for each 10 m
2
of floor
area, so the biological effluent pollution load produced by normal occupancy is
0.1 olf/m
2
. Smokers, building and furnishing materials and ventilation systems
add to the pollution load. The average pollution in an existing building that has
40% of the occupants as smokers produces a load G of 0.7 olf/m
2
. A low-
pollution building with an absence of smoking has a load G of 0.2 olf/m
2
.
When there is complete mixing of the ventilation air with the air in the room,
the rate of supply of outdoor air that is necessary to maintain the required stan-
dard of air.
Comfort criteria
The main comfort criteria for sedentary occupants in buildings in climates
similar to that of the British Isles are as follows:
1). The dry resultant temperature should be in the range 19-23 ° C de-
pending on room use.
2). A feeling of freshness is produced when the mean radiant temperature
is slightly above air temperature. A significant amount of radiant heating is
needed in order to achieve this.
3). The air temperature and the mean radiant temperature should be ap-
proximately the same. Large differences cause either radiant overheating or ex-
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