UEi Test Instruments C127OILKIT User Manual
Page 11
r
eSideNtial
S
ourCeS
of
Co
1. Chimney
2. Space Heaters
3. Vehicle exhaust
4. Water Heater
5. Furnace
6. Improperly vented appliances
7. Tobacco products
8. Fireplace (Gas or wood burning)
9. & 10. Gas appliances
S
taCk
e
ffeCt
& N
egative
P
reSSure
Stack Effect
When air escapes through
openings in the upper part of a
building and is replaced with outside
air entering through vents or cracks
lower down. As air warms it expands
and becomes less dense than the
surrounding air, it rises and escapes
through small gaps at the top of the
house. This also draws fresh cold air
through similar gaps or vents at the
bottom of the house. The vacuum
created by escaping warm air is called
the stack effect. When carefully
controlled, stack effect can produce a
low and effective level of natural
ventilation.
Negative Pressure
A tightly sealed house will
indicate a reduction of draft when
venting equipment (clothes dryer,
kitchen hood, bathroom vent) is
turned on during a draft test. If the
air pressure outside is greater than the
pressure within the house, a
vacuum, or negative pressure is
created. This difference in air pressure
will pull air through any available
openings in building walls, ceilings,
floors, doors, windows, and air
circulation systems. If this vacuum is
strong enough it can reverse exhaust
ventilation systems pulling harmful gases in to the house.
1.
3.
4. 5.
6.
7. 8.
9.
10.
2.
10
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