- (01-21) -
4-3. METHODS OF VENTILATION
Ventilation can be divided into natural ventilation based
on natural conditions and mechanical ventilation based on
mechanical power.
NATURAL VENTILATION
This ventilation is based on pressure
derived from external winds and
the outdoor and indoor temperature
differences. However, as natural
ventilation is weaker than mechanical
ventilation and may be greatly
affected by natural conditions,
significant results cannot be expected
MECHANICAL VENTILATION
Methods of mechanical ventilation
As this method is based on enforced
ventilation with ventilating fans and air
blowers, etc., it is capable of generating
stable amounts of ventilation at
required timing, compared with natural
ventilation.
*
Highly contaminated rooms should
remain in negative pressure to prevent
contaminated air from leaking into
adjacent rooms and corridors (Class 1 or
Class 3 Ventilation). On the other hand,
for rooms that need to be kept clean,
positive pressure should be maintained
to prevent intrusion of contaminated air
(Class 2 Ventilation).
Total ventilation and local ventilation
Total ventilation
This ventilation is designed for an
entire house and for exchanging
the entire air in the house (Fig.
3-5).
The total (general) ventilation can be categorized into the
following three types.
a) Individualized ventilation system
The amount of ventilation required for each room can be
satisfied by installing ventilation facilities at each room.
.………
b) Total ventilation system
The total amount of ventilation for the entire building
can be satisfied by utilizing local exhaust facilities and
installing natural air-supply inlet at each room. E.g., local
exhaust faci natural air-supply inlets, etc.
c) Central ventilation system
A single ventilation unit can satisfy the amount of
ventilation required for multiple rooms and the entire
building. …………
Natural air
exhaust
Natural air
supply
Air exhaust
Air supply
(Natural
ventilation)
Fig. 3-1
Warehouses, gymnasiums, factories
where hot air is generated
Class 1 Ventilation Method
Exhaust
Mechanical
exhaust
Air
supply
Mechanical air
supply
Indoor
Ventilating fan
Exter-
nal air
Ventilating
fan
To be applied for buildings, indoor parking
lots, boiler rooms, electric rooms, machine
rooms, kitchens, and warehouses, etc.
Fig. 3-2
Class 2 Ventilation Method
Exhaust
Mechanical
exhaust
Air
supply
Mechanical air
supply
Class 3 Ventilation Method
Exhaust
Mechanical
exhaust
Air
supply
Mechanical air
supply
Exter-
nal air
Exter-
nal air
Positive
pressure
Exhaust
outlet
Indoor
Ventilating fan
Indoor
Fig. 3-3
Negative
pressure
Air supply
inlet
Ventilating
fan
Fig. 3-4
To be applied for clean rooms and cooling
machinery, etc.
To be applied for kitchens, toilets, rooms where hot-water
heaters can be utilized in residences, and copying
rooms, etc.
Class 1 Ventilation Method
Exhaust
Mechanical
exhaust
Air
supply
Mechanical air
supply
Indoor
Ventilating fan
Exter-
nal air
Ventilating
fan
To be applied for buildings, indoor parking
lots, boiler rooms, electric rooms, machine
rooms, kitchens, and warehouses, etc.
Fig. 3-2
Class 2 Ventilation Method
Exhaust
Mechanical
exhaust
Air
supply
Mechanical air
supply
Class 3 Ventilation Method
Exhaust
Mechanical
exhaust
Air
supply
Mechanical air
supply
Exter-
nal air
Exter-
nal air
Positive
pressure
Exhaust
outlet
Indoor
Ventilating fan
Indoor
Fig. 3-3
Negative
pressure
Air supply
inlet
Ventilating
fan
Fig. 3-4
To be applied for clean rooms and cooling
machinery, etc.
To be applied for kitchens, toilets, rooms where hot-water
heaters can be utilized in residences, and copying
rooms, etc.
Class 1 Ventilation Method
Exhaust
Mechanical
exhaust
Air
supply
Mechanical air
supply
Indoor
Ventilating fan
Exter-
nal air
Ventilating
fan
To be applied for buildings, indoor parking
lots, boiler rooms, electric rooms, machine
rooms, kitchens, and warehouses, etc.
Fig. 3-2
Class 2 Ventilation Method
Exhaust
Mechanical
exhaust
Air
supply
Mechanical air
supply
Class 3 Ventilation Method
Exhaust
Mechanical
exhaust
Air
supply
Mechanical air
supply
Exter-
nal air
Exter-
nal air
Positive
pressure
Exhaust
outlet
Indoor
Ventilating fan
Indoor
Fig. 3-3
Negative
pressure
Air supply
inlet
Ventilating
fan
Fig. 3-4
To be applied for clean rooms and cooling
machinery, etc.
To be applied for kitchens, toilets, rooms where hot-water
heaters can be utilized in residences, and copying
rooms, etc.
Air
supply
Contami-
nated air
Ex-
haust
Fig. 3-5
Local ventilation
This type of ventilation is performed for particular spots in a
house (rooms or parts).
a) Local exhaust
Local exhaust is performed for particular places in which
contaminants (combustion gases, humidity, smoke, and
smell, etc.) may be generated (Fig. 3-6).
(Ohmsha, Ltd., Ventilation, the
Society of Heating, Air-Conditioning
and Sanitary Engineers of Japan)
This kind of ventilation is applied
specifically for kitchens, bathrooms,
and toilets, etc.
a) Room ventilation
Individualized ventilation designed for single rooms, etc.
(When individualized ventilation systems are installed
in all rooms, the entire setup can be referred to as total
ventilation.)
Cooking o
hood fan
ven
Th
e
ra
ng
e
co
ve
re
d
by
ve
nt
ila
tio
n
Exhaust
Oven
Fig. 3-6
