12
MEASURING INLET SLOT VELOCITY
Smoke capture and grease extraction efficiency are de-
pendent upon the proper air velocity at the inlet slot of the
ventilator.The required average slot velocities are shown
on the “Air Velocity Chart” below. If the slot velocity is
below the required average, the exhaust fan must be
adjusted accordingly.
NOTE: The height of the inlet slot can vary depending
upon the design of the ventilator. It is, therefore, important
to first measure the inlet slot and compare it to the chart
below to determine the required average inlet slot veloc-
ity. The designed CFM per lineal foot is related to the
velocity as shown on the chart below. The total CFM for
the ventilator can be found on the ventilator nameplate.
(See Figure 6).
Air velocity readings less than what is specified on the “Air
Velocity Chart” may allow smoke and grease to escape
the confines of the ventilator and/or reduce grease extrac-
tion efficiency. This can result in grease deposits which
lead to sanitation problems or fire hazards if left uncor-
rected. If air velocity readings are higher than those
specified, it will require more energy to operate the
exhaust fan and excessive noise levels will result. Higher
or lower velocities than the required average will normally
put the entire heating and ventilating system out of bal-
ance. When measuring the air velocity it is very important
to take an average reading across the inlet slot plane as
described on Page 13. Positioning the sensing head
incorrectly will give velocity readings that cannot be com-
pared to the “Air Velocity Chart”.
T
R
A
H
C
Y
T
I
C
O
L
E
V
R
I
A
S
E
I
R
E
S
"
S
D
"
T
P
E
C
X
E
S
E
I
R
E
S
"
2
X
G
"
L
L
A
R
O
F
l
a
n
i
m
o
N
t
h
g
i
e
H
f
o
t
o
l
S
t
e
l
n
I
m
o
t
s
u
C
t
u
o
h
t
i
W
s
e
l
f
f
a
B
r
i
A
m
o
t
s
u
C
h
t
i
W
s
e
l
f
f
a
B
r
i
A
d
e
n
g
i
s
e
D
r
e
p
M
F
C
.
t
F
l
a
e
n
i
L
t
e
l
n
I
e
g
a
r
e
v
A
)
M
P
F
(
y
t
i
c
o
l
e
V
t
o
l
S
.
n
i
M
m
u
m
i
t
p
O
.
x
a
M
d
e
n
g
i
s
e
D
r
e
p
M
F
C
.
t
F
l
a
e
n
i
L
t
e
l
n
I
e
g
a
r
e
v
A
)
M
P
F
(
y
t
i
c
o
l
e
V
t
o
l
S
.
n
i
M
m
u
m
i
t
p
O
.
x
a
M
"
3
)
d
t
S
(
"
4
)
l
n
E
(
0
5
2
0
7
2
5
8
2
0
0
3
0
0
4
0
0
3
1
0
6
3
1
5
2
4
1
5
6
4
1
0
9
6
1
0
8
3
1
5
3
4
1
0
0
5
1
5
4
5
1
0
8
7
1
0
5
4
1
0
0
5
1
5
7
5
1
5
2
6
1
0
7
8
1
0
5
1
0
6
1
0
7
1
0
8
1
0
5
2
0
6
7
0
9
7
0
1
8
5
4
8
0
4
0
1
0
0
8
0
3
8
5
5
8
0
8
8
5
9
0
1
0
8
8
0
7
8
0
0
9
5
3
9
0
5
1
1
MEASURING INLET SLOT VELOCITY
*
S
R
O
T
A
L
I
T
N
E
V
S
E
I
R
E
S
"
S
D
"
R
O
F
r
e
P
M
F
C
d
e
n
g
i
s
e
D
.
t
F
l
a
e
n
i
L
t
e
l
n
I
e
g
a
r
e
v
A
d
e
r
i
u
q
e
R
)
M
P
F
(
y
t
i
c
o
l
e
V
t
o
l
S
l
a
t
o
T
h
t
o
B
s
t
o
l
S
t
n
o
r
F
t
o
l
S
r
a
e
R
t
o
l
S
t
o
l
S
t
n
o
r
F
.
n
i
M
m
u
m
i
t
p
O
.
x
a
M
t
o
l
S
r
a
e
R
.
n
i
M
m
u
m
i
t
p
O
.
x
a
M
0
0
3
0
0
4
0
5
1
0
5
2
0
5
1
0
5
1
0
6
7
5
7
3
1
0
0
8
0
5
4
1
0
8
8
0
2
5
1
5
9
5
5
9
5
5
2
6
5
2
6
5
5
6
5
5
6
