1301666501 rev B
Page 3 of 10
Ground Level
Ventilation
Air
Combustion
Air
A
ir
D
uc
t f
ro
m
G
ro
un
d
to
B
as
e
Drip Tee
Gas Cock
Sediment Trap
Level Flooring
or Slab
Rise of 1 inch
per foot
Vent Cap
Free Area per
Btu
Requirement
Total
Input
(btu/hr)
Combustion Air
Free Area
Required
(sq. in.)
Ventilation Air
Free Area
Required
(sq. in.)
150,000
150
150
200,000
200
200
250,000
250
250
300,000
300
300
350,000
350
350
400,000
400
400
150,000
75
75
200,000
100
100
250,000
125
125
300,000
150
150
350,000
175
175
400,000
200
200
150,000
37.5
37.5
200,000
50
50
250,000
62.5
62.5
300,000
75
75
350,000
87.5
87.5
400,000
100
100
150,000
600
600
200,000
800
800
250,000
1000
1000
300,000
1200
1200
350,000
1400
1400
400,000
1600
1600
1 sq. in. per
1,000 btu/hr
(paragraph A)
1 sq. in. per
2,000 btu/hr
(paragraph B-2)
1 sq. in. per
4,000 btu/hr
(paragraph B-1)
1 sq. in. per 250
btu/hr
(paragraph B-4)
TABLE 5
FIGURE 1
EN
G
LIS
H
