3. Low Velocity Air Measurements
(timed smoke clouds)
14 sec 12 sec
13 sec 16 sec
13 sec 15 sec
14 sec 14 sec
13 sec 14 sec
14 sec 15 sec
The time it took the leading edge of the
smoke cloud to travel 10 feet was
recorded (4 times in each quadrant).
8.0’
8.2’
7.9’
19.7’
The dimensions of
the mine entry were
measured.
H + H + H 1 3 2
Average H =
(sum of all times)
Average time =
A = W x H
(number of times)
(distance)
60 sec
Average V = x
x 0.9
(average time)
1 min

4. Low Velocity Air Measurements
(timed smoke clouds)
8.0’
8.2’
7.9’
19.7’
The dimensions of
the mine entry were
measured.
14 sec 12 sec
13 sec 16 sec
13 sec 14 sec
14 sec 15 sec
H + H + H 1 2 3
14 sec 14 sec
13 sec 15 sec
13 sec 15 sec
Average H = 3
The time it took the leading edge of the
smoke cloud to travel 10 feet was
recorded.
8.0’+8.2’+7.9’
Average H =
= 8.0’ 3
(223 sec)
Average time =
= 13.9 sec
A = W x H
(16)
A = 19.7’ x 8.0’
(10’)
60 sec
Average V = x
x 0.9
(13.9 sec)
1 min
A = 158 sq.ft.
Average V = 39 fpm
q = V x A
q = 39 fpm x 158 sq.ft. = cfm

5. Low Velocity Air Measurements
(timed smoke clouds)
14 sec 13 sec
14 sec 15 sec
no movement
4.5’
4.7’
4.4’
20.4’
15 sec 14 sec
13 sec 14 sec
no movement
The dimensions of
the mine entry were
measured.
The time it took the leading edge of the
smoke cloud to travel 5 feet was
recorded (4 times in each quadrant).
H + H + H 1 3 2
Average H =
(sum of all times)
(number of times)
Average time =
A = W x H
(distance)
(average time)
Average V =
60 sec
1 min x
x 0.9

6. Low Velocity Air Measurements
(timed smoke clouds)
4.5’
4.7’
4.4’
20.4’
14 sec 13 sec
14 sec 15 sec
The dimensions of
the mine entry were
measured.
no movement
15 sec 14 sec
13 sec 14 sec
no movement
H + H + H 1 2 3
Average H =
The time it took the leading edge of the
smoke cloud to travel 5 feet was
recorded. 3
4.5’+4.7’+4.4’
Average H =
= 4.6’
(112 sec) 3
Average time =
= 14 sec
(8)
A = W x H
(5’)
60 sec
A = 20.4’ x 4.6’
Average V = x
x 0.9
(14 sec)
1 min
A = 93.8 sq.ft.
(93.8 sq.ft.)
Average V = 19 fpm
Effective Area = 2
Effective Area =
47 sq.ft.
q = V x A
q = 19 fpm x 47 sq.ft. = 893 cfm