MSHA HANDBOOK SERIES - PH13-V-1 - Mine Safety and Health ...

GENERAL COAL MINE INSPECTION PROCEDURES AND
INSPECTION TRACKING SYSTEM HANDBOOK CHAPTER 5
starts timing, with a stopwatch, how long the smoke cloud takes to travel over
the specified distance.
d. If a stopwatch is not available, use a watch with a sweep second hand. In this
case, the downstream person should signal for release of the smoke cloud when
the second hand reaches a reference point.
e. Record the time interval from the release of the smoke until the leading edge
(front) of the smoke cloud reaches the downstream person. The leading edge is
used because the first part of the smoke should just be leaving the tube and
starting to travel downstream in the air current when the timing begins.
f. Divide the airway cross section into four quadrants and time smoke clouds in
each of the four quadrants. (Refer to Figure 5-2.) Make at least one measurement
at the center point of each quadrant. Make several measurements in each
quadrant for greater accuracy.
Figure 5-2: Section Showing Quadrants (below)
Release 1 (February 2013) 5-6