6 December 2006
Including change 1, 7 December 2006
Figure 11-1. Sail Method of Manhole Ventilation
11-6.8.3 Natural Method. This method consists of taking the manhole cover off and
letting the internal air escape as much as it can. This method of venting a manhole is
the least effective because a gas heavier than air could remain in the bottom of the
manhole. Use this method of venting a manhole only as an emergency measure, and
only when determined safe.
WORK INSIDE UNDERGROUND STRUCTURES.
Visually inspect for hazardous conditions such as burnt or cut cables, or
loose or defective ladders before starting work. Any signs of cable
damage will require the affected cables to be deenergized before starting
11-7.1.1 Use a ladder when entering or leaving a manhole or vault. Climbing into or
out of manholes or vaults by stepping on cables or cable supports is prohibited. Use of