PPV Set-up Procedures continued…
Remember that these guidelines have been
generalized and that optimum efficiency is easily
obtained by a combination of training and
experience.
Exhaust
If a gasoline-powered blower is being utilized and
a gasoline-exhaust odor is noticeable inside the
building or area to be ventilated, this is an
indication that the building's exhaust opening is
not large enough. The gasoline-exhaust odor
should disappear by increasing the size of the
building's exhaust opening (opening another
window, door, etc.)
Weather
Temperature, humidity, snow, and rain do not
have any appreciable effect on positive pressure
ventilation. Although cold, damp weather
conditions may limit the ability of smoke to rise;
these atmospheric conditions will not limit the
ability of blowers to move contaminants
horizontally and, in most cases, vertically.
Wind can have an adverse effect on positive
pressure ventilation, but its effect is dependent on
direction and velocity. As in any ventilation
operation, maximum efficiency can be obtained
by using the prevailing wind direction to
advantage by pressurizing the structure on the
windward side and exhausting contaminants on
the leeward side of the building. If it is not
possible to utilize the prevailing wind as an
advantage, positive pressure has proven effective
against winds of up to 25 mph. As winds exceed
25 mph, efficiency reduces accordingly.
PPV
Set-Up
Procedures
6.6
