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C. Ventilation Of Confined Spaces
is one of the most effective means of controlling hazardous atmospheres
in confined spaces. In this procedure, clean air replaces contaminated
air by natural or forced (mechanical) ventilation.
a confined space, the following factors must by taken into consideration:
air: This determines the capacity of the blower or ejector.
Type of atmosphere:
This will determine the type of blower or ejector used and the length
of time needed to ventilate until it is safe for people to enter
space: This determines how to get the ventilating air into and
out of the space.
and availability: This will influence the power source and fan
motor size. A portable generator may be required as a source of
and maintenance: This may have an effect on the type of device
that is selected and what is necessary to keep it working properly.
space: This will affect the typed of directional device needed
and the amount of air pressure required to provide sufficient ventilation.
clean air: This is necessary to ensure adequate ventilation.
time ventilation is needed: This is determined by the type of
contaminant and the work that is to be done in the space
Type of work
to be done: This determines whether local exhaust ventilation
or general ventilation is required.
fan with a capacity to quickly replace the air in the space.
Limitations are pasted on the fan housing
reliable, grounded electrical power.
any hazardous atmosphere. Exhaust toxic and flammable air; supply
fresh air when oxygen-deficient.
constant circulation of fresh air while space is occupied.
ventilation is allowable only on "non-permit"
high-velocity supply ventilation to mix the air throughout
contaminants during hot work or cleaning with solvents by
using additional local (or point) exhaust.
oxygen is not "fresh air". Never use bottled oxygen
ductwork to ensure safety:
supply fan intake away from flammable or toxic air.
exhaust fan outlet to avoid recirculation of bad air or
endangering others outside the space.
exhaust duct inlet next to the source of contaminants.
ducts short and straight.
sure air circulates through entire space and does not short-circuit.
the air to ensure ventilation is keeping the air safe to breathe.
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