Ventilation is the primary control for most hazardous
atmospheres. For a confined or enclosed space to be considered "Safe for
Ventilation may be provided by:
Some operations, such as hot
work, have specific ventilation requirements.
Maintain oxygen content between 19.5 and 22 percent [29 CFR 1915.12(a)(3)],
Maintain atmospheres in spaces where flammable vapors or gases may be present below 10 percent of the LEL [29 CFR 1915.12(b)], and
Maintain air concentrations of potentially toxic materials
below the PEL or IDLH levels [29 CFR 1915.12(c)].
Dilution Ventilation can be
used to reduce concentrations of flammable and toxic
fumes, vapors, or particulates. Additionally, acceptable oxygen content can be achieved and
maintained by introducing outside air.
Figure 1: Compressed air powered air movers.
The following are examples of dilution methods:
Air movers powered by compressed air
Electric fans and blowers
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- Evaluate the hearing protection need of workers when using
portable air movers.
Exhaust ventilation can be used to remove flammable and toxic fumes, vapors,
and particulates from the space.
Figure 2: Electric ducted exhaust
Figure 3: Electric ducted exhaust ventilation.
Where mechanical ventilation is
used in potentially flammable atmospheres,
this equipment must be rated as explosion proof by Nationally
Recognized Testing Labs (NRTL).
Make sure that supplied air is from a clean source and
that the hazardous atmosphere is exhausted to safe areas. Keep the ducts
as short and straight as possible for more efficient air movement.
The following are examples of exhaust ventilation
- Electric ducted fans and blowers
- Electric non-ducted fans and blowers
- Air ejector operated by compressed air
Figure 4: Electric non-ducted blower.
Figure 5: Air movers provide general
ventilation to confined spaces.