Ventilation is the primary control for most hazardous
atmospheres. For a confined or enclosed space to be considered "Safe for
Workers:"
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Maintain oxygen content between 19.5 and 22 percent [1915.12(a)(3)],
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Maintain atmospheres in spaces where flammable vapors or gases may be present below 10 percent of the LEL [1915.12(b)], and
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Maintain air concentrations of potentially toxic materials
below the PEL or IDLH levels [1915.12(c)].
Ventilation may be provided by:
Some operations, such as hot
work, have specific ventilation requirements.
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Dilution Ventilation |
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.
The following are examples of dilution methods:
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Air movers powered by compressed air
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Electric fans and blowers
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Natural ventilation
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Figure 1: Compressed air powered
air movers
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Maritime
Labor/Industry Recommendations |
- Evaluate the hearing protection need of workers when using
portable air movers.
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Visual Inspection |
Exhaust ventilation can be used to remove flammable and toxic fumes, vapors,
and particulates from the space.
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
equipment:
- Electric ducted fans and blowers
- Electric non-ducted fans and blowers
- Air ejector operated by compressed air
Figure 3: Electric non-ducted blower. |
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Figure 4: Air movers provide general
ventilation to confined spaces. |
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Figure 1: Electric ducted exhaust
ventilation.
Figure 2: Electric ducted exhaust ventilation. |
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