may be safely done without enclosures (ref. OSHA
Instruction CPL 2-2.63, change 1, dated 9 January
1996); that is, OSHA does not require enclosures.
An exposure assessment must be made prior to outdoor
work to determine other required controls. Remove
this paragraph when not required in the project.
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In addition to requirements of paragraphs Mandated Practices and Control
Methods, the following engineering controls and work practices shall be
used:
a.
A Competent Person shall supervise the installation and operation
of the control methods.
b.
For jobs involving the removal of more than 7.5 m 25 feet or 0.9
square m 10 square feet of TSI or surfacing material, the
Contractor shall place critical barriers over all openings to the
regulated area.
c.
HVAC systems shall be isolated in the regulated area by sealing
with a double layer of plastic or air-tight rigid covers.
d.
Impermeable dropcloths (0.15 mm 6 mil or greater thickness) shall
be placed on surfaces beneath all removal activity.
e.
Where a negative exposure assessment has not been provided or
where exposure monitoring shows the PEL was exceeded, the
regulated area shall be ventilated with a HEPA unit and employees
must use PPE.
3.6.5
Specific Control Methods for Class I Work
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NOTE: Remove these paragraph and/or subparagraphs
when not required in the project.
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3.6.5.1
Negative Pressure Enclosure (NPE) System
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NOTE: Before specifying a negative pressure
enclosure system, the designer should determine if
an enclosure system is feasible. The enclosure
should be the minimum area to encompass all the
working surfaces yet allow unencumbered movement by
the workers, provide unrestricted air flow past the
workers, and ensure walking surfaces can be kept
free of tripping hazards.
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The NPE system shall be as shown in SETUP DETAIL SHEET [2] [3] [4] [8].
The system shall provide at least 4 air changes per hour inside the
containment. The local exhaust unit equipment shall be operated 24 hours
per day until the containment is removed. The NPE shall be smoke tested
for leaks at the beginning of each shift and be sufficient to maintain a
minimum pressure differential of minus 0.5 mm 0.02 inch of water column
relative to adjacent, unsealed areas. Pressure differential shall be
monitored continuously, 24 hours per day, with an automatic manometric
SECTION 13280A
Page 36
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