MIL-HDBK-1028/8A
prior to entry into the mixing and storage areas. Extended shut down of
the system is not recommended except for maintenance and repair. Entry
into an pesticide storage area after extended shut down of the
ventilation system would result in exposure to maximum vapor
concentration.
3.5.4.3
Mixing Sink Exhaust System. Provide a slotted hood, local exhaust
system for the mixing sink as shown on Facility Plate 10. The exhaust hood
shall provide an air velocity of 150 linear feet per minute (fpm) (0.76 m/s)
at face of the hood (29 CFR 1910.106). Baffles or plenums should be used to
maintain a uniform face velocity. If multiple stacked slots are used, the
upper slots will have a higher air volume (cfm) unless provisions are made to
ensure that the lower slots provide 150 fpm (0.76 m/s) capture velocity at the
outer edge of the counter or sink top. Sink and exhaust hood shall be
stainless steel. Specify either stainless steel or fiberglass reinforced
plastic (FRP) ductwork and a centrifugal FRP exhaust fan with backward
inclined blades. The fan shall be roof mounted and have a vertical "no loss"
discharge stack (see ACGIH Industrial Ventilation manual). Top of stack shall
be 30 percent higher than the roof elevation. The replacement air system
shall provide approximately 95 percent of the air exhausted through the hood
to maintain a negative pressure in the mixing room relative to the clean
areas. Replacement air shall be heated to 55 degrees Fahrenheit (13 degrees
Celsius). Exhaust fan and replacement air fan shall be activated by the same
switch. It is critical that replacement air is introduced into the room at
low velocity to minimize turbulence around the exhaust hood (refer to
MIL-HDBK-1003/17, Industrial Ventilation Systems, for design of the
replacement air system). Provide a motorized damper at the air intake louver
and at the exhaust fan discharge. Damper shall close when the ventilation
system is turned off.
Operational Note: For upgrading existing facilities, exposure hazards
from toxic vapors shall be engineered out with the installation of an
exhaust fan or duct directly opposite the mixing surface from the
worker. Stainless steel hoods are recommended because they last longer
in a corrosive environment. Personal protective equipment (respirator,
face mask or shield, gloves, apron and work clothing) may be used to
provide interim protection during mixing operations, but proper
engineering controls to correct such deficiencies in plumbing or
ventilation systems described above should addressed immediately or
placed on an abatement program for correction.
3.6
Electrical. Design shall be in accordance with the National
Electrical Code (NFPA) 70 and MIL-HDBK-1004/1, Preliminary Design
Considerations, MIL-HDBK-1004/2, Power Distribution Systems, MIL-HDBK-1004/3,
Switchgear and Relaying, MIL-HDBK-1004/4, Electrical Utilization Systems,
MIL-HDBK-1004/6, Lightning Protection, and MIL-HDBK-1004/7, Wire Communication
and Signal Systems.
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