VT PowerPoint Template3

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How to Prevent and Eliminate Mold on Wood Pallets
Peter Hamner Center for Unit Load
Design Virginia Tech
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Effective mold control on wood pallets must begin
with a management commitment to a continuous and
comprehensive mold control program.

• There is no magic bullet to prevent mold from
  growing on green (wet) surfaces of wood pallets.
• Mold can only be prevented and controlled by
  developing and adopting a comprehensive strategy.
  

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MOLD
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Key Components of a Mold Control Program

• Reducing airborne mold spore density
• Reducing wood surface MC to below 20
• Maintaining low wood moisture levels

• Responsibility of mold control program should be
  centralized and assigned to one person !

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Reducing airborne mold spore density
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• Regular inspection of entire premises
• Buildings, grounds, raw materials, and finished
  goods
• 2 times per week
• Mold can occur on any type of surface wood,
  plastic, metal, etc.
• Identify mold spore breeding grounds
• Look for incidences of mold occurring on raw
  materials, finished goods, or other possible
  sources of mold
• Spot treat (spray) any existing mold
• 21 ratio of water and household bleach

• It is recommended that raw material delivery
  specifications include mold free requirements.

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Reducing airborne mold spore density

• Eliminate excess piles of wood debris and any
  other unnecessary materials that could act as
  mold spore repositories.

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Reducing airborne mold spore density

• All manufacturing and storage areas should be
• Well ventilated
• Adequately drained eliminate standing water
• Allow as much ambient light as possible
• Periodically washed with bleach solution

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Dry pallets to an average MC below 25 before
shipping

• Install and incorporate a chemical fungicide dip
  treatment operation.
• Purpose is to provide an effective chemical
  barrier to prevent mold and to allow time for
  drying
• Most effective to treat dead stacked parts.
  Assembled pallets can be dipped as well.

Chlorine bleach will not kill mold sporesit does
not prevent mold from returning quickly (1-2
days).
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Dip treating non-banded dead stacked parts with
chemical fungicide. Penetration is effective
through the stack.
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Pallets that appear to be mold free at the time
of shipping, but that still have high moisture
contents, will likely create problems down the
road. Due to the high moisture, mold will begin
to grow at some point, and the customer will
complain.
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Dry pallets to an average MC below 25 before
shipping

• An effective fan drying system can allow green
  hardwood pallets to achieve 20 - 25 average MC
  in 10 days to 3 weeks (depending on ambient air
  temperature and relative humidity).
• Any accelerated drying options are best !

Fan shed
HT chamber
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• Inside of fan shed pallets stacked in neat rows
  with pallet ends oriented to allow maximum air
  flow across surfaces.

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Dry pallets to an average MC below 25 before
shipping

• Fan sheds in combination with chemical dip
  treatments have proven very effective at
  preventing mold growth on pallets
• Must keep dry during shipment, and future storage
  and use
• Must educate your customer !!!

• Note mold will not grow on frozen pallets in
  winterbutif they are stored in heated
  structures (above freezing, they will support
  mold growth)

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Dry pallets to an average MC below 25 before
shipping

• MC should be recorded and tracked on a regular
  basis to determine effectiveness of moisture
  control program.
• Electrical resistance meters can be used to
  monitor MCs below fiber saturation (30).
• Random samples of each production run should be
  measured and recorded twice weekly (in the drying
  area).

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For surface MC measurement of deckboards and
stringers
For core MC measurements in stringers
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Heat Treating
Heat treating without venting can increase mold
problems.
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Heat Treating

• A fully vented blow down cycle (at least 30
  minutes) is recommended at the end of the HT
  cycle to dry wood surfaces.
• After heat treating, pallets should be moved
  immediately to a covered fan drying area.

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Maintain low wood surface moisture levels
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• Maintain a sufficient inventory of mold free
  pallets that have been dried to an average MC of
  below 25.

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Maintain low wood surface moisture levels

• The best option for shipping mold free pallets is
  ventilated chip vans.
• Chip vans prevent humidity from rising and
  condensation from occurring inside a truck
  trailer when pallets are inside.
• Also prevent rain contamination
• Pallets should not remain in closed trailers for
  more than 24 hours.

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Maintain low wood surface moisture levels

• Upon delivery, pallets should be removed from the
  trailer and stored and protected from rain in a
  well lit, well ventilated area with good
  drainage.
• Never leave pallets (even sufficiently dry
  pallets) locked up in a closed trailer over the
  weekend.

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REVIEWKey factors of successful mold control
program

• Reduce airborne mold spore density
• Reduce wood surface MC to below 20
• Maintain low wood moisture levels

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• These procedures should be applied to the entire
  scope of the manufacturing, storage and shipping
  operation (for all pallets).
• If not feasible, apply the mold strategy to
  pallets that have mold free requirements and
  keep them segregated from other pallets during
  storage, treatment, and shipment.

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• Pallets that have been successfully manufactured
  and delivered mold free can never be guaranteed
  to remain mold free !!!
• Its important that your customers understand
  that they have a role in maintaining mold free
  pallets.

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Questions ??????