Nonconductive plastics and other nonconductive materials should be avoided in areas where flammable vapors, gases or powders may be present since static charges can accumulate on nonconductors. However, it is not always possible to completely eliminate nonconductors, so the following lists some of the ways to reduce the static hazard associated with these materials:
- When it is necessary to use plastic sheeting, bags or liners in an area that is electrically classified, only plastics that have been specially formulated to be static dissipating should be used. To be static dissipating, a plastic film must have a surface resistivity between 106 ohms/square and either 1.0 × 109 or 1.011 ohms per square with the upper limits being given for 23 C and 50% or 20-30% RH, respectively. (ASTM D257) CAUTION!!! It is important to have assurances from the supplier of the static dissipating plastic bags that the bags meet these specifications or equivalent specifications.
- REMOVE shrink and stretch wrap from materials in a non-hazardous area and let them “relax” for a few hours before bringing them into electrically classified areas.
- When dumping plastic bags of powders, the bag MUST NOT be shaken to remove the residual powder. Shaking can result in a very rapid high level of charge generation.
- Avoid rubbing, brushing, or excessively handling plastic bags of ingredients.
- Ensure that ALL conductors in the vicinity of powder transfer operations are GROUNDED, INCLUDING WORKERS.
- Where possible, substitute grounded conductors for nonconductive objects (e.g., use a grounded metal drum for trash instead of a plastic drum).
- Because of the risk of generating a static discharge, articles of clothing or PPE (e.g., jackets, aprons, coveralls) should NOT be removed in areas where flammable vapors may be present.
- If floors in electrically classified areas must be coated, use static dissipative or conductive coatings.