The passive ionisers discharge the material across a very narrow air gap due to the electric field that builds up naturally. However, this physical effect ceases at a certain field strength, as a consequence a passive ionizer does not achieve a deep residual charge. However, the discharge is sufficient to avoid sparks and shocks, but rarely to avoid adhesion (e.g. dirt, other materials etc.) or repulsion (e.g. ink droplet printing or telescoping of foil).