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Winter 2002 - Article 2

From The Lab
Static Electricity Sparks

From time to time we receive a complaint call about static electricity sparks caused by floor finish. These calls are most common during dry air months. Contrary to popular belief, floor finish does not cause the spark.

This phenomenon happens in very dry air where the relative humidity is less than 25%. Static electricity occurs when the soles of our shoes steal negative ions from the floor (insulator). We leave behind "electrified" positive footprints, and our bodies acquire an overall negative charge imbalance. After many footsteps, such as throughout a supermarket, our bodies attain a high level of electric charge and a very high voltage (10,000 - 40,000 volts)! The next time you touch someone or another object (especially a conductor like store shelving, a metal can or a light switch) you get shocked because the imbalanced charge (negative versus positive) gets shared between you and the object.

To prevent shocks, the negative/positive charge separation must be stopped. This can be done through:

1. Using leather soled shoes (thinner soles are better).
2. Raising the relative humidity in the building above 25%.
3. Mopping floors with antistatic liquid

Mopping floors with antistatic solution has limitations. On hard surfaces, frequent applications are needed to provide optimal performance.

The use of conductive or electrostatic dissipative floor finish will not prevent all static electricity shocks since the finishes are humidity-dependent (most require relative humidity greater than 25%).

Therefore, raising the relative humidity in the environment is the best prevention against static electricity shocks. Raising the humidity can be done through Mother Nature (such as rain or change of season) or through humidifiers.