Cold air during winter has low moisture content, and heating inside the plant will decrease relative humidity. Pressrooms and binderies with a relative humidity below 35% are likely to experience static problems. The lower the relative humidity, the greater the potential for static. Static eliminating devices such as air ionizers and copper tinsel have limited effectiveness in reducing static. The paper is always in contact with other sheets or equipment parts and tends to pass the static charge, and the static is not completely eliminated. Humidifying the pressroom to 45-55% relative humidity is the most effective method to prevent and reduce static-related problems. Slightly higher relative humidity levels would benefit static-prone substrates such as synthetics and plastics.