What Hazards of Static Electricity in Clothing You Need to Know?
During normal production activities, the clothing worn by operators comes into contact with external surfaces (such as workbenches, chairs, tools, and utensils), between layers of clothing, between underwear and skin, and even between shoe soles and the ground. Frequent contact, separation, and friction cause clothing and shoes to become charged, especially when wearing highly insulating synthetic fabrics, which exacerbates this charging. The static charge locally carried on clothing and shoes gradually dissipates across the entire surface according to the law of charge dissipation on a medium, eventually forming a certain static voltage on the clothing.
Of course, since the human body is a good conductor, the charge from clothing can cause the skin to become charged due to electrostatic induction, also forming a certain static voltage. Therefore, for operators, there are two possible discharge paths: one is the discharge between the fingertips (skin) and a grounded conductor, and the other is the discharge between the work clothes and a grounded conductor. Both types of discharge can damage electrostatic sensitive devices. While anti-static wrist straps can eliminate the first type of discharge hazard, they cannot eliminate the second. This is because wristbands can only eliminate static electricity from human skin, which is a good conductor, and cannot dissipate static electricity from clothing, which is more insulating. People often only focus on eliminating static electricity from human skin, neglecting or not giving enough attention to eliminating static electricity from clothing, which needs improvement.
The table below shows the measured range of static voltage on clothing when the operator performs different actions:
**Type of Charge** | Static Voltage on Clothing (V)
**Walking on a normal cement floor in leather shoes (normal speed)** | 1200~1500
**Walking on a normal cement floor in plastic slippers (normal speed)** | 2500~2600
**Working at a desk on a synthetic rubber workbench** | 750~2000
**Slightly rocking on an artificial leather upholstered chair** | 1500~2800
**Sliding on an artificial leather upholstered chair** | 1500~2800
**Suddenly standing up from a chair** | 3800~4500
**Removing outer clothing** | 5000~7000
As can be seen from the table, the static voltage on clothing during various activities greatly exceeds the electrostatic discharge damage threshold of many electrostatic sensitive devices. Therefore, touching or approaching these devices may cause damage. It should also be pointed out that the common belief that wearing pure cotton work clothes can prevent the accumulation of static electricity and therefore ensure safety is a one-sided view. This is only generally true when the relative humidity is above 50%; when the relative humidity is relatively low, the charge on pure cotton products increases significantly. Experiments show that when the relative humidity is below 30%, the charge on pure cotton fabrics is comparable to that of polyester; and when the relative humidity is below 20%, the charge on cotton fabrics can even be higher than that of some synthetic fiber fabrics. Therefore, in dry climates, one cannot expect to eliminate the hazards of static electricity in clothing with pure cotton products under all circumstances.
Based on the above reasons, to effectively prevent the hazards of electrostatic discharge from the human body, operators must wear anti-static work clothes.