How to Manage Risks and Ensure Effective Anti-Static Clothing
1. Ensure Clothing is Always Grounded
Without a grounding connection, static charge can jump from clothing to nearby conductive surfaces/materials, potentially damaging equipment or igniting a flammable atmosphere. With this in mind, and regardless of the effectiveness of the surface treatment, wearers of anti-static PPE must consider how the static charge is grounded.
There are three ways static charge is transferred to the earth:
1. Through the Human Body
One way to dissipate static electricity is through the human body (we are primarily made of water), but this relies on constant contact between the wearer's skin and clothing, assuming the wearer's shoes and the floor are conductive.
2. Wearing Clothing with Socks to Ensure Constant Contact with the Floor
Another way to harmlessly discharge static electricity is by wearing anti-static clothing with socks over them, wearing them over regular shoes to ensure constant contact with the floor. (This, of course, assumes the floor is conductive and uninsulated. If the charge cannot be grounded through the floor, then this will obviously not work.)
3. Through a conductive cable clipped to the anti-static clothing and a known grounding point
Finally, a conductive cable (one end clipped to the anti-static clothing and the other to a known grounding point) can harmlessly transfer static charge to the earth.
However, even with the above routes, it is crucial that the surface resistance of the grounded surface is low to allow the charge to dissipate.
2. Controlling Ambient Humidity
The EN test for surface resistance (EN 1149-1) is conducted at 25% relative humidity, which is very low – particularly because less moisture is available to form a conductive film, making surface treatment more challenging. In real-world environments, humidity levels are often much higher than this, so anti-static treatments can be more effective (i.e., lower surface resistance) than the test indicates. However, in extreme cases where anti-static treatment is critical, or where dry air is common, it may be important to monitor and, if possible, control humidity to ensure treatment effectiveness. "
Third, limit use, do not reuse garments, and inspect them regularly.
Continued use of anti-static clothing-especially in environments where wear and tear is a critical concern-will degrade the anti-static function, and damaged work clothing will no longer protect the wearer. If anti-static clothing is used for extended periods, it is recommended to replace it regularly with a new garment, as any surface treatment will fade or rub off. Suits should not be reused, as washing or decontamination will eliminate the anti-static treatment.
Ideally, safety managers should conduct routine inspections of anti-static equipment and the environment to ensure that anti-static clothing is in good condition and that there is sufficient moisture in the environment to promote effective protection.
Finally, in high-risk areas, such as explosive atmospheres, anti-static performance becomes even more important, as static discharge when charges jump from clothing to another surface can cause ignition. While protective clothing certified to anti-static standards is recommended, this may not be sufficient. Further reducing the potential for static sparks from clothing by more effectively managing its use should be a key consideration.
Ultimately, in high-risk areas where clothing relies solely on surface treatment for high anti-static performance, it may not be sufficient; perhaps specialized clothing with inherent anti-static properties should be considered.