The Best ESD Floors For Cleanrooms/Labs Prevent Static Generation
Multiple studies show that ESD carpet and EC (electrically conductive) rubber are the only ESD floors—also known as antistatic floors or static-control floors—that inhibit static generation without the use of special ESD footwear. Like the tiny brushes inside a copy machine, the yarn in ESD carpet sweeps static away from shoe soles and the wheels of rolling objects, preventing static generation and the accumulation of harmful static charges also called body voltage.
Electrically conductive (EC) rubber, as determined by independent laboratory tests like ASHRAE, is the only naturally low static-generating resilient flooring material. Research shows that the possibility of generating over 500 volts while walking on a conductive rubber floor is close to zero.
An ASHRAE-funded study looked at the probability of generating a charge over 500 volts while walking on various types of static-control floor wearing ordinary shoes. ASHRAE calculated the probability of generating 500 volts on a static dissipative vinyl floor at 35%; on a conductive vinyl floor, 8%. The probability of a conductive rubber floor generating a charge over 500 volts was only .1%.
Summary Data in Probability for Voltages Greater Than a Threshold Value (Based on Fitted Lines)
| Type of data center | 500 volt discharge probability | 4,000 volt discharge probability | 8,000 volt discharge probability | |||
| 15% RH and 59°F | 50% RH and 80°F | 15% RH and 59°F | 50% RH and 80°F | 15% RH and 59°F | 50% RH and 80°F | |
| No Static Control | 18% | 0.2% | 0.5% | 3.7 x 10-6% | 0.1% | 3.2 x 10-8% |
| Dissipative Floors, Dissipative Footwear | 16% | 19% | 0.016% | 1.0 x 10-4% | 5.5 x 10-5% | 2.2 x 10-7% |
| Dissipative Floors, Uncontrolled Footwear | 34% | 44% | 0.9% | 0.001% | 0.09% | 2.3 x 10-5% |
| Conductive Floors, Dissipative Footwear | 0.003% | 1.6 x 10-7% | 1.8 x 10-7% | 1.8 x 10-11% | 7.4 x 10-9% | 8.9 x 10-13% |
| Conductive Floors, Uncontrolled Footwear | 8% | 0.1% | 0.004% | 4.7 x 10-10% | 4.1 x 10-5% | 7.5 x 10-13% |
| Conductive Rubber Floors, Dissipative Footwear | 0.003% | 1.6 x 10-7% | 1.8 x 10-7% | 1.8 x 10-11% | 7.4 x 10-9% | 8.9 x 10-13% |
| Conductive Rubber Floors, Uncontrolled Footwear | 0.1% | 9.6 x 10-13% | 8.6 x 10-7% | 1.4 x 10-20% | 1.6 x 10-8% | 3.5 x 10-23% |
Source: Determination of the Effect of Humidity on the Probability of ESD Failure or Upset in Data Centers, Moradian et al, 2014
What does low static generating mean and how is low static generation different from conductivity?
When people or rolling objects move across a floor, the friction between the surface of the floor and the shoe soles or the wheels generates static electricity, called walking body voltage. Static builds as they move, and discharges to the first person or object they touch. This static discharge or exchange of electrons is called ESD. ESD is an acronym for electrostatic discharge.
For humans to perceive a static charge, or feel a static shock, the charge must be at least 3 – 4000 volts. A charge of only 500 volts (for telecom or other end-user equipment), down to a mere 10 volts for hyper-sensitive Class-0 microelectronics, can damage or destroy circuitry inside electronic equipment.
When we say a floor is “antistatic” or “low static generating,” we mean that the floor generates very little static and inhibits static charges from building on people or objects as they move across the floor. Static generation is measured in volts, using an electrostatic field meter, following the procedure outlined in STM97.2.
Maximum Voltage requirements
Telecom and other end-user spaces: < 500 volts
Electronics manufacturing and handling: < 100 volts
Class-0 electronics: < 10 volts
What is Walking Body Voltage?
When people or rolling objects move across a floor, the friction between the surface of the floor and the shoe soles or the wheels generates static electricity, called walking body voltage. Static builds as they move, and discharges to the first person or object they touch. This static discharge or exchange of electrons is called ESD. ESD is an acronym for electrostatic discharge.
Conductivity
Conductivity refers to the ability of a flooring material to transport static charges to ground. Floors that inhibit electrostatic discharge, also called static-control floors or ESD floors, contain some type of conductive material – conductive yarn or carbon particles, for instance – introduced into the flooring material in the manufacturing process. These conductive elements draw static away from shoe soles or the wheels on moving carts, transport charges from the surface of the floor, through its thickness, to the underlying conductive groundplane—i.e., GroundBridge underlayment or some type of conductive adhesive. Static charges move across the ground-plane, to copper strips at the perimeter of the room to an earth ground. This is what we mean when we say that an ESD floor “grounds” people and objects.
We learn about a floor’s conductivity by measuring its electrical resistance. Resistance is the opposite of conductivity: that is, the ability of a floor to resist electrical charges. We measure electrical resistance in ohms, using an ohm meter, following the procedure outlined in STM7.1.
Resistance requirements
Electronics manufacturing and handling: < 1.0 x 10E9 ohms
Telecom, networked office spaces, FAA and other end-user spaces: 1.0 x 10E6 – 1.0 x 10E9
Explosives and munitions: 25,000 – < 1.0 x 10E6
What is Conductivity in an ESD Floor?
Conductivity refers to the ability of a flooring material to transport static charges to ground. Floors that inhibit electrostatic discharge, aka static-control floors or ESD floors, contain conductive materials – conductive yarn or carbon particles, for instance – introduced in the manufacturing process. Conductive elements draw static away from shoe soles or the wheels on moving carts, transport charges from the surface of the floor, through its thickness, to the underlying conductive groundplane to an earth ground. This is what we mean when we say an ESD floor “grounds” people and objects.
Conductive and antistatic are not the same
When we say an ESD floor is conductive we are not saying it is antistatic. A conductive floor may be antistatic. A conductive floor may also be a static generator. When people walk on certain types of conductive floors, even if the floor has inherent conductivity (conductive elements added in the manufacturing process), the floor may still generate static on people and rolling objects. This is because the base materials in these floors like pvc or polyurethane generate static. To inhibit static, every person walking on these floors must wear special ESD-protective footwear.
ANSI/ESD S20.20 requires the use of ESD footwear in electronics manufacturing and handling spaces.
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StaticWorx high-performance static-control floors protect electronic components, explosives, and high-speed computers from damage caused by static electricity. ESD flooring is part of a system. Choices should always be based on objective, researched evidence. When you partner with us, we look at all possible items that may need to integrate with the floor, and, focusing on your goals and objectives, help you find the right floor for your application.
