ANSI/ESD S20.20 sets two flooring requirements, and most specifications only mention the first. The floor must measure less than 1.0 × 10⁹ ohms resistance when tested to ANSI/ESD STM7.1, and the footwear-and-flooring system must generate less than 100 volts of body voltage during a defined walking test to ANSI/ESD STM97.2.
That second requirement is the one that catches facilities out. A floor can pass its resistance measurement comfortably and still fail S20.20, because resistance tells you whether a charge can drain away while body voltage generation tells you whether a charge is accumulating on your operators in the first place. Since the 2014 revision, both have to be demonstrated.
The Numbers
Floor resistance
Measured to ANSI/ESD STM7.1, which is the flooring test method standard that sits alongside S20.20.
- Conductive flooring — 1.0 × 10⁶ ohms or below. Fastest discharge path, used where charge must be removed as quickly as possible.
- Static dissipative flooring — above 1.0 × 10⁶ and below 1.0 × 10⁹ ohms. Controlled, slower discharge. The most commonly specified range.
- Anti-static — roughly 10⁹ to 10¹¹ ohms. Resists charge generation but does not actively dissipate.
That last category matters because of how the word is used commercially. A product marketed as “anti-static” in the 10¹⁰ to 10¹¹ range will not pass S20.20 verification in an ESD-sensitive area. If a specification does not state a resistance range in ohms, it is incomplete.
System resistance
The combined resistance of person, footwear, and floor to ground must be below 3.5 × 10⁷ ohms — 35 megohms — measured to ANSI/ESD STM97.1.
Note what this implies: the floor is only half of a system. A compliant floor paired with the wrong footwear produces a non-compliant facility.
Body voltage generation
Under 100 volts, measured to ANSI/ESD STM97.2 using the operator’s actual footwear on the actual installed floor.
This is the requirement that is most telling and most often skipped. It is a walking test with real people in real shoes, not a bench measurement.
Why Resistance Alone Is Not Enough
Before 2014, flooring was commonly qualified on resistance figures alone, on the assumption that a floor within the right range would control charge adequately.
Field testing showed that assumption failing. Floors measuring comfortably inside the dissipative range were recorded generating body voltages several times the 100-volt limit on people wearing functioning ESD footwear. Resistance describes the drain path; it does not describe how much charge the surface generates through contact and separation as someone walks across it.
The practical consequence for anyone specifying a floor: ask for body voltage generation data, not just resistance figures. A supplier who can only provide resistance numbers has only answered half the standard.
Other Standards You May Be Working To
S20.20 is the general ESD control programme standard, but sector requirements differ and sometimes tighten the range:
- IEC 61340-5-1 — the international equivalent, broadly aligned with S20.20
- FAA-STD-019 — aerospace, specifying a band between 10⁶ and 10⁹ ohms
- Telecommunications and data centre standards — several specify their own bands, some extending to 10¹⁰ ohms
Note that some of these set a lower limit as well as an upper one. S20.20 itself does not impose a lower resistance bound for flooring, but sector standards and electrical safety considerations often do, which is why “as conductive as possible” is not the right target.
Testing Conditions Affect Results
Resistance readings are sensitive to how they are taken. Testing to STM7.1 uses defined electrodes, a specified test voltage, and controlled humidity — low humidity conditions in particular, because humidity assists charge dissipation and testing in a humid room can flatter a floor that will underperform in a dry Toronto January.
Two implications:
Ask when the test was done. A floor tested in July may read differently in February.
Ask for written results. Multiple locations, with the conditions recorded. In a facility running a formal ESD control programme, that documentation is part of your compliance record and an auditor will want it.
Verification Is Ongoing, Not One-Off
S20.20 is built around a compliance verification plan. The floor is tested at installation and then periodically thereafter, because ESD flooring properties change over time — most often because of what gets applied to the surface during cleaning.
Ordinary floor finishes and waxes insulate a dissipative floor. A facility can maintain a perfectly compliant floor into non-compliance with a well-meaning cleaning contract. We cover this in how to maintain an ESD floor.
Specifying a Compliant Floor
A complete specification names:
- The target resistance range in ohms, and the test method
- Body voltage generation limit and test method
- The footwear the floor will be used with
- Grounding grid layout and connection points
- Handover testing with written results
- Approved cleaning products and the verification schedule
The grounding point deserves emphasis. Resistance figures describe the floor’s ability to move charge, but that charge needs a verified continuous path to building ground to actually go anywhere. See how ESD epoxy flooring is installed and grounded.
Getting It Right
Armour Guard installs conductive and ESD flooring in Toronto and across the GTA for facilities running formal static control programmes, where the floor has to pass verification rather than simply look the part.
Contact our Toronto team to discuss the standard your facility works to and the system that meets it.
This article summarises publicly documented requirements and is not a substitute for the standards themselves. Confirm the current requirements applicable to your facility with the ESD Association or a qualified ESD programme manager.