A cleanroom flooring specification usually starts from the required resistance range and the grounding path, then works back to the sheet and the welding detail. Where a static control floor also has to stay cleanable under daily disinfection, welded homogeneous sheet is the lowest-risk build-up — there is no open seam for particles to collect in.
IEC 61340-5-1: The Governing Standard
| Classification | Resistance to ground (Rg) | Resistance point-to-point (Rp-p) | Typical application |
|---|---|---|---|
| Dissipative (ESD) | 10⁶ – 10⁹ Ω | 10⁶ – 10⁹ Ω | Electronics assembly, SMT lines, data centres |
| Conductive | < 10⁶ Ω | < 10⁶ Ω | Explosive / flammable environments (specialist) |
| Antistatic (static-dissipative) | 10⁹ – 10¹¹ Ω | — | Office environments; lighter ESD requirement |
IEC 61340-5-1:2024 (ed. 3) is the current edition. UNITECH NEXUS ESD vinyl sheet is designed to the dissipative range (10⁶ – 10⁹ Ω). Always confirm the specific resistance requirement with your EHS or facilities engineer before specifying.
Grounding System Requirements
- Copper grounding strips must be installed beneath the flooring as a grid (commonly 600 × 600 mm squares) and connected to the building earth.
- Use ESD-grade adhesive (antistatic formulation) — standard acrylic adhesives can insulate the floor from the grounding strips.
- U300D conductive adhesive (GREEN POINT) is compatible with UNITECH NEXUS ESD vinyl sheet.
- Resistance measurements should be taken after installation, when adhesive is fully cured (≥ 16 hours), before heavy equipment is placed.
- Ongoing testing: IEC 61340-5-1 recommends periodic resistance checks (at minimum annually) to confirm the floor continues to meet the specified resistance range.
Defining the Resistance Measurement Protocol Before Installation
Resistance measured on a finished floor is a system value. It is determined by the flooring sheet, the adhesive, the earthing network, the substrate and the measurement method — not by any single material. Agreeing the measurement protocol before installation prevents most of the disputes that otherwise arise after it.
Two measurements are involved and they are not interchangeable. Resistance to ground (Rg) is measured between an electrode on the floor and a known earth, and passes through the conductive layer, the earthing strips and the connection to the building earth. Point-to-point resistance (Rp-p) is measured between two electrodes on the floor surface and does not pass through the earthing network. A point-to-point reading can therefore still be low when the earthing network is incomplete or disconnected, so it cannot be used on its own to demonstrate compliance with a resistance-to-ground requirement.
The following should be agreed in writing before any measurement is taken:
- the standard applied;
- the electrode type and the load applied;
- the test voltage — for an electrode-to-earth measurement in the range 1 MΩ to 100 GΩ, the applicable test voltage is 100 V, while two-electrode surface and point-to-point measurements are taken at 10 V;
- the number and location of measurement points;
- the reported value, being the geometric mean of the measurements, and not the arithmetic mean or the worst single reading;
- the conditioning of the floor before measurement — a result may not be reliable if measured within 24 hours of laying or cleaning.
Earthing strip spacing is not prescribed by the standards. It is a design decision derived from the required resistance range, and should be agreed in writing before installation. Records worth keeping for later verification include the as-installed copper layout and its connection to the building earth, the installation specification followed, the adhesive consumption against the floor area covered, and the substrate type and moisture content reading taken before installation.
UNITECH NEXUS ESD Vinyl Sheet: Performance Data
| Parameter | Value | Standard | Notes |
|---|---|---|---|
| Resistance to ground (Rg) | 10⁶ – 10⁹ Ω | IEC 61340-5-1 | Measured over copper grounding grid |
| Resistance point-to-point (Rp-p) | 10⁶ – 10⁹ Ω | IEC 61340-5-1 | Dissipative classification |
| Surface layer thickness | 0.7 mm | EN ISO 10582 | Homogeneous construction |
| Total thickness | 2.0 mm | EN ISO 10582 | |
| Wear resistance | Group T | EN 660-2 | Verified by Intertek |
| Fire reaction | Class Bfl-s1 | EN 13501-1 | Intertek report 260709013SHF-006 |
| Welding rod compatibility | GP series (GREEN POINT) | ASTM F1516 | 4.0 mm welding rod; 3.5 mm groove max |
Clean Room Considerations
- Seam welding is mandatory in clean room installations — gaps and overlaps harbour particulates and disrupt ESD continuity.
- Surface finish: low-gloss or matt finish reduces light reflection in precision manufacturing environments.
- Chemical resistance: ESD vinyl sheet withstands IPA (isopropyl alcohol) cleaning, standard disinfectants and most laboratory chemicals at working concentrations.
- Clean room class compatibility: suitable for ISO Class 5–7 (Class 100–10,000) environments. For ISO Class 1–4, consult our technical team.
Frequently Asked Questions
What is the difference between ESD, antistatic and conductive flooring?
ESD (electrostatic dissipative) flooring has a resistance of 10⁶ – 10⁹ Ω and is specified under IEC 61340-5-1 for electronics and semiconductor environments. Antistatic flooring (10⁹ – 10¹¹ Ω) is a lighter requirement for offices and general circulation areas. Conductive flooring (< 10⁶ Ω) is used in explosive or flammable environments. UNITECH NEXUS ESD vinyl sheet is designed for the ESD (dissipative) range.
Does ESD flooring need a grounding system?
Yes. IEC 61340-5-1 requires the floor to be connected to earth ground via copper strips installed beneath the flooring. Without a grounding system, the floor cannot dissipate static charge regardless of its surface resistance. U300D conductive adhesive (GREEN POINT) must be used to maintain electrical continuity between the floor and the grounding strips.
What adhesive should be used with ESD flooring?
Standard acrylic adhesives are insulators and will break the electrical path between the floor and the grounding strips. A conductive adhesive such as U300D (GREEN POINT) must be used. U300D is formulated specifically for ESD vinyl sheet installation. Note that GP166 is a concrete primer, not an adhesive.
Can UNITECH NEXUS ESD vinyl be used in pharmaceutical clean rooms?
Yes. UNITECH NEXUS ESD vinyl sheet is compatible with ISO Class 5–7 clean room environments. It withstands IPA and standard pharmaceutical disinfectants. For ISO Class 1–4 environments, contact our technical team to confirm suitability for your specific contamination control protocol.
What is the minimum cure time before resistance testing?
Resistance measurements should be taken after the adhesive is fully cured — a minimum of 16 hours after installation at normal temperature and humidity. Testing before full cure can give artificially high resistance readings.