Technical Guide
FRP Grating Fire Performance Guide
Fire is the first technical objection to FRP in any specification meeting — and the answer is data, not adjectives. This guide explains what each major test measures, what the resin systems achieve, and where each rating is actually required.
What the tests measure
| Test | What it measures | Where it matters |
|---|---|---|
| ASTM E84 (25 ft tunnel) | Flame spread index (FSI) and smoke developed index (SDI) on the specimen surface | US-market buildings, offshore, industrial specs |
| EN 13501-1 | Euroclass (E, D, C, B...) from SBI test plus dripping | EU public and commercial works |
| IMO FTP Code Part 2/5 | Surface flammability and smoke for marine use | Ships and offshore accommodation |
| ISO 3745-style smoke toxicity | Toxic gas species in combustion | Tunnels, offshore escape routes, naval |
What each resin achieves (typical)
| Resin system | ASTM E84 FSI | Typical SDI | EN 13501-1 | Typical use |
|---|---|---|---|---|
| Ortho / ISO polyester (standard) | FSI > 25 (often 60–150) | High | Class E–D | Dry industrial interiors |
| ISO with FR additives | ~25–50 | Moderate | D–C | Specs needing “FR” polyester |
| Vinyl ester (fire-retardant grade) | ≤ 25 (Class 1) | 450–750 | C–B | Process plants, US specs |
| Phenolic | ≤ 25 (Class 1) | 10–50 (lowest) | B | Offshore, tunnels, marine escape |
Values are typical industry figures for grating products; certificates are issued per production batch for project use. Confirm the exact rating and certificate at quotation.
Reading an ASTM E84 clause correctly
A spec that says “ASTM E84 Class 1” means FSI ≤ 25 — but says nothing about smoke. Two common traps:
- Smoke limit missing: vinyl ester achieves Class 1 flame spread but its SDI is far higher than phenolic's. Escape-route specs should carry an SDI limit (commonly ≤ 450, or much lower offshore).
- Certified vs typical data: insist on the certificate for the delivered batch, not a brochure figure from a different resin and thickness.
Where fire performance is genuinely required
- Offshore platforms: escape routes and accommodation-adjacent areas — phenolic is the default, with IMO and smoke-toxicity documentation
- Tunnels: smoke toxicity drives the choice toward phenolic regardless of FSI
- US industrial specs: Class 1 FSI commonly required in process areas — fire-retardant vinyl ester is the economical answer
- Dry interiors: standard polyester is usually acceptable — do not pay phenolic prices where the code does not demand it