FR vs
LSZH.
FR stands for Flame Retardant: PVC wire under IS 694:2010 with a flammability test, Oxygen Index ≥ 29% and Temperature Index ≥ 250°C, but no smoke or halogen limit. LSZH stands for Low Smoke Zero Halogen; its BIS designation is HFFR, Halogen-Free Flame Retardant, under IS 17048:2018 — a non-PVC polyolefin compound limited to 0.5% halogen acid gas, with light transmittance ≥ 70% through its smoke and Oxygen Index ≥ 31. They are different standards, different insulation chemistries, and separate BIS licences.
The two types — at a glance.
What each standard actually requires.
| Property | FR | LSZH / HFFR |
|---|---|---|
| Standard | IS 694:2010 | IS 17048:2018 |
| Insulation | PVC | Non-PVC polyolefin — no chlorine or bromine |
| Halogen acid gas | No limit in IS 694:2010 | ≤ 0.5% — IS 10810 (Part 59) |
| Combustion gas acidity | Not specified | pH ≥ 4.3, conductivity ≤ 10 µS/mm (Annex D) |
| Smoke | No limit in IS 694:2010 | Light transmittance ≥ 70% — IS 10810 (Part 63) |
| Oxygen Index | ≥ 29% | ≥ 31 |
| Temperature Index | ≥ 250°C | ≥ 250°C |
| Conductor temperature | 70°C | 70°C — thermoplastic (HFI-TP 70) |
| BIS licence | CM/L 8800140116 | CM/L 8800227819 |
Selection guidance.
FR wire is specified for general wiring where the project specification sets no smoke or halogen condition. LSZH/HFFR is specified where the project limits halogen acid gas to 0.5% — underground metro stations, data centres, and hospital tenders commonly carry that condition, because hydrogen chloride from burning PVC corrodes electronic equipment even at sub-ignition temperatures and impairs evacuation in enclosed spaces.
Specify by product — the National Cables range.
FR Single Core Wire — flame-retardant PVC, IS 694:2010, 0.5–240 mm². LSZH / HFFR Wire — halogen-free flame retardant, IS 17048:2018. All ranges use Class 5 conductors — strand construction and resistance limits: IEC 60228 / IS 8130:2013 conductor classes. Size selection for a given load: cable size calculator.
Related comparisons: FR vs FR-LSH · FR-LSH vs LSZH · full three-way comparison.
FR vs LSZH — selection questions.
Two different standards and insulation chemistries, and when each is the correct specification.
What is the difference between FR and LSZH wire?
FR is PVC wire under IS 694:2010 — flame retardant, but with no smoke or halogen limit. LSZH (BIS designation HFFR) is non-PVC polyolefin wire under IS 17048:2018 — halogen acid gas ≤ 0.5%, light transmittance ≥ 70%, Oxygen Index ≥ 31.
What is the full form of LSZH?
LSZH stands for Low Smoke Zero Halogen. It is also sold as FR-LSZH or FRLSZH (Flame Retardant Low Smoke Zero Halogen). The designation used by IS 17048:2018 is HFFR — Halogen-Free Flame Retardant.
Can FR and LSZH wire be interchanged?
No. They are made to different standards under separate BIS licences — CM/L 8800140116 (IS 694:2010) and CM/L 8800227819 (IS 17048:2018). FR has no smoke or halogen limit, so it does not meet a specification that names IS 17048:2018.
Why do metro stations and data centres specify LSZH rather than FR?
Burning PVC releases hydrogen chloride gas that corrodes electronic circuit boards, contacts, and metal infrastructure even at sub-ignition temperatures. LSZH/HFFR is limited to 0.5% halogen acid gas, protecting equipment during a fire elsewhere in the building. Underground metro stations carry the additional concern of evacuation in a confined space.
Is LSZH rated for a higher conductor temperature than FR?
Not in the National Cables range. IS 17048:2018 rates thermoplastic HFFR insulation (HFI-TP 70) at 70°C — the same conductor temperature as IS 694:2010 PVC. The 90°C rating applies only to crosslinked HFFR compounds, which are a different insulation grade.
Specify the correct cable for your project.
Our technical team matches IS 694:2010 and IS 17048:2018 cable types to your project specification.