--- title: "OM4 and LSZH Do Not Specify the Same Cable Property: Read Fire-Class Fields Separately" description: "Leviathan Systems — Technical content Published 2026-10-20; updated 2026-10-20." canonical: "https://www.leviathansystems.co/articles/fiber-cable-fire-classification-vs-optical-category" last-updated: "2026-10-20" --- # OM4 and LSZH Do Not Specify the Same Cable Property: Read Fire-Class Fields Separately Leviathan Systems — Technical content Published 2026-10-20; updated 2026-10-20. An OM4 LSZH description does not establish a complete finished-cable fire classification. OM4 identifies the optical fiber category; LSZH describes low-smoke, zero-halogen characteristics. Read the separately declared fire-performance, smoke, flaming-droplet and acidity fields for the exact cable. Then connect that evidence to the offered product and the requirements for its intended site use. ## Separate the fiber from the finished cable A buyer comparing two OM4 LSZH offers has two useful pieces of information, but an incomplete material comparison. OM4 identifies an optical fiber category. LSZH expands to low smoke zero halogen; the CommScope entries place it in Environmental Space. The full reaction-to-fire classification appears in additional fields. The distinction follows the property being assessed. Optical performance concerns transmission through the fiber. Reaction to fire concerns cable behavior during fire exposure, including heat release and flame propagation, with supplementary smoke, flaming-droplet and acidity properties. An optical-loss result cannot establish those burning characteristics. Matching OM4 therefore leaves a separate finished-cable question to resolve. References: [CS1](https://www.commscope.com/product-type/cables/fiber-cables/indoor-cables/item760241769/), [CS2](https://www.commscope.com/product-type/cables/fiber-cables/indoor-cables/item760250691/), [C1](https://www.corning.com/optical-communications/emea/en/home/support/products-certification-center/construction-products-regulation/cpr-frequently-asked-questions.html) ## Read every component of the reaction-to-fire class Read B2ca / s1a / d1 / a1 as four fields kept together. B2ca is the main fire-performance classification in the cited entry; s1a is its smoke classification, d1 its flaming-droplet classification and a1 its acidity classification. Corning's fire-property explanation distinguishes heat release and flame propagation from these supplementary properties. Keeping only B2ca discards information. Reducing s1a to s1 also changes the recorded description. A difference between d0 and d1 belongs to the droplet field; it says nothing about whether the fiber is a better optical grade. Preserve the exact reported components before asking whether the offered product satisfies the applicable requirement. References: [CS1](https://www.commscope.com/product-type/cables/fiber-cables/indoor-cables/item760241769/), [CS2](https://www.commscope.com/product-type/cables/fiber-cables/indoor-cables/item760250691/), [C1](https://www.corning.com/optical-communications/emea/en/home/support/products-certification-center/construction-products-regulation/cpr-frequently-asked-questions.html) ## Two manufacturer entries show what the shorthand omits CommScope item 760241769, N-024-DS-5K-FSUAQ/B2, is described as a distribution cable. Its optical field lists OM4. Its environmental fields separately list LSZH and Riser, with fire performance B2ca, smoke s1a, droplets d1 and acidity a1. Item 760250691, N-024-MP-5K-F12AQ/20T/B2, is described as an MPO trunk cable. It also lists OM4 and LSZH, while its corresponding fire fields are B2ca, s1a, d0 and a1. OFNR and FT4 appear separately in its Environmental Space entry. These are different cable constructions, not a proposed replacement pair. Their shared OM4 and LSZH descriptions do not predict the full fire-class fields. Even the shared /B2 ending in the product names leaves the different droplet entries undisclosed. Read the actual fields rather than reconstructing the whole class from a product-code fragment. The additional OFNR and FT4 entries supply no cross-system equivalence or permission rule. References: [CS1](https://www.commscope.com/product-type/cables/fiber-cables/indoor-cables/item760241769/), [CS2](https://www.commscope.com/product-type/cables/fiber-cables/indoor-cables/item760250691/) ## Worked example: two offers both say OM4 LSZH Consider a fictional request for an OM4 cable offer that must identify the finished part and its complete declared reaction-to-fire class. All offer, part and document identifiers below are invented; the request sets no legal minimum. Offer A says OM4 LSZH, identifies finished part EX-CAB-A and references declaration EX-DOP-A, issue 2, reporting B2ca / s1a / d1 / a1. Offer B says OM4 LSZH indoor cable and provides a family brochure without an exact finished-part or declaration reference. Both offers state the requested fiber category. A provides a traceable claim for documentary review. B has not yet established which finished product and declared class the buyer would be comparing. That missing evidence does not demonstrate a failed fire test or an unsuitable product; it identifies the information still needed. A useful return to B is: identify the exact finished cable, provide its applicable declaration reference and issue, and state all fire-performance, smoke, droplet and acidity components. Review A's document against its part identity as well. More detailed wording makes an offer assessable; it does not by itself establish that the cable is permitted on the intended route. ## Join the part, declaration and site requirement A catalog page is a manufacturer's product statement. A Declaration of Performance, or DoP, provides the declared-performance document to examine for the identified product. The supplied-item identity connects the material offered or delivered to that documentary record. Keep those relationships visible instead of treating a family brochure as evidence for every variant. For a useful comparison record, retain the exact offered part, the declaration identifier and applicable issue, the product coverage stated in that document, the complete class and the source retrieval date. Where a declaration covers a family, establish how the offered variant falls within that coverage. Ask the issuer or appointed supplier to clarify an unresolved link. These are comparison fields, not a claim that every declaration uses an identical format. The first CommScope page says a DoP is available. That availability statement does not verify the declaration's contents or any delivered cable; neither has been examined for this article. Site use is another determination. The European Commission distinguishes the common framework for placing construction products on the EU market from national rules governing their use and installation. Its overview also describes a transition between frameworks by product family. An old regulatory summary or a catalog label cannot settle the current requirements for a particular building and route. Obtain the applicable project requirement and its responsible qualified decision owner. References: [CS1](https://www.commscope.com/product-type/cables/fiber-cables/indoor-cables/item760241769/), [E1](https://single-market-economy.ec.europa.eu/sectors/construction/construction-products-regulation-cpr/cpr-overview_en) ## A substitution can retain OM4 while changing the fire evidence Continue the fictional comparison: B now identifies EX-CAB-B and supplies a declaration reporting B2ca / s1a / d0 / a1. The missing declaration has become a specific product and classification comparison. The OM4 description remains unchanged, while the droplet component differs from A's claim. Record the two exact products, their complete classes and the document issues. Ask the responsible owner to determine the significance of the difference against the actual requirement. Do not silently rewrite both records as B2ca, rank optical performance from d0 versus d1, or infer that the shared LSZH wording authorizes the change. The optical application and the physical installation still need their own comparison. A changed construction can raise separate route, entry or termination questions. Keep the resulting decisions tied to the affected product and intended use, so a narrow response to the fire-property question does not become blanket interchangeability. ## Bring the comparison into the physical cabling scope For a physical installation discussion, prepare the exact cable identifiers, applicable product documents, intended routes and endpoints, material-supply responsibilities and unresolved selection questions. Carry the agreed product identity into the cable schedule and material record rather than shortening it back to OM4 LSZH. Leviathan's structured cabling service covers agreed physical installation, routing, identification and handoff. Physical planning and CAD documentation can be discussed where the package needs coordination, with authoring capability, reviewer and outputs confirmed for the engagement. Product selection and site fire-use decisions require their appointed owners. Use the linked service scope and project inquiry to describe the installation or documentation work needed; a material comparison does not create a supply commitment, product certification or work approval. ## Primary sources - [CS1 — CommScope 760241769 — N-024-DS-5K-FSUAQ/B2](https://www.commscope.com/product-type/cables/fiber-cables/indoor-cables/item760241769/). Checked 2026-10-20. Named product fields and DoP availability only; no declaration or delivered material examined. - [CS2 — CommScope 760250691 — N-024-MP-5K-F12AQ/20T/B2](https://www.commscope.com/product-type/cables/fiber-cables/indoor-cables/item760250691/). Checked 2026-10-20. Named product fields only; no international rating equivalence or cable interchangeability inferred. - [C1 — Corning CPR FAQ — fire-property terminology in questions 7–8](https://www.corning.com/optical-communications/emea/en/home/support/products-certification-center/construction-products-regulation/cpr-frequently-asked-questions.html). Checked 2026-10-20. Older FAQ used only for heat/flame, smoke, flaming-droplet and acidity terminology. Its regulatory dates, exemptions and national examples are not used. - [E1 — European Commission — Construction Products Regulation Overview](https://single-market-economy.ec.europa.eu/sectors/construction/construction-products-regulation-cpr/cpr-overview_en). Checked 2026-10-20. Market framework versus national use/installation rules and product-family transition only. No migration date, universal declaration obligation or site-specific minimum inferred. ## Related Leviathan resources - [OM4, OM5 and OS2: What the Fiber Label Tells You](/articles/om4-vs-om5-vs-os2-fiber-selection) - [Armored Fiber in Data Halls: Separate Construction from Cable Rating](/articles/armored-vs-standard-fiber-data-hall) - [Structured Cabling QA: Separate Inspection, Measurement and Acceptance](/articles/structured-cabling-qa-gpu-racks) - [Structured cabling and fiber installation](/services/structured-cabling) - [Physical infrastructure planning and CAD](/services/engineering-design) ## Define the cable package and open material questions Share a nonconfidential outline of the cable scope, part and declaration questions, intended routes, supply responsibilities and required installation or documentation outputs. [Discuss the scope](/contact?service=structured-cabling&from=/articles/fiber-cable-fire-classification-vs-optical-category)