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T59.821 ICD-10-CM Code: Toxic effect of hexamethylene diisocyanate, accidental (unintentional)

Billing Status: NO. This is a clinician non-billable / parent hierarchy grouping in the ICD-10-CM system.

Code Set: New for FY2027 — not valid before October 1, 2026.

Code Overview

No additional overview provided for this record.

Official Tabular Instructional Notes

Sequencing, inclusion, and exclusion notes published for T59.821 in the official ICD-10-CM tabular list.

Includes

Conditions the official ICD-10-CM tabular list includes under this code.

  • aerosol propellants inherited from T59

Inclusion Terms

Alternative terms the tabular list files under this code.

  • Toxic effects of hexamethylene diisocyanate NOS

Excludes1 — Not Coded Here

Conditions generally not reported together with this code (Excludes1) -- an error unless the two conditions are documented as unrelated to each other (ICD-10-CM Official Guidelines, Section I.A.12.a).

Use Additional Code

Supplementary codes the tabular list directs you to add.

  • Use additional code(s): inherited from T51-T65
  • for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70) inherited from T51-T65
  • personal history of foreign body fully removed (Z87.821) inherited from T51-T65
  • to identify any retained foreign body, if applicable (Z18.-) inherited from T51-T65

Frequently Compared Codes

The official Excludes notes on T59.821 name these codes. Each comparison page covers when the two can — or must not — be reported together.

Change history

  • Upcoming · effective FY2027 — 2026-10-01
    Will be added to the code set
    Toxic effect of hexamethylene diisocyanate, accidental (unintentional)
    FY2027 changes

Verify Before Coding

From the code registry, the Medicare Code Editor, and the MS-DRG Definitions Manual. Check it against a full claim in Claim Check.

Relationships & Classification

Other codes that name T59.821 or its code family, from the CMS ICD-10-CM tabular instructional notes. Tabular-note edges are stored at the code family level that carries each note.

Referenced by 1 Excludes1 note: T71 (via T59.-).

These codes’ tabular lists mark this diagnosis as mutually exclusive — not reported together unless the conditions are documented as unrelated.

Contextual Map

Every relationship of T59.821 in one view: hierarchy, official tabular instructions in both directions, clinical classification, risk adjustment, MS-DRG participation, index terms and change history — each edge carrying the CMS source it derives from.

Hierarchy

  • S00-T88 — Chapter 19: Injury, Poisoning and Certain Other Consequences of External Causes (S00-T88) (S00-T88) [Hierarchy]
  • T51-T65 — Toxic effects of substances chiefly nonmedicinal as to source [Hierarchy]

Referenced by Excludes1 notes

  • T71 — Asphyxiation [Excludes1](via T59.-): “asphyxia from other gases, fumes and vapors (T59.-)” · check together

Nearest codes (40)

  • T59 — Toxic effect of other gases, fumes and vapors [Sibling]
  • T59.7X4S — Toxic effect of carbon dioxide, undetermined, sequela [Sibling]
  • T59.8 — Toxic effect of other specified gases, fumes and vapors [Sibling]
  • T59.81 — Toxic effect of smoke [Sibling]
  • T59.811 — Toxic effect of smoke, accidental (unintentional) [Sibling]
  • T59.811A — Toxic effect of smoke, accidental (unintentional), initial encounter [Sibling]
  • T59.811D — Toxic effect of smoke, accidental (unintentional), subsequent encounter [Sibling]
  • T59.811S — Toxic effect of smoke, accidental (unintentional), sequela [Sibling]
  • and 32 more

Change history

  • FY2027 — Will be added to the code set [Change history]

Frequently Asked Questions (FAQ) & Clinical Guidance

Can T59.821 be billed directly?

No. T59.821 (Toxic effect of hexamethylene diisocyanate, accidental (unintentional)) is a non-billable ICD-10-CM category code. A more specific billable subcode must be selected based on clinical documentation.

Does T59.821 require a 7th character?

Yes. The appropriate 7th character is to be added to each code from category T59.

Nearest Codes in This Family

Official ICD-10-CM classifications closest to T59.821 in its code family, with their registry titles.

  • T59.814 — Toxic effect of smoke, undetermined
  • T59.814A — Toxic effect of smoke, undetermined, initial encounter
  • T59.814D — Toxic effect of smoke, undetermined, subsequent encounter
  • T59.814S — Toxic effect of smoke, undetermined, sequela
  • T59.82 — Toxic effects of hexamethylene diisocyanate
  • T59.821A — Toxic effect of hexamethylene diisocyanate, accidental (unintentional), initial encounter
  • T59.821D — Toxic effect of hexamethylene diisocyanate, accidental (unintentional), subsequent encounter
  • T59.821S — Toxic effect of hexamethylene diisocyanate, accidental (unintentional), sequela
  • T59.822 — Toxic effect of hexamethylene diisocyanate, intentional self-harm
  • T59.822A — Toxic effect of hexamethylene diisocyanate, intentional self-harm, initial encounter

View all codes in the T59 family