2027 ICD-10-CM Diagnosis Code T59.91XAToxic effect of unspecified gases, fumes and vapors, accidental (unintentional), initial encounter

ICD-10-CM Codes›S00–T88›T51-T65›T59

ICD-10-CM T59.91XA
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

T59.91XA is a billable ICD-10-CM diagnosis code for toxic effect of unspecified gases, fumes and vapors, accidental (unintentional), initial encounter. The 7th character A marks it as an initial encounter code, used while the patient is receiving active treatment. It is valid on HIPAA claims for fiscal year 2027 (October 1, 2026 through September 30, 2027) and groups to MS-DRG 917 through 918, 928 through 929, 934. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, accidental/unintentional; External cause codes: poisoning by non-drug; and Toxic effects, initial encounter.

Code Identity

ICD-10-CM Code
T59.91XA
Billable Status
Yes — Valid for Submission
Code Describes
Toxic effect of unspecified gases, fumes and vapors, accidental (unintentional), initial encounter
Short Description
Toxic effect of unsp gases, fumes and vapors, acc, init
Parent Code
T59.91
Toxic effect of unspecified gases, fumes and vapors, accidental (unintentional)

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT51-T65Toxic effects of substances chiefly nonmedicinal as to source
CategoryT59Toxic effect of other gases, fumes and vapors
This CodeT59.91XAToxic effect of unspecified gases, fumes and vapors, accidental (unintentional), initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Accidental poisoning by gaseous substance
  • Accidental poisoning by gases or fumes on ship
  • Accidental poisoning by gases or fumes on ship, docker or stevedore injured
  • Accidental poisoning by gases or fumes on ship, occupant of small powered boat injured
  • Accidental poisoning by gases or fumes on ship, occupant of small unpowered boat injured
  • Accidental poisoning by gases or fumes on ship, swimmer injured
  • Acute bronchiolitis
  • Acute bronchiolitis caused by chemical fumes
  • Acute bronchitis caused by chemical fumes
  • Acute edema
  • Acute pneumonitis caused by chemical fumes
  • Acute pulmonary alveolitis caused by chemical fumes
  • Acute pulmonary edema
  • Acute pulmonary edema caused by fume
  • Acute pulmonary edema caused by vapor
  • Asphyxiation by environmental toxic gas
  • Brass-founders' fever
  • Bronchitis and pneumonitis caused by chemical fumes
  • Bronchitis caused by chemical fumes
  • Bronchitis caused by vapor
  • Chronic bronchiolitis
  • Chronic emphysema caused by chemical fumes
  • Chronic emphysema caused by vapor
  • Chronic fibrosis of lung
  • Chronic obliterative bronchiolitis
  • Chronic obliterative bronchiolitis caused by chemical fumes
  • Chronic obliterative bronchiolitis caused by vapor
  • Chronic pulmonary fibrosis caused by vapor
  • Chronic respiratory condition caused by fumes
  • Chronic respiratory condition caused by vapor
  • Disorder due to vaping
  • Inflammation of upper respiratory tract caused by fumes
  • Inflammation of upper respiratory tract caused by vapor
  • Inhalation burn due to hot gas
  • Inhalation injury
  • Injury due to legal intervention by asphyxiation by gas
  • Injury due to legal intervention by gas
  • Injury due to legal intervention by poisoning by gas
  • Injury due to poison gas weapon
  • Interstitial pulmonary fibrosis due to inhalation of substance
  • Metal fever
  • Pneumonitis caused by fumes
  • Pneumonitis caused by vapor
  • Poisoning by fumes
  • Poisoning caused by gaseous substance
  • Poisoning due to crowd control gas
  • Poisoning due to irritant gas
  • Pulmonary edema caused by chemical fumes
  • Respiratory condition caused by chemical fumes
  • Respiratory condition caused by chemical fumes and vapor
  • Respiratory condition caused by vapor
  • Subacute obliterative bronchiolitis
  • Subacute obliterative bronchiolitis caused by chemical fumes
  • Subacute obliterative bronchiolitis caused by vapor
  • Toxic emphysema
  • Toxic inhalation injury
  • Toxic inhalation-induced febrile illness
  • Toxic pulmonary edema
  • War injury caused by gas
  • War injury due to fumes
  • War injury due to gases, fumes and chemicals

Coding GuidelinesGuidance

The appropriate 7th character is to be added to each code from block Toxic effect of other gases, fumes and vapors (T59). Use the following options for the applicable episode of care:

  • A - initial encounter
  • D - subsequent encounter
  • S - sequela

Source: ICD-10-CM Official Guidelines for Coding and Reporting, FY 2027, published by CMS and the National Center for Health Statistics.

Instructional NotesGuidance

Instructions from the official ICD-10-CM Tabular List that apply to T59.91XA: its own notes plus those printed at T59, block T51-T65, and Chapter 19. A note printed at a category, block or chapter applies to every code under it.

Includes

Further defines, or gives examples of, the content of the category.

From T59 Toxic effect of other gases, fumes and vapors applies to 144 codes
  • aerosol propellants

Excludes1

Not coded here: the excluded code is never reported together with this one, unless the two conditions are unrelated.

From T59 Toxic effect of other gases, fumes and vapors applies to 144 codes
  • chlorofluorocarbons (T53.5)
From Block T51-T65 Toxic effects of substances chiefly nonmedicinal as to source applies to 1,680 codes
  • contact with and (suspected) exposure to toxic substances (Z77.-)

Excludes2

Not included here: the excluded condition is not part of this code, but a patient may have both, so both codes may be reported.

From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Use Additional Code

Add a second code, after this one, to fully describe the condition.

From Block T51-T65 Toxic effects of substances chiefly nonmedicinal as to source applies to 1,680 codes
  • code(s):
  • for all associated manifestations of toxic effect, such as: respiratory conditions due to external agents (J60-J70)
  • personal history of foreign body fully removed (Z87.821)
  • to identify any retained foreign body, if applicable (Z18.-)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • code to identify any retained foreign body, if applicable (Z18.-)

Notes

General instructions on how these codes are used.

From Block T51-T65 Toxic effects of substances chiefly nonmedicinal as to source applies to 1,680 codes
  • When no intent is indicated code to accidental. Undetermined intent is only for use when there is specific documentation in the record that the intent of the toxic effect cannot be determined.
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes
  • Use secondary code(s) from Chapter 20, External causes of morbidity, to indicate cause of injury. Codes within the T section that include the external cause do not require an additional external cause code
  • The chapter uses the S-section for coding different types of injuries related to single body regions and the T-section to cover injuries to unspecified body regions as well as poisoning and certain other consequences of external causes.

7th Character

Every code in the category takes a 7th character from the listed values, with the placeholder X filling any empty positions before it.

From T59 Toxic effect of other gases, fumes and vapors applies to 144 codes
  • The appropriate 7th character is to be added to each code from category T59
Values for category T59 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter this code
  • Dsubsequent encounter
  • Ssequela

Source: CMS ICD-10-CM Tabular List. How to read instructional notes.

Referenced in Other NotesGuidance

Instructional notes printed at other codes that name T59.91XA, its category, or a range that includes it.

Excludes1 1

These codes carry an Excludes1 note naming T59.91XA: they are not reported together with it, unless the two conditions are unrelated.

  • T71 Asphyxiation
    asphyxia from other gases, fumes and vapors (T59.-) names T59.-, which includes this code

Clinical ClassificationClinical

AHRQ’s CCSR groups this code into broader clinical categories.

CCSR EXT020
External cause codes: intent of injury, accidental/unintentional
Default principal diagnosis: inpatient No · outpatient No
CCSR EXT015
External cause codes: poisoning by non-drug
Default principal diagnosis: inpatient No · outpatient No
CCSR INJ023
Toxic effects, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Table of Drugs and ChemicalsClinical

Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.

SubstanceAccidentalSelf-harmAssaultUndeter­minedAdverse
Effect		Under­dosing
Fumes (from)T59.91T59.92T59.93T59.94––
Gas NECT59.91T59.92T59.93T59.94––
Gas NEC::air contaminants, source or type not specifiedT59.91T59.92T59.93T59.94––
Gas NEC::nerve, not in warT59.91T59.92T59.93T59.94––
Gas NEC::sewerT59.91T59.92T59.93T59.94––
Gas NEC::specified source NECT59.91T59.92T59.93T59.94––
Lung irritant (gas) NECT59.91T59.92T59.93T59.94––
Mustard (emetic)::gas, not in warT59.91T59.92T59.93T59.94––
Nerve gas, not in warT59.91T59.92T59.93T59.94––
Sewer gasT59.91T59.92T59.93T59.94––
Vapor [See Also: Gas]T59.91T59.92T59.93T59.94––

Patient EducationClinical

Poisoning

A poison is any substance that is harmful to your body. You might swallow it, inhale it, inject it, or absorb it through your skin. Any substance can be poisonous if too much is taken. Poisons can include:

Read the full article at MedlinePlus

Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.

Convert T59.91XA to ICD-9-CMHistory

The closest ICD-9-CM equivalents under the General Equivalence Mappings.

ICD-9-CM
987.9 Toxic eff gas/vapor NOS
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.
ICD-9-CM
E869.8 Acc poison-gas/vapor NEC
ApproximateCombination The match is approximate, and more than one code can be needed to describe the source diagnosis. Confirm with contextual judgment.

Code HistoryHistory

FY 2016AddedAdded to the ICD-10-CM code setEffective October 1, 2015, the first year of ICD-10-CM.
FY 2017–2026No changes
FY 2027CurrentCurrent code set, no changesEffective October 1, 2026 through September 30, 2027.

Questions About T59.91XAOverview

Is T59.91XA a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of unspecified gases, fumes and vapors, accidental (unintentional), initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in T59.91XA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for toxic effect of unspecified gases, fumes and vapors, accidental (unintentional), such as an emergency visit or first evaluation.

What MS-DRG does T59.91XA group to?

When toxic effect of unspecified gases, fumes and vapors, accidental (unintentional), initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 918, 929, 934, 928, 917, with relative weights from 0.8716 to 7.6444 depending on complications. Higher weights mean higher Medicare reimbursement.

Can T59.91XA be reported with T53.5?

Not as a rule. The Excludes1 note at T59, which applies to T59.91XA, lists "chlorofluorocarbons (T53.5)". An Excludes1 note means the excluded code is never reported together with this one; the only exception is when the two conditions are unrelated to each other (Official Guidelines, Section I.A.12.a).

What is the ICD-9 equivalent of T59.91XA?

Under the General Equivalence Mappings, toxic effect of unspecified gases, fumes and vapors, accidental (unintentional), initial encounter converts to ICD-9-CM 987.9 (toxic eff gas/vapor NOS) and E869.8 (acc poison-gas/vapor NEC). The mapping is approximate, so confirm the match fits the documentation.