2026 ICD-10-CM Diagnosis Code T59.814AToxic effect of smoke, undetermined, initial encounter
T59.814A is a billable ICD-10-CM diagnosis code for toxic effect of smoke, undetermined, 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 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 917 through 918, 928 through 929. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under External cause codes: intent of injury, undetermined; External cause codes: poisoning by non-drug; and Toxic effects, initial encounter.
Code Identity
Code Classification
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 2026, published by CMS and the National Center for Health Statistics.
Clinical ClassificationClinical
AHRQ’s CCSR groups this code into broader clinical categories.
Table of Drugs and ChemicalsClinical
Patient EducationClinical
Inhalation Injuries
Inhalation injuries are acute injuries to your respiratory system and lungs. They can happen if you breathe in toxic substances, such as smoke (from fires), chemicals, particle pollution, and gases. Inhalation injuries can also be caused by extreme heat; these are a type of thermal injuries.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T59.814A to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T59.814AOverview
Is T59.814A (Toxic effect of smoke, undetermined) a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of smoke, undetermined, initial encounter on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character A in T59.814A mean?
The final character A marks the initial encounter: use it while the patient is receiving active treatment for toxic effect of smoke, undetermined, such as an emergency visit or first evaluation.
What MS-DRG does T59.814A group to?
When toxic effect of smoke, undetermined, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 917, 918, 928, 929, with relative weights from 0.8571 to 7.1727 depending on complications. Higher weights mean higher Medicare reimbursement.
What is the ICD-9 equivalent of T59.814A?
Under the General Equivalence Mappings, toxic effect of smoke, undetermined, initial encounter converts to ICD-9-CM 987.9 (toxic eff gas/vapor NOS) and E982.8 (undet pois-gas/vapor NEC). The mapping is approximate, so confirm the match fits the documentation.
Footnotes
[1] Not chronic - A diagnosis code that does not fit the criteria for chronic condition (duration, ongoing medical treatment, and limitations) is considered not chronic. Some codes designated as not chronic are acute conditions. Other diagnosis codes that indicate a possible chronic condition, but for which the duration of the illness is not specified in the code description (i.e., we do not know the condition has lasted 12 months or longer) also are considered not chronic.
