2026 ICD-10-CM Diagnosis Code T58.2X4SToxic effect of carbon monoxide from incomplete combustion of other domestic fuels, undetermined, sequela
T58.2X4S is a billable ICD-10-CM diagnosis code for toxic effect of carbon monoxide from incomplete combustion of other domestic fuels, undetermined, sequela. The 7th character S marks it as a sequela code, which reports a problem that remains after the original condition has resolved. It is valid on HIPAA claims for fiscal year 2026 (October 1, 2025 through September 30, 2026) and groups to MS-DRG 922 through 923. The code is exempt from POA reporting. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Poisoning/toxic effect/adverse effects/underdosing, sequela.
Code Identity
Code Classification
Present on Admission (POA)Billing
T58.2X4S is exempt from POA reporting on inpatient claims to general acute care hospitals. Review other POA exempt codes.
Coding GuidelinesGuidance
The appropriate 7th character is to be added to each code from block Toxic effect of carbon monoxide (T58). 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
Substances in the Table of Drugs and Chemicals that reference this code family. Always confirm in the Tabular List before coding.
| Substance | Accidental | Self-harm | Assault | Undetermined | Adverse Effect | Underdosing |
|---|---|---|---|---|---|---|
| Coal (carbon monoxide from) [See Also: Carbon, monoxide, coal] | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Coal (carbon monoxide from) [See Also: Carbon, monoxide, coal]::oil | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Coal (carbon monoxide from) [See Also: Carbon, monoxide, coal]::tar | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Coal (carbon monoxide from) [See Also: Carbon, monoxide, coal]::tar::fumes | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Coal (carbon monoxide from) [See Also: Carbon, monoxide, coal]::tar::medicinal (ointment) | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Coal (carbon monoxide from) [See Also: Carbon, monoxide, coal]::tar::medicinal (ointment)::analgesics NEC | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Coal (carbon monoxide from) [See Also: Carbon, monoxide, coal]::tar::naphtha (solvent) | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Coke fumes or gas (carbon monoxide) | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Coke fumes or gas (carbon monoxide)::industrial use | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Furnace (coal burning) (domestic), gas from | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
| Furnace (coal burning) (domestic), gas from::industrial | T58.2X1 | T58.2X2 | T58.2X3 | T58.2X4 | – | – |
Patient EducationClinical
Carbon Monoxide Poisoning
Carbon monoxide (CO) is a gas that has no odor or color. But it is very dangerous. It can cause sudden illness and death. CO is found in combustion fumes, such as those made by cars and trucks, lanterns, stoves, gas ranges and heating systems. CO from these fumes can build up in places that don't have a good flow of fresh air.
Read the full article at MedlinePlus
Courtesy of MedlinePlus, a service of the U.S. National Library of Medicine.
Convert T58.2X4S to ICD-9-CMHistory
The closest ICD-9-CM equivalents under the General Equivalence Mappings.
Code HistoryHistory
Questions About T58.2X4SOverview
Is T58.2X4S a billable code?
Yes. This is a billable ICD-10-CM code, specific enough to report toxic effect of carbon monoxide from incomplete combustion of other domestic fuels, undetermined, sequela on HIPAA-covered claims from October 1, 2025 through September 30, 2026.
What does the 7th character S in T58.2X4S mean?
The final character S makes this a sequela code: it reports a lingering problem that remains after the toxic effect of carbon monoxide from incomplete combustion of other domestic fuels, undetermined itself has resolved, not the original event.
What MS-DRG does T58.2X4S group to?
When toxic effect of carbon monoxide from incomplete combustion of other domestic fuels, undetermined, sequela is the principal diagnosis on an inpatient stay, it groups to MS-DRG 922, 923, with relative weights from 1.0177 to 1.7494 depending on complications. Higher weights mean higher Medicare reimbursement.
Is T58.2X4S exempt from POA reporting?
Yes. CMS lists this code among those exempt from present on admission reporting, so hospitals do not assign a POA indicator for toxic effect of carbon monoxide from incomplete combustion of other domestic fuels, undetermined, sequela on inpatient claims.
What is the ICD-9 equivalent of T58.2X4S?
Under the General Equivalence Mappings, toxic effect of carbon monoxide from incomplete combustion of other domestic fuels, undetermined, sequela converts to ICD-9-CM 909.1 (late eff nonmed substanc). 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.
