2027 ICD-10-CM Diagnosis Code T27.7XXACorrosion of respiratory tract, part unspecified, initial encounter

ICD-10-CM Codes›S00–T88›T26-T28›T27

ICD-10-CM T27.7XXA
CMSSource: CMS FY 2027 ICD-10-CM dataset · Effective Oct 1, 2026 – Sep 30, 2027

T27.7XXA is a billable ICD-10-CM diagnosis code for corrosion of respiratory tract, part unspecified, 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 205 through 206, 928 through 929, 934. As a secondary diagnosis, it counts as a complication or comorbidity (CC) and moves an inpatient stay to a higher severity level within its MS-DRG family. It does not count, however, when the principal diagnosis is one of 20 closely related codes. Coders also document this condition as chemical burn of respiratory tract. In AHRQ's Clinical Classifications Software (CCSR), this diagnosis falls under Burn and corrosion, initial encounter.

Code Identity

ICD-10-CM Code
T27.7XXA
Billable Status
Yes — Valid for Submission
Code Describes
Corrosion of respiratory tract, part unspecified, initial encounter
Short Description
Corrosion of respiratory tract, part unsp, init encntr
Parent Code
T27.7
Corrosion of respiratory tract, part unspecified

Code Classification

ChapterS00–T88Injury, poisoning and certain other consequences of external causes
SectionT26-T28Burns and corrosions confined to eye and internal organs
CategoryT27Burn and corrosion of respiratory tract
This CodeT27.7XXACorrosion of respiratory tract, part unspecified, initial encounter

Approximate SynonymsGuidance

Alternate terms and clinical phrases that map to this code.

  • Chemical burn of respiratory tract

Coding GuidelinesGuidance

The ICD-10-CM makes a distinction between burns and corrosions. The burn codes are for thermal burns, except sunburns, that come from a heat source, such as a fire or hot appliance. The burn codes are also for burns resulting from electricity and radiation. Corrosions are burns due to chemicals. The guidelines are the same for burns and corrosions.

Sequence first the code that reflects the highest degree of burn when more than one burn is present.

  • When the reason for the admission or encounter is for treatment of external multiple burns, sequence first the code that reflects the burn of the highest degree.
  • When a patient has both internal and external burns, the circumstances of admission govern the selection of the principal diagnosis or first-listed diagnosis.
  • When a patient is admitted for burn injuries and other related conditions such as smoke inhalation and/or respiratory failure, the circumstances of admission govern the selection of the principal or first-listed diagnosis.

Burns of the eye and internal organs (T26-T28) are classified by site, but not by degree.

Classify burns of the same local site (three-character category level, T20-T28) but of different degrees to the subcategory identifying the highest degree recorded in the diagnosis.

The appropriate 7th character is to be added to each code from block Burn and corrosion of respiratory tract (T27). 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 T27.7XXA: its own notes plus those printed at T27.7, T27, block T20-T32, 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 Block T20-T32 applies to 2,584 codes
  • burns (thermal) from electrical heating appliances
  • burns (thermal) from electricity
  • burns (thermal) from flame
  • burns (thermal) from friction
  • burns (thermal) from hot air and hot gases
  • burns (thermal) from hot objects
  • burns (thermal) from lightning
  • burns (thermal) from radiation
  • chemical burn [corrosion] (external) (internal)
  • scalds

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 Block T20-T32 applies to 2,584 codes
  • erythema [dermatitis] ab igne (L59.0)
  • radiation-related disorders of the skin and subcutaneous tissue (L55-L59)
  • sunburn (L55.-)
From Chapter 19 (S00-T88) Injury, poisoning and certain other consequences of external causes applies to 41,187 codes

Code First

The underlying condition named in the note is sequenced before this code.

From T27.7 Corrosion of respiratory tract, part unspecified applies to 3 codes
  • (T51-T65) to identify chemical and intent

Use Additional Code

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

From T27 Burn and corrosion of respiratory tract applies to 24 codes
  • external cause code to identify the source and intent of the burn (X00-X19, X75-X77, X96-X98)
  • external cause code to identify place (Y92)
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 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 T27 Burn and corrosion of respiratory tract applies to 24 codes
  • The appropriate 7th character is to be added to each code from category T27
Values for category T27 Encounter: Initial, Subsequent, Sequela
  • Ainitial encounter this code
  • Dsubsequent encounter
  • Ssequela

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

Clinical ClassificationClinical

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

CCSR INJ019
Burn and corrosion, initial encounter
Default principal diagnosis: inpatient Yes · outpatient Yes

Patient EducationClinical

Burns

A burn is damage to your body's tissues caused by heat, chemicals, electricity, sunlight, or radiation. Scalds from hot liquids and steam, building fires and flammable liquids and gases are the most common causes of burns. Another kind is an inhalation injury, caused by breathing smoke.

Read the full article at MedlinePlus

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

Convert T27.7XXA to ICD-9-CMHistory

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

ICD-9-CM
947.1 Burn larynx/trachea/lung
Approximate The match is approximate rather than exact.

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 T27.7XXAOverview

What is the ICD-10 code for corrosion of respiratory tract, part unspecified, initial encounter?

The ICD-10-CM code for corrosion of respiratory tract, part unspecified, initial encounter is T27.7XXA (sometimes written as T277XXA). It is billable on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

Is T27.7XXA (Corrosion of respiratory tract, part unspecified) a billable code?

Yes. This is a billable ICD-10-CM code, specific enough to report corrosion of respiratory tract, part unspecified, initial encounter on HIPAA-covered claims from October 1, 2026 through September 30, 2027.

What does the 7th character A in T27.7XXA mean?

The final character A marks the initial encounter: use it while the patient is receiving active treatment for corrosion of respiratory tract, part unspecified, such as an emergency visit or first evaluation.

What MS-DRG does T27.7XXA group to?

When corrosion of respiratory tract, part unspecified, initial encounter is the principal diagnosis on an inpatient stay, it groups to MS-DRG 206, 929, 205, 934, 928, with relative weights from 0.9255 to 7.6444 depending on complications. Higher weights mean higher Medicare reimbursement.

Is T27.7XXA a CC or MCC?

CMS lists T27.7XXA as a CC (complication or comorbidity) for FY 2027. Reported as a secondary diagnosis, it moves the inpatient stay to a higher-weighted DRG within its severity family. It does not count when the principal diagnosis is one of the 20 closely related codes in its exclusion list.