LOINCActiveObservation

LOINC Code 33471-4: Hydrogen/Expired gas post Unsp challenge (Exhl gas) [Volume fraction]

33471-4 is a LOINC code used to identify Hydrogen/Expired gas post Unsp challenge (Exhl gas) [Volume fraction] in laboratory and clinical observation data. You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges. LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Hydrogen/Expired gas^post XXX challenge. It is commonly used with the system or sample type Exhl gas.

Reviewed by HealthAssure Clinical TeamUpdated 21 May 2026

What is this code?

LOINC codes identify tests, measurements, observations, survey items, and clinical questions in a standardized way. It is associated with the component Hydrogen/Expired gas^post XXX challenge. It is commonly used with the system or sample type Exhl gas.

When is it used?

  • Used in lab systems, EHRs, and clinical data exchange.
  • May identify a test, observation, survey item, or clinical document request rather than a diagnosis.
  • Status: ACTIVE
  • Order vs observation: Observation

What it does not mean

  • The code identifies the observation or test, not the actual result.

Key facts

  • Hydrogen/Expired gas [Volume Fraction] in Exhaled gas --post XXX challenge
  • Hydrogen/Expired gas^post XXX challenge
  • After; Breath; CHEMISTRY.CHALLENGE TESTING; ExG; Exhaled gas; Exhaled gas (=breath); Gases; H2; Hyd; p chal; Percent; Point in time; PST; QNT; Quan; Quant; Quantitative; Random; Volfr; Volume fraction

Where you may see this code

You may see this code in lab systems, lab reports, EHR exports, interoperability feeds, or other structured clinical data exchanges.

Common synonyms

Hydrogen/Expired gas post Unsp challenge (Exhl gas) [Volume fraction]Hydrogen/Expired gas [Volume Fraction] in Exhaled gas --post XXX challengeBreath H2 p chalHydrogen/Expired gas^post XXX challengeCHALHydrogen/Expired Gas - after challenge, Exhaled gasVFr

Frequently asked questions

Code details

Code33471-4
SystemLOINC
Display nameHydrogen/Expired gas post Unsp challenge (Exhl gas) [Volume fraction]
DescriptionHydrogen/Expired gas^post XXX challenge
Short nameBreath H2 p chal
ComponentHydrogen/Expired gas^post XXX challenge
PropertyVFr
TimingPt
System (specimen)Exhl gas
ScaleQn
ClassCHAL
Example unitsppm
StatusACTIVE
Order/ObservationObservation

Flags

BillableNo
Valid clinical useNo

Source

SourceLOINC
Version2.82
Releasemain
First released2.09
Last changed2.73

Consumer names

Hydrogen/Expired Gas - after challenge, Exhaled gas

Part names

Hydrogen/Expired gas^post XXX challengeVFrPtExhl gasQnVolume FractionPoint in time (spot)Exhaled gas

About this content

This page is prepared by HealthAssure's clinical team using official coding standards from LOINC. AI tools assist with drafting explanations, which are then reviewed and verified by healthcare professionals for accuracy. This content is for informational purposes and does not replace professional medical advice. Meet our team.