The STZ (Sterilization Parameter) segment was introduced in HL7 v2.7 as part of the sterilization messaging suite. It carries the four coded parameters that define how a cycle is being run or how a device is being maintained: the sterilization type (steam, EtO, hydrogen peroxide vapor, etc.), the sterilization cycle (prevac, gravity, flash, etc.), the maintenance cycle, and the maintenance type. STZ is the parameter sheet that pairs with the cycle event in SDD and the lot manifest in SLT.
Purpose
STZ answers "what kind of sterilization was performed and what maintenance regime applies?" The four CWE fields let receivers categorize cycles by modality, validate that the right cycle type was used for the lot's contents, and schedule maintenance based on the device's recorded maintenance cycle/type. Without STZ, downstream systems know that a cycle ran but cannot judge whether it was the appropriate process.
Used in
STZ is most commonly seen in lab automation and sterilization cycle messages:
- ESU — Equipment Status Update — primary carrier; STZ accompanies SDD/SLT in cycle-complete updates.
- ESR — Equipment Status Request — used when a manager asks a device which parameters are configured for the current load.
- Sterilization cycle messages grouping SCP, SDD, SLT, and STZ for the full cycle record.
Field-by-field reference
Source: HAPI HL7v2 v2.8.1 javadocs (https://hapifhir.github.io/hapi-hl7v2/v281/apidocs/ca/uhn/hl7v2/model/v281/segment/STZ.html). Length —; Required and Table # from the HL7 v2 standard where well-established.
| Seq | Name | Data Type | Length | Req | Repeat | Table # | Description |
|---|---|---|---|---|---|---|---|
| STZ-1 | Sterilization Type | cwe | — | R | — | — | Coded modality of sterilization. |
| STZ-2 | Sterilization Cycle | cwe | — | O | — | — | Coded cycle name for the device. |
| STZ-3 | Maintenance Cycle | cwe | — | O | — | — | Coded maintenance schedule applied. |
| STZ-4 | Maintenance Type | cwe | — | O | — | — | Coded type of maintenance performed. |
Most-used fields
- STZ-1 Sterilization Type — the primary identifier; receivers route on modality (steam vs. EtO vs. plasma) and treat this as required in practice.
- STZ-2 Sterilization Cycle — disambiguates within a modality (prevac vs. gravity vs. flash steam cycles). Necessary for instrument-compatibility checks.
- STZ-3 Maintenance Cycle — used by asset management dashboards to track whether scheduled maintenance windows have been observed.
- STZ-4 Maintenance Type — distinguishes preventive maintenance from corrective; used in regulatory reporting.
Version differences (2.6 to 2.8.2)
- 2.6 — STZ did not exist; sterilization parameters were sent as free text in NTE or as vendor Z-segments.
- 2.7 — STZ introduced with the four CWE fields shown above.
- 2.8 — No structural changes. Industry continued to converge on shared vocabulary for STZ-1 and STZ-2.
- 2.8.1 — Documented here; identical field set to 2.8 with refined CWE coding guidance.
- 2.8.2 — No new fields; clarifications on the relationship between STZ-3 Maintenance Cycle and asset management workflows.
Common mistakes
- Sending STZ without STZ-1 Sterilization Type — receivers cannot categorize the cycle and typically discard the segment.
- Using local free-text values in STZ-1 rather than coded CWE; downstream modality routing breaks.
- Conflating STZ-2 Sterilization Cycle with STZ-3 Maintenance Cycle. STZ-2 is about the load being processed; STZ-3 is about device upkeep schedules.
- Sending STZ with maintenance fields populated but SDD-4 Device Data State set to a cycle state — receivers cannot tell whether the message is a cycle record or a maintenance record.
- Repeating STZ segments under one SDD to represent multi-phase cycles; emit one STZ per SDD and use SDD-4 to describe phase.
- Sending STZ to a v2.5.1 receiver — the segment did not exist before v2.7.
Examples
Minimal STZ:
STZ|STEAM^Steam^HL70806
Fully-populated STZ:
STZ|STEAM^Steam^HL70806|PREVAC^Pre-vacuum^HL70702|MONTHLY^Monthly^HL70809|PM^Preventive Maintenance^HL70811
Annotated breakdown:
STZ segment id
|STEAM^Steam^HL70806 STZ-1 Sterilization Type (CWE)
|PREVAC^Pre-vacuum^HL70702 STZ-2 Sterilization Cycle (CWE)
|MONTHLY^Monthly^HL70809 STZ-3 Maintenance Cycle (CWE)
|PM^Preventive Maintenance^HL70811 STZ-4 Maintenance Type (CWE)
In-context ESU excerpt (cycle-complete with parameters):
MSH|^~&|STERILECTRL|CSSD|LIS|LAB|20260610094500||ESU^U01^ESU_U01|MSG00001906|P|2.8.1
EQU|STZ-AUTOCLAVE-07^^STERILE-CENTRAL^EI|20260610094500|IDLE^Idle^HL70569
SCP|1|HOURS^Hours^HL70718|YYYYMMDDHHMM^Long^HL70529|STZ-AUTOCLAVE-07^^STERILE-CENTRAL^EI|Central OR Autoclave 7|MedSteam 5000XL|STEAM^Steam Autoclave^HL70667|Y^Lot Controlled^HL70136
SDD|LOT-20260610-014^^STERILE-CENTRAL^EI|STZ-AUTOCLAVE-07^^STERILE-CENTRAL^EI|Central OR Autoclave 7|COMPLETE^Cycle Complete^HL70667|UNLOADED^Unloaded^HL70669|200|Jordan Pierce
SLT|STZ-AUTOCLAVE-07^^STERILE-CENTRAL^EI|Central OR Autoclave 7|LOT-20260610-014^^STERILE-CENTRAL^EI|TRAY-ORTHO-118^^CSSD-INV^EI|*TRAY-ORTHO-118*20260610*
STZ|STEAM^Steam^HL70806|PREVAC^Pre-vacuum^HL70702|MONTHLY^Monthly^HL70809|PM^Preventive Maintenance^HL70811
In-context ESU excerpt (low-temperature plasma cycle for heat-sensitive instruments):
MSH|^~&|STERILECTRL|CSSD|LIS|LAB|20260610114000||ESU^U01^ESU_U01|MSG00001918|P|2.8.1
EQU|STZ-PLASMA-02^^STERILE-CENTRAL^EI|20260610114000|IDLE^Idle^HL70569
SCP|1|MIN^Minutes^HL70718|YYYYMMDDHHMM^Long^HL70529|STZ-PLASMA-02^^STERILE-CENTRAL^EI|Endo Plasma 2|VaporPro HP-300|H2O2-PLASMA^Hydrogen Peroxide Plasma^HL70667|Y^Lot Controlled^HL70136
SDD|LOT-20260610-031^^STERILE-CENTRAL^EI|STZ-PLASMA-02^^STERILE-CENTRAL^EI|Endo Plasma 2|COMPLETE^Cycle Complete^HL70667|UNLOADED^Unloaded^HL70669|200|Sasha Reid
SLT|STZ-PLASMA-02^^STERILE-CENTRAL^EI|Endo Plasma 2|LOT-20260610-031^^STERILE-CENTRAL^EI|SCOPE-ENDO-552^^CSSD-INV^EI|*SCOPE-ENDO-552*20260610*
STZ|H2O2-PLASMA^Hydrogen Peroxide Plasma^HL70806|STANDARD^Standard^HL70702|QUARTERLY^Quarterly^HL70809|PM^Preventive Maintenance^HL70811
See the ESU message page for the full trigger event and segment grouping.
FHIR mapping
No segment-level ConceptMap is published in the v2-to-FHIR IG for STZ. Conceptually, STZ-1 Sterilization Type and STZ-2 Sterilization Cycle map to a Procedure.code plus a category on a sterilization-event resource, or to Observation components describing the cycle modality and recipe. STZ-3 Maintenance Cycle and STZ-4 Maintenance Type map to Device.property or to a maintenance-event resource referencing the Device. Sterilization data overall maps conceptually to FHIR Device, DeviceMetric, and Substance resources rather than a one-to-one segment mapping.
Engine considerations
- Validate that STZ-1 Sterilization Type is present and uses a value from your governed CWE table; reject the segment otherwise.
- Maintain the SDD/SLT/STZ group integrity. STZ is meaningful only in relation to the cycle event it accompanies.
- If your engine performs instrument-compatibility checks, build them on (STZ-1, STZ-2) — modality plus cycle. STZ-1 alone is not enough to flag, for example, a flash cycle on an implant.
- STZ-3 and STZ-4 should be left empty for routine production cycles; populating them signals a maintenance event and routes differently downstream.
- Use a single STZ per SDD; if vendors emit multiple, normalize to one and capture the additional parameters in NTE.
- For receivers still on v2.5.1, transform STZ to NTE or Z-segments; the segment did not exist before v2.7.
How Vorro parses and produces STZ
Vorro treats STZ as the cycle parameter sheet. On inbound: STZ is joined to the preceding SDD via segment-group position, and the (STZ-1, STZ-2) pair is normalized against Vorro's curated sterilization-modality vocabulary so downstream analytics can group cycles regardless of vendor coding drift. When STZ-3 or STZ-4 are populated, Vorro raises a maintenance-event record alongside the cycle event. On outbound: Vorro generates STZ from the cycle's stored modality and recipe, populating STZ-1 from the device's configured modality and STZ-2 from the recipe library; maintenance fields are emitted only when the source event is a maintenance event, never on production cycles. Vorro rejects outbound messages where STZ-1 is empty or where STZ-1 conflicts with the device type on the matching SCP.
