Depyrogenation tunnel and dry heat oven
Dry heat steriliser · Sterilising tunnel · Hot air tunnel · Depyrogenation oven
The continuous tunnel or batch oven that sterilises and depyrogenates glass with hot, HEPA-filtered air, validated by endotoxin reduction as well as heat.
What this page does not claim
An equipment family page teaches how a kind of equipment works and how it is assured. It is not a qualification of any site’s equipment, sets no universal limits, and was checked by SPEQ against the sources it lists, not by an independent engineer.
WHAT IT DOES
Dry heat uses hot air to sterilise and, at higher exposures, to destroy endotoxin, which moist heat does not remove. Annex 1 describes it as "of particular use in the thermal removal of difficult-to-eliminate thermally robust contaminants such as endotoxin/pyrogen" (8.66). A tunnel takes washed vials on a belt through heating, sterilising and cooling zones into grade A at the filling line.
Where heat is used to depyrogenate, validation shows a suitable Fh value and a minimum 3 log10 reduction in endotoxin; when that is achieved, sterilisation need not be shown separately (Annex 1, 8.68).
Where it sits: Between the vial washer and the filling line (tunnel), or in component preparation (oven).
WHERE YOU FIND IT
- Glass vials and ampoules before aseptic filling
- Glass and metal components and equipment
- Heat-stable starting materials
In the reference facility: Aseptic filling & isolator line, Equipment wash & parts preparation
Not covered on this page: Moist heat sterilisation; Endotoxin removal by rinsing or chemical means.
MAJOR COMPONENTS
- Infeed (washer side). Receives washed containers.
- Heating and sterilising zone. Brings containers to and holds them at the validated temperature.
- Cooling zone. Cools containers under grade A air before filling; cooling air that contacts sterilised material must itself be sterile (Annex 1, 8.53).
- HEPA filters on all supply air. At least HEPA, integrity tested at least twice a year (Annex 1, 8.67); all air entering an oven passes a HEPA filter (8.70).
- Belt and drive. Sets dwell time in the sterilising zone.
- Pressure balance dampers. Hold the pressure profile that protects the grade A sterilising zone (Annex 1, 8.67).
Connects to: Vial washer; Filling line in grade A; Cleanroom pressure cascade; Batch and cycle records.
INSTRUMENTS AND WHAT THEY MEASURE
- Temperature sensor (RTD or thermocouple). Zone temperatures and, in validation, heat penetration of containers. Watch for: sensor not at the location that matters (cold spot, load centre).
- Differential pressure transmitter. Pressure differences along the tunnel and to the rooms either side (Annex 1, 8.67). Watch for: ports connected the wrong way round, reversing the sign.
- Airflow velocity probe (anemometer). Air speed in the sterilising and cooling zones. Watch for: readings taken at a different height from the one qualified.
- Optical particle counter. Air quality in the cooling zone and at the exit to grade A. Watch for: sample tubing long or bent enough to lose large particles.
- Endotoxin challenge containers. Endotoxin log reduction in validation (Annex 1, 8.68, 8.69). Watch for: spiked containers not fully reconciled (annex 1, 8.69).
PARAMETERS
SETPOINT · MEASURED · LIMIT · ATTRIBUTE- Temperature (limit, °C). Minimum and maximum in the sterilising zone, as the site defined them in validation (Annex 1, 8.67).
- Belt speed or dwell time (setpoint, mm/min or min). Belt speed or dwell time in the sterilising zone (Annex 1, 8.67).
- Pressure differential (limit, Pa). Pressure profile along the tunnel, set by the site and correlated with the heat studies in validation (Annex 1, 8.67).
- Endotoxin log reduction (derived, log10). Minimum 3 log10 in validation, with a suitable Fh value (Annex 1, 8.68).
- Installed filter leakage (limit, % of upstream challenge). Supply filters tested at least twice a year against the site’s test method (Annex 1, 8.67).
SPEQ publishes no universal alarm or acceptance values: they depend on the process, the product and the site’s own qualification.
CONTROLS, ALARMS AND INTERLOCKS
- Control loop: Zone temperature control. Holds each zone at its setpoint.
- Interlock: Belt stop on low temperature. Stops containers passing through a sterilising zone below its limit.
- Alarm: Pressure profile or airflow out of range. Warns that grade A protection at the exit may be lost.
- Procedure: Cycle and run record review. Each run recorded and reviewed in batch release (Annex 1, 8.45, 8.50).
An alarm asks for a response; an interlock stops an action; a safety function protects people and has its own risk basis.
HOW IT FAILS
- Pressure profile reversed. Air from the washer side or the room reaches the sterilising or cooling zone.
- Belt speed too fast or a cold zone. Containers under-processed for endotoxin.
- Filter damage at high temperature. Particles shed onto sterile containers.
- Containers fallen or stacked on the belt. Slow-to-heat positions not represented in validation.
ASSURANCE ACROSS THE LIFECYCLE
EXAMPLES, NOT A MANDATORY LIST- Qualification (Annex 1, 8.70). Heat distribution and penetration, minimum and maximum loads; Air speed, air quality and pressure profile.
- Validation (Annex 1, 8.68, 8.69). Endotoxin challenge with reconciled spiked containers, recovery shown; Fh value at the slowest-to-heat location.
- Routine. Zone temperatures, belt speed and pressures for every run; Filter integrity at least twice a year.
- Periodic. Revalidation of worst-case loads at least annually (Annex 1, 8.39).
WHAT THIS DOES NOT PROVE
- Reaching sterilising temperature does not prove endotoxin was destroyed. Instead: Endotoxin challenge results with a minimum 3 log10 reduction (Annex 1, 8.68).
- Correct zone temperatures do not prove the cooling zone kept containers in grade A air. Instead: Pressure profile, airflow and particle results at the exit.
- One container format validated does not prove another. Instead: Validation with containers representative in material, size and volume (Annex 1, 8.69).
SOURCES
2 CITED- EU GMP Annex 1: Manufacture of Sterile Medicinal Products — European Commission (EudraLex Volume 4), 2022 revision, in operation 25 August 2023. EU / EEA; revised jointly with the PIC/S Committee; in force. Supports: Heat sterilisation records, probes and cooling (8.50–8.53); dry heat principles (8.66); tunnel airflow, filters and parameters (8.67); depyrogenation validation (8.68, 8.69); ovens (8.70).
- EU GMP Annex 15: Qualification and Validation — European Commission (EudraLex Volume 4), 2015. EU / EEA; in force. Supports: Equipment qualification and process validation approach.
HOW THIS PAGE WAS CHECKED
Researched and checked against the sources above by SPEQ (Claude) on 2026-10-21. It has not been reviewed by an independent engineer. It teaches how this kind of equipment works and is assured; it does not say any site, asset or process is qualified, validated or compliant.
- No time–temperature figure is given: the combination depends on the validated process and Fh value.
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