SOP: Gas Supply Qualification for Cell and Gene Therapy and Single-Use Manufacturing

This is a ready-to-use SOP. It covers the gas-supply questions that a conventional compressed-air or process-gas qualification does not fully answer: cryogenic storage vessel pressure relief, CO2 supply into open cell culture, and single-use bioreactor gas overlay and sparge filter integrity at the disposable-assembly level. Replace every <<FILL: ...>> placeholder with your own specifics and route it through your document control, review, and approval. A worked filled specimen follows. Verify each cited standard against the current source before you rely on it.

Document control header

1. Purpose

This procedure covers gas-supply qualification unique to cell and gene therapy and single-use manufacturing, beyond the facility gas system.

2. Scope

Applies to liquid-nitrogen storage systems used for cell therapy intermediates and drug product, CO2 supply to incubators and open culture operations, and single-use bioreactor and bag-assembly gas paths at the sites listed in the header. It does not replace the facility-level ISO 8573 and pharmacopeial-monograph gas qualification covered in <<FILL: facility gas qualification protocol ID>> and Clean Utilities Qualification; it extends that qualification to the points where this material is used.

3. Responsibilities

4. Definitions

• Cryogenic storage vessel: a dewar or bulk tank holding liquid nitrogen in liquid or vapor phase for cell therapy storage.
• Single-use (disposable) assembly: a pre-sterilized, single-campaign bag, tubing, and filter set used in a bioreactor or similar unit operation, replacing a fixed stainless system for that function.
• Gas overlay / sparge: gas introduced above (overlay) or bubbled through (sparge) a culture to control headspace composition or dissolved gas levels.
• Pre-use integrity test: an integrity test performed on a filter immediately before use on the specific unit about to run, as distinct from a design-level integrity rating established by the supplier.

5. Procedure

5.1 Cryogenic storage gas supply and pressure relief

1. Confirm each cryogenic storage vessel has at least <<FILL: number, commonly two>> independent pressure relief devices (for example a relief valve and a separate rupture disc), sized per the vessel specification and the applicable Compressed Gas Association guidance (CGA S-1.2 and S-1.3 cover relief device standards for compressed gas).
2. Verify the relief device set point against specification at installation and at each scheduled reverification (section 5.4).
3. Confirm low-level and low-pressure alarms are wired to a monitored point and tested for function at installation and on the periodic schedule.
4. Confirm the storage unit’s temperature mapping is qualified separately per <<FILL: temperature mapping protocol ID>> (see Temperature Mapping Qualification); this SOP covers the gas-supply and pressure side only.

5.2 CO2 supply to open cell culture operations

1. Confirm the CO2 source meets the applicable USP or Ph. Eur. carbon dioxide monograph for identity and purity; review the certificate of analysis for each lot or bulk delivery.
2. Confirm a point-of-use sterilizing-grade filter (commonly 0.2 micron hydrophobic membrane) is installed on every line that delivers CO2 into or near an open culture vessel, and that the housing allows in-situ integrity testing.
3. Integrity test each point-of-use filter at <<FILL: frequency>> and before first use; record results on the log in section 8.
4. Where CO2 is delivered through an incubator with its own internal HEPA-filtered recirculating air, confirm that filter is part of the incubator’s own qualification and is not substituted for the CO2 line filter.

5.3 Single-use bioreactor gas overlay and sparge filter verification

1. Obtain and review the single-use assembly supplier’s validation package for the gas filter(s) on the overlay and sparge lines, including extractables and leachables data and the filter’s rated integrity criteria, before the assembly type is approved for use.
2. Before inoculation of each run, perform a pre-use integrity test (automated pressure-hold or diffusion test through the bioreactor control skid, or a manual equivalent per the assembly manufacturer’s instructions) on every gas filter in the assembly.
3. Do not proceed to inoculation on a filter that fails its pre-use integrity test; quarantine the assembly and raise a deviation.
4. Record the pre-use integrity test result against the specific assembly lot number, not just the assembly type, so a per-lot trend can be built.

5.4 Ongoing verification and requalification

1. Reverify cryogenic vessel relief device set points and alarm function at <<FILL: frequency, e.g. annually>> and after any vessel, valve, or alarm system change.
2. Trend CO2 point-of-use filter integrity results and vessel pressure/level data; investigate any adverse trend before it becomes an excursion.
3. Any change to the single-use assembly design, supplier, or gas filter rating goes through change control with an impact assessment on the qualified state, per Change Control for Validated Systems.

6. Acceptance criteria

• Every cryogenic storage vessel has the required independent relief devices, each verified to its set point, with functioning low-level/low-pressure alarms.
• Every CO2 point of use into open culture has an integrity-tested sterilizing-grade filter, with records current.
• Every single-use bioreactor gas filter passes its pre-use integrity test before inoculation, recorded against the specific assembly lot.
• All deviations are recorded, assessed, and closed before the affected material or batch is released.

7. References

USP / Ph. Eur. monograph for carbon dioxide. CGA S-1.2 and S-1.3 (pressure relief device standards for compressed gas). Clean Utilities Qualification for the facility-level ISO 8573 and pharmacopeial gas framework this SOP extends. Sterilizing-Grade Filtration Validation for the general filter-integrity testing approach applied here at the single-use assembly level. EU GMP Annex 1 (2022); 21 CFR 211.46, 211.63, 211.67.

Confirm the current version of each reference before issue.

8. Record generated: gas supply verification log

9. Revision history

10. Approvals

Filled specimen

The following shows the verification log completed for an example single-use bioreactor run, so you can see the level of detail expected. The company, system, and numbers are illustrative; replace them with your own.

In this example the bag assembly’s gas filter was tested on the specific lot about to be inoculated, not assumed sound because the facility gas supply upstream was already qualified and the assembly type had passed before. That per-lot, pre-use check is what closes the gap between a qualified facility system and a verified single-use gas path.

Common inspection findings this SOP prevents

• A single-use bioreactor’s gas filters assumed sound because the facility gas supply was qualified, with no pre-use, per-lot integrity test ever performed.
• A liquid-nitrogen storage vessel qualified only on temperature, with its relief devices and alarms never brought into the quality program.
• CO2 delivered into an open culture vessel through a filter that is changed on schedule but never integrity tested.
• Supplier validation data for a single-use assembly accepted without site review, or review that stops at “the supplier said it passed.”

How to adapt this SOP

1. Set your document number, owner, and effective date in the header.
2. Name your real cryogenic storage systems, CO2 points of use, and single-use bioreactor platforms in sections 5.1 to 5.3.
3. Set the reverification and trending frequencies in section 5.4 from a risk assessment, not a default copied from elsewhere.
4. Point the change-control and filtration-validation cross-references at your actual procedures.
5. Confirm every regulation and standard in section 7 against the current published version before issue.