Reference

Cleanroom & facilities

Filtration arithmetic, gowning and airlock protocol as the real seal, preservation below −130 °C, and media that decay regardless of the room.

Twelve subjects about the built environment of bioproduction, held together by an inversion: the dominant particle source in a working cleanroom is the person, and the barriers are physics that fail on procedure. A garment is a filter whose seal is made of protocol rather than fabric; an airlock’s pressure argument holds only while one door is shut, and its decontamination argument only if given its dwell time; a HEPA filter is not a sieve, and its quoted 99.97% is the worst case rather than the design point; cleaning and sterilisation are a trade and an integral, both decided at the worst point in the system.

The second idea: storage is a countdown. Below about −130 °C biology stops; every degree above is cumulative damage, which is why an excursion adds up rather than happens. Media, meanwhile, decay on the shelf regardless of the room.

And a caution that repeats: a classified envelope is not a validated process.

Start with cleanroom HVAC and HEPA/ULPA filtration — the airflow arithmetic the other pages argue within.

  • Bio-cosmetic production equipment Why cosmetic manufacturing equipment is really two problems — creating interfacial area faster than it disappears, and defending a water-rich product against microbial growth — and where biotech actives break both.
  • Cell culture media The chemistry of cell culture media: glutamine deamidation, photodegradation of riboflavin and tryptophan, trace-element variability as the classic lot-to-lot failure, and why serum-free formulation is hard.
  • CIP and SIP systems Sinner's circle, wall shear and coverage as the real cleaning variables, riboflavin coverage testing, and SIP as a thermal-lethality argument where air pockets, condensate and cold spots set the cycle.
  • Cleanroom HVAC and HEPA/ULPA filtration Impaction, interception and diffusion, the most penetrating particle size, why filters do not remove vapour, and pressure cascade and air-change rate read as recovery arguments under ISO 14644.
  • Cold chain for cell and gene therapies Vitrification versus freezing, the glass transition that makes −80 °C a hold rather than an archive, Mazur's two-factor injury, DMSO toxicity at the bedside, and why excursions accumulate.
  • Cryogenic equipment in biotech Why liquid-phase storage transmitted infection between vials, what a vapour-phase tank trades away, how boil-off sets static hold time, and why oxygen deficiency is the governing hazard.
  • Gowning and contamination control Why humans shed viable particles continuously, what a cleanroom garment actually does, and why gowning qualification measures technique rather than the garment.
  • Media manufacturing equipment Powder versus liquid media manufacture — milling and dissolution order, why 0.1 µm filtration is specified, adsorption and extractables, and why changing a medium is a comparability exercise.
  • Modular and mobile cleanrooms Why a prefabricated cleanroom can be qualified faster, what a small envelope costs in leakage and pressure stability, why transport forces requalification, and how closed processing lowers the classification needed.
  • Pass-through chambers and airlocks Cascade, bubble and sink airlocks and what each protects, why interlocks are the mechanism rather than an accessory, and the dwell-time requirement behind vaporised hydrogen peroxide and UV.
  • pH electrodes and dissolved-oxygen sensors The glass pH electrode as a potentiometric cell with a drifting reference, the temperature dependence of the Nernst slope, Clark versus optical dissolved-oxygen sensing, and why offset correction against an at-line reading is standard practice.
  • Water grades and purification trains Why autoionization caps resistivity at 18.2 MΩ·cm, what conductivity, TOC and bacterial limits each grade actually measures, and why water decays from the moment it leaves the purifier.