Twenty years ago, Tyvek® drawstring bags were considered an ideal way to wrap pharmaceutical production equipment for steam sterilization. These were being used as the outer bags for big, heavy filling machine parts like stopper bowls, hoppers, and tracks. Back then, most aseptic pharmaceutical plants were still operating with conventional filling lines, before RABs and isolators became the norm.
The main reason companies were switching to the use of drawstring autoclave bags was because industry experts advised against cutting anything in the Grade A space, for fear of generating particles. Also, according to top aseptic consultants, the aseptic presentation of the critical equipment needed to be improved, compared to how things were done in the past, where companies were wrapping parts in cellulose based Bioshield paper and autoclave tape.
Fast forward to today, where isolators and RABs are now commonplace. These large, outer autoclave bags don’t need to be, nor could they be, effectively opened in Grade A. This is done in Grade B for RABS and in Grade C for companies using isolator technologies. The more important concerns today are ensuring that the autoclaved parts are clean from a particulate standpoint, rendered sterile, dry, and free from any residues. However, the drawstring closure design of larger, Tyvek® bags makes it extremely difficult to get the folds and creases of the twisted “gooseneck” closure design completely dry —; and the torturous path closure can be difficult to defend to an outside auditor, or regulatory authority, especially if autoclaved parts are not unloaded and allowed to cool under Grade A LAF before being moved into Grade B/C storage prior to use. While it may not be possible to see it upon removing and inspecting the load, it is likely that there will be condensate present inside the bag, regardless of how long the autoclave drying cycle is extended.
The other concern that has recently come under scrutiny is the chance for residues to visually present themselves on the equipment, post sterilization. This is most commonly observable on brand-new, stainless -steel parts with a mirror finish. The type of Tyvek® (1422A) that was available during that time has always had a water-soluble anti-stat agent applied to it, and there is a good chance that when the steam condenses on a piece of equipment that is wrapped in a drawstring bag design, it will leave a trace residue behind on the equipment after the water droplet is dried by convection. While this residue is not harmful, the fact that it is reported, requires an investigation.
From experience, it has become clear that this phenomenon can be exacerbated by the oversized drawstring bag design. The excessive amount of hydrophobic material traps the steam in its gaseous state and allows it to condense into water droplets. When unwrapping, this residual moisture (anti-stat agent in solution) could be dispersed throughout the bag and transferred onto the equipment parts.
Keystone Cleanroom Products has taken a holistic approach to solving this problem and is offering a solution. We believe the most important step is to “right-size” the bags that are in use; and suggest the consideration of switching from an oversized drawstring closure design to one that can be hermetically sealed, which is, along with dryness verification, a requirement of the new Annex 1 guidelines.
Keystone’s newly introduced PureClean™ 1421B Tyvek® material, from DuPont™, might also be considered as a replacement for the legacy 1422A type. We are honored to partner with DuPont™ to offer the next generation Tyvek® to our pharmaceutical manufacturing customers. The PureClean™ Tyvek® is essentially the same material as the legacy Tyvek®, except it does not have the anti-stat agent.
