Some questions have come up recently about the gowning order-of-operations:
Why are gloves after booties in the gowning protocol now? It seems like it would make sense to limit skin particle contamination from hands in the pre-gowning room area. Also, it makes things more complicated for those carrying in samples with gloves.
Gowning:
A good way to think about the gowning protocol purpose is to start with the goal: Inside the cleanroom, the bunnysuit and the gloves should be clean (as they are in contact with samples/tools). To keep the bunnysuit clean, we store it inside the gowning room (with high air flow) and reduce contamination from body oils/fats/etc by wearing gloves when handling the bunnysuit.
Aside: We gown top --> down (hood --> suit --> boots) since the head generates most particles and because particles primarily fall downwards; we degown down --> top for similar reasons (avoid particles from head landing on bunnysuit shoulders). For the cleanest situations, we would put on a second pair of gloves upon entering the cleanroom. This is a cost/waste/cleanliness tradeoff. We currently don’t do this by default, partly because of lingering glove supply chain issues with nitrile gloves.
Thus, we want to put on the gloves right before entering the gowning room (to keep the gloves as clean as possible). We also don’t want to contaminate the gowning area unnecessarily with dirt from shoes or particles form the head/scalp. Therefore, we need not only gloves, but also hairnet and blue booties. All these are put on in the “dirtier” pre-gowning space. Our “relative” dirtiness scale goes from (very dirty) shoes >> head/scalp >> hands (less dirty). This determines the sequence: booties then hairnet then gloves. If we’d put on gloves first, we might contaminate them when handling our shoes and head.
Aside: During COVID we temporarily switched the glove and booties sequence, out of an abundance of caution related to touch-point concerns (and at the expense of cleanroom cleanliness). Those touch-point concerns are no longer justified and we reverted back to the normal cleanroom protocol.
Sample transfer:
The recommended way to transfer samples is to use a ziplock bag or a sample carrier/box, because you can clean these as you enter and they are sealed off during transfer. Hand-carrying with a glove is convenient and fast, but offers the least protection, and your sample is exposed “to the elements” during transfer, or you risk dropping it when trying to get into the lab.
When entering with samples, you can wipe down a ziplock bag or a sample box with IPA in pre-gown. That way, when you bring the box inside or unbag in the gowning room, you lower the chance of contamination. Even a low-cost plastic box as carrier will help, especially if you can wipe it inside and outside with IPA prior to first use. When exiting with samples, we provide ziplock bags in the gowning room as well as a vacuum sealer (good for shipping/storing samples outside the cleanroom).
We hope this helps clarify MIT.nano's gowning procedures! You can send any questions or concerns to mitnano-feedback@mit.edu.