# Why does the ISS crew wear a dust mask in BEAM?

This video from NASA shows Jeff Williams entering BEAM for the first time. He's wearing a simple dust mask. Why is that? If there is concern about floating particles, wouldn't there be a concern with leaving the hatch ajar?

• Really good question!! One of the constant concerns on the ISS is inadequate air circulation as a consequence of microgravity as well as long, narrow, tunnel-like architecture, which could lead to local build-up of $CO_2$ or contaminants. So there's a whole network of recirculation ducts and fans to avoid "dead space". You (or I) might ask if, in addition to the hatch being open, if there is forced circulation through the hatch as well. Either way has consequences. – uhoh Jun 8 '16 at 1:31
• Note the goggles as well. This suggests to me it is a particle/dust concern. Perhaps the safety risk of having the hatch to an untested module closed with someone inside just outweighs the risk of dust circulation? – Andrew Jun 8 '16 at 7:37
• I think I'd want a tethered line on me on these first few inspections of the BEAM. Just in case the skin rips and I need out of there really quick. – Howard Miller Jun 10 '16 at 1:00

The planetary society had a nice article on this: http://www.planetary.org/blogs/jason-davis/2016/20160606-first-look-in-beam.html

Williams and Skripochka wore face masks as they entered, which is standard procedure for initial inspections of cargo ships visiting the station.

• Excellent. @uhoh explained this, so combined with this link we have the complete picture. I wonder if they removed masks for the second "visit". – tedder42 Jun 8 '16 at 16:19
• This doesn't really explain why it's standard procedure, though. Presumably it's because of particulates, but I don't think that mask is doing much to protect against a "local build-up of $CO_2$". – Chris Jun 8 '16 at 17:41
• Definitely dust, those filter masks do nothing for CO2. – Organic Marble Jun 8 '16 at 21:37

They also wear the masks when they add a new module to the station. Less so now, with assembly mostly complete.

On Earth, when they are packed, all sorts of stuff settles, no matter how clean-room an approach is taken. During launch lots of disturbances in the Force (gravity forces) occur, and stuff gets shaken around a lot, and they are unsure what will be in their faces when they open it.