To answer your doubt: when you're been doused with an acid or a poison, modesty, as Daniel says, is totally out of the question. Since skin absorption is a function, among other things, of contact time, you want and must stop the contact as soon as possible.

I've worked for decades in mixed company and I've never known anyone, male or female, raise the point of lack of curtains on safety showers (I suppose it is not a sign of sloppiness by the builder, because every single one I saw was without, but to avoid any hindrance to stepping under).

As for the opportunity to strip: as a rule yes, it is best to strip because the fabric keeps the chemical in contact with your body and this may well make matters worse: I've known a case in which a guy got some concentrated suplhuric acid on a leg and immediately put it under the shower, trousers and all: the heat of hydration of H2SO4 brought the first water almost to boiling point and he got a bad burn. Moreover, there are many substances which react with water to release even worse stuff, as Daniel discovered the hard way!

For a time I had been lab supervisor in a chemical factory which made a very dangerous and poisonous chemical; we had a special facility where to give first aid to anyone who's been contaminated (never happened on my watch, thank goodness) and one of my duties was to train the personnel on its use.

The first direction was: strip naked and jump under the shower, and, to anyone present (it was forbidden to handle the stuff alone), if the victim is unable to do so, don the safety gloves and help him or her; no one ever objected, because everyone knew what they were working with.

(I know that Americans have a lower modesty threshold than Europeans, but believe me, to save your own skin is more important than to keep it covered!)