I wonder if the Korean office workers were already wearing masks? By March, when they picked up these infections, Korea had already been dealing with this for w

I wonder if the Korean office workers were already wearing masks? By March, when they picked up these infections, Korea had already been dealing with this for weeks. And masks were already a thing in Korea. I assume most of them would have been, but maybe not in the office? Or maybe the masks are not that effective in an office environment?