Re. Ladder experience.
SWMBO'D & I did many a brewery tour in our younger days with old open squares.
We were ALWAYS counselled AGAINST sticking our heads over the top and BREATHING in when climbing those ladders.
The CO2 could knock you out, instantly.
I've heard this, and seen stories of brewers knocked out from CO2 fumes (having enjoyed the fruits of their labour through the working day)
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Think this one was towards the end of fermentation and I only had a perfunctory glance over the top. Smells coming off were fantastic though!