Riding out a storm, sealed up tight down below. Watch out for CO2.

[Cpt Pat]

I've twice found myself sealed up tight down below with other crew. All hatches closed, dorades plugged, all vents sealed; to prevent water ingress from a knockdown or roll.

I noticed people having problems with decision making, and generally just becoming progressively dumber. I ascribed it to fatigue. But maybe I was at least partially wrong.

Here's an interesting experiment that shows a cognitive decline at CO2 levels as low as 1,000 parts per million (PPM), and to the point of mental dysfunction with CO2 levels as low as 2,500 PPM. https://ehp.niehs.nih.gov/doi/10.1289/ehp.1104789.

The ambient outdoor level is about 410 PPM (and getting higher as time goes on).

I was taught that crew (sealed in a long metal tube under water...) shouldn't expect symptoms of hypercarbia until the concentration is over 10,000 PPM (1%) -- that's about the threshold where some people first experience a headache. But I don't know if the cognitive effects were ever considered in that number.

Short of installing CO2 scrubbers, I don't know how to solve that problem except to periodically air out the cabin, and risk taking on water. There are CO2 monitors on the market that cost around $100. I'm going to put one in my cabin.