After reading your interesting article of managing the ice box I wondered if anyone has tested the use of dry ice? I wonder about it's longevity and safety?
Sue & Larry respond:
Your question about using dry ice in the ice box on a sailboat is an interesting one. We've never come across or heard about a boat using dry ice, nor does the dry ice industry seem to promote its use for recreational boating. That's probably for a number of reasons.
Dry ice does not melt, but rather it sublimates. This means that it changes directly from a solid into a gas bypassing the liquid form. The gas formed during sublimation is carbon dioxide which is heavier than air and displaces the oxygen. The result can lead to a difficulty with breathing, and in higher concentrations unconsciousness or death due to asphyxiation. Dry ice must therefore be used only in well-ventilated areas. This certainly excludes its use in the icebox aboard most sailboats.
On the practical side, even without the pitfalls of displacing oxygen, dry ice is not readily available in many of the places a sailboat is likely to travel. If you did find it, you'd have to use protective gloves in handling to avoid cryogenic burns. Lastly, we're not sure how easy it would be to maintain a cool temperature without freezing certain items in the box. Thanks for your question, and happy sailing.