What is the primary safety rule regarding the use of dry ice?

Using dry ice, which is solid carbon dioxide, necessitates specific safety measures due to its ability to sublimate and produce carbon dioxide gas. The primary concern with dry ice is the potential for asphyxiation in enclosed spaces. As dry ice sublimates, it can displace oxygen in the air, leading to suffocation hazards if used without adequate ventilation. Therefore, utilizing dry ice in a well-ventilated area ensures that the carbon dioxide gas disperses, mitigating the risk of oxygen depletion and creating a safe environment for those working nearby.

While the other safety measures regarding dry ice—such as avoiding direct skin contact due to its extreme cold or not storing it in airtight containers—are important, they do not address the immediate environmental risk posed by carbon dioxide accumulation in confined spaces. Hence, the choice emphasizing ventilation is the most critical rule for ensuring safety while handling dry ice.