Can I use dry ice in a cooler?

Yes, you can. Dry ice keeps things frozen for days, but you absolutely have to vent the cooler and never touch it with bare skin. Dry ice sublimates and expands to about 800 times its volume, so crack the lid or use a cooler with a pressure relief valve to avoid rupture. Also, use insulated gloves or tongs, and don’t let dry ice touch food directly — wrap it in paper or a towel and pack it on top.