Remember this especially when we buy lots of ice cream during Baskin Robbins 31st day offer. They normally put dry ice in your ice cream pack if you buy a lot.
A friend bought four pack of ice cream and to prevent it from melting, the seller put the dry ice amongst the ice cream. My friend put it at the back seat (not the back of the car) and he started to drive with the windows closed and the air conditioner on (as what we all do).
Soon after that, he had difficulty to breath and it was getting worser by minutes. Luckily, he was in a traffic jam and when he almost fainted, beside him was an ambulance. He dragged himself to the ambulance and got the oxygen treatment. He was getting better on the way to the hospital.
The ambulance officer drove his car to the hospital and he had the same experience. However, before his condition worsen, he opened up the window and he can breathe easily. Only later, when my friend has returned to office and told his colleagues about his story, they pointed to him that the dry ice was the problem. WHY?
Dry ice was made of CO2 and when it "melts", it becomes CO2 gas straight away without leaving any wet mark (that is why it is called dry ice). CO2 is easier to be tied up in our blood and thus, when the dry ice sublimes into CO2 gas, it fills the car room with it along with the air conditioner circulation and caused CO2 poisoning. So, don't put the dry ice inside your car if you are using air conditioner with fully closed windows. You must leave the windows open for such situation.
p/s: Hope this will help to prevent any fatality just from a small negligence like this. Imagine if you have your children inside, they might be the first victim.