5 things you always wanted to know about ‘Dry Ice’
It’s solid carbon dioxide often supplied in pellets, slices or blocks
How ‘cold’ is dry ice?
It is very cold, minus 78°Celsius! You should never handle dry ice without proper thermal gloves to protect your hands against cold burns and frostbite. You also want to protect your eyes by wearing protective eye goggles when handling it. Eyes are very delicate and precious; contact with dry ice at -78° C could cause serious injury to your eyes.
Why is ventilation so important with dry ice?
Dry ice sublimes, meaning it turns from solid into gas. Just a small amount of the solid dry ice produces a very large volume of gas 10kg = 5.4 m³ of gas. The gas produced by dry ice is colourless and odourless. At low concentrations it may cause increased respiration and headache and at high concentrations it can asphyxiate. Normal concentrations of carbon dioxide are 0.035% and concentrations above 0.5% can be dangerous. For this reason, ventilation when packaging and storing dry ice is really important.
How should I safely package my samples in dry ice?
You should never put dry ice inside a sealed container. We are often provided with screw-top plastic containers to transport samples, you should never put it inside these containers as the ice will sublime, creating increased pressure as the gas concentration rises and the container will eventually explode potentially hurting someone. You want to put your sample inside the sealed container then put that sealed container on the dry ice. It is nicely transported in those polystyrene boxes with loose fitting lids. This loose fitting lid allows the gas to escape and keep the pressure in the box low, avoiding any explosions. The package should then be secured and isolated where possible. It is not a good idea to transport dry ice in the passenger component of a car for example.
How can I dispose of dry ice when I no longer need it?
It is best to identify a safe, well ventilated area to allow the dry ice to sublime over time. Proper ventilation will decrease the risk of carbon dioxide in the gas from reaching dangerous levels in the room. You also want to make sure you are not putting anyone at risk so an identified area, where only those aware of the risks when using dry ice have access, would be best.
Sometimes you order dry ice then a patient does not show or is unwell and you don’t collect your sample to ship on the dry ice. You might want to ask your local lab if they would accept any extra dry ice. They often use it to ship samples during the day and as dry ice is very expensive, they will likely be delighted to accept your donation.
3 important things NOT to do when disposing of dry ice
Do not add water to dry ice as this increases sublimation.
Do not place dry ice in a working freezer; it is best kept in an insulated chest designed for this purpose.
Do not dispose of dry ice in a sink or the toilet as it can damage pipes and you won’t make any friends in Estates!
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