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What is dry ice cleaning

Dry ice cleaning is a process in which dry ice is used in a combined system with compressed air to clean surfaces.

Characteristics of dry ice cleaning

It is a non abrasive cleaning method, that will not penetrate the surface of the object that it is shot at, but it will still remove surface contaminates. There is no secondary waste as the dry ice will sublimate into CO2 gas.

What is dry ice

Dry ice is CO2 in a solid state. It is formed when CO2 liquid is release in a controlled environment. The normal temperature of dry ice is about -80 degrees Celsius.

Dry ice have the physical characteristic that is called sublimation. Sublimation is the process in which a solid change state directly from a solid into a gas as shown in this picture.

Thanks to wikipedia for this image!!!

What is the dangers of using dry ice

Well as all know, dry ice is a CO2 mixture. However the safety aspect on exposures are very different as the dry ice is in a solid state of the CO2 mixture. Human exposure limits is measured in Short term exposure limits (STEL). STEL is defined as the maximum parts that a human being maybe exposed to, measured in parts per million (ppm), to be safe. The STEL of CO2 gas is 30000 ppm, and for dry ice 54000 ppm.

What happens during the dry ice cleaning process

During the process, dry ice particles get propelled with high pressure air.The dry ice nozzle is aimed at the surface that needs to be cleaned. The air propelled dry ice pellets hits the surface. Due to the temperature; cold (-80 degrees Celsius) and force (adjustable on the dry ice machine and compressor) at which it hits the surface, contaminants on the surface will crack,the O2 part of the CO2 will cause an explosion, this will rip the contaminants of the surface leaving the surface without any contaminants.

What is the rate of expansion when dry ice sublimates

Dry ice is CO2.
Molar mass CO2 = 44 g/mole
1 lb is approx. 454 g
thus this = 454 g x 1 mol/44 g = 10.3 moles of CO2
At STP, 10.3 moles x 22.4 L/mole = 231 liters.

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