Learn more. What causes compressed air from "Dust Off" cans to freeze, but only when turned upside down? Ask Question. Asked 10 years, 5 months ago. Active 3 years, 4 months ago. Viewed 50k times. Improve this question. Thomas O Thomas O 3, 6 6 gold badges 28 28 silver badges 33 33 bronze badges.
Or fluorocarbon? Or similar. Don't get hung up on my terminology, I'm only an entry-level physics student. Add a comment. Active Oldest Votes. Improve this answer. Colin K Colin K 6, 1 1 gold badge 26 26 silver badges 40 40 bronze badges. The liquid has to have a vapor pressure greater than one atmosphere, ie have a boiling point below ambient. To discourage huffing, a bitter agent is added to make the duster taste bad.
Of course, these types of risks are not as high in an industrial environment, so concern turns to bitterant as a contamination on sensitive surfaces like electronic circuit boards. Retail duster can come in a variety of fill weights the content of the material in a can including 3.
The can size might be the same, so it is important to check the fill weight on the label. Are Nonflammable Aerosols Available? Related Products. Economical, extra-strength general purpose compressed air duster. Economical, regular strength compressed air duster. Ultrajet Ultrajet All-Way. View Details. Reusable compressed air can duster system with a precision surgical-grade chrome trigger valve.
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For example, if you spray a keyboard, you'll see a thin white layer of frost form on the keys briefly. With prolonged use of the canned air, you might notice that the force of the air stream weakens over time, and the can becomes too cold to comfortably hold in your hand. The heat energy from the can has all gone into evaporating the liquid inside; when the can itself becomes cold, not enough heat remains to vaporize more liquid.
To remedy the "out of breath" condition, set the can down and let it warm for a few minutes. This restores the strength of the air bursts. The can carries a warning label telling you to avoid spraying onto your skin; the rapid absorption of heat can easily cause frostbite. The frost that forms on the can and nozzle comes the condensation of water vapor in the surrounding air.
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