I recently bought a can air compressor. When I used it a white liquid came out (like a fire extinguisher) and it landed on my keyboards. I was afraid so I ran for a napkin. I came back but it was gone. Evaporated quickly. Will this liquid damage my m

"Compressed air" is technically just that -- air (the stuff you breathe) under pressure. It should not contain anything else. A manufacturer may say something is compressed air but if they are including something else it should be on the label and it is up to the consumer to verify the suitability of the contents and the product producer to label items correctly. The product I have says "compressed gas", not "air" which means who knows what the composition is. Plus it says it has a "bitterant" which I presume is something which would make it taste nasty so it discourages people from doing something stupid like putting the straw in their mouths and pressing the button. Anyway, Apple says "compressed air" so if your product has something else in it then it isn't compressed air. What I have in my scuba tank is compressed air.

In the document I linked Apple doesn't really talk about using compressed air. They do warn against using aerosols:

• Don't use aerosol sprays, solvents, or abrasives.
• Don't spray cleaners directly onto the item.

Apple could include a statement warning not all products labeled as "compressed" may be suitable and users should read product labels first. You can send them feedback making this recommendation:

http://www.apple.com/support/feedback/ - Online Support Feedback - "Use this form to send us your suggestions or report any problems you experienced finding support information or using support tools. We'd like to hear about it."

It is probably okay but you have to be careful with compressed air. Not only may it have some chemical in it, it can also come out really cold and you could subject fragile items to thermal shock (sudden cooling). I use it but I don't spray closely, and only for a few seconds. You also want to make sure you aren't just driving dirt deeper into your equipment.

How to clean your Apple products - https://support.apple.com/HT204172

It doesn't even claim to be compressed air so this is really a case where the individual needs to examine a product, evaluating its suitability. I don't know what Apple could do in this case other than tell people make sure you double check what you are buying before using it (that could apply to just about any product anybody buys in any context). I don't know what the white stuff was. The MSDS doesn't mention any additives. http://www.airduster.com/MSDS/AD-001-056-MSDS.pdf I read a few Amazon reviews (which weren't glowing). If it was a liquid and you think it should not have been there then return the product for a refund.

Unless it left some kind of corrosive residue I would think if anything were to happen it would have happened. Given that it evaporated so quickly it probably wasn't water but instead some organic compound.