I found an unused gas cartridge near where I live about a week or two ago. Today, I found an empty/used one at the same spot again. So my question is, what's inside that cartridge? This kind of cartridge is commonly used to store nitrous oxide or carbon dioxide. Nitrous oxide cartridge is commonly used as a whipping agent for whipped cream, because nitrous oxide is soluble in fat. Carbon dioxide cartridge is commonly used by cyclists who have too much money.

I have a suspicion that this cartridge contains nitrous oxide, because nitrous oxide has euphoriant effects if inhaled. I have a feeling that people who live near me have been committing substance abuse. This is because it is unlikely that the same (group of) cyclist(s) would get tyre puncture at the same spot within a 2 week span and end up using carbon dioxide cartridge in both occasions. Carbon dioxide cartridge is not exactly cheap.

If the cartridge contains carbon dioxide, upon discharge into calcium hydroxide solution, the solution would turn cloudy due to the formation of calcium carbonate. The balanced equation is as follows:
Ca(OH)2 + CO2 = CaCO3 + H2O