There are different stir bars for use in lab applications that require a high level of chemical resistance, zero absorption or high heat. You can find stir bars that are Teflon® PTFE coated or Pyrex® glass coated, as well as a variety of others that have specific applications.
Remember that all stir bars are not made alike and to always use stir bars that are compatible with the chemicals you are using!
Bookmark this excellent interactive chemical compatibility chart from Cole Parmer where you can cross reference the chemicals you are using with compatible plastics and metals.
How? Avoid leaving waste containers open — don’t leave them open on a bench top, don’t leave them open in a fume hood!. ALWAYS cap and close a waste container except when you are pouring in waste.