We use them all the time, and then, when they’re empty or stop working, we often throw them in the trash without a second thought. But is that the right thing to do?
Most spray cans (aerosol cans, to give them their proper name) contain organic solvents and a propellant, the substance that keeps them under pressure and allows them to spray out as a mist. Some use carbon dioxide as a propellant. But the most common propellant: propane and isobutane. Those are extremely flammable (ever try to make a flame thrower with hair spray? Don’t do it – it’s playing with fire. The reason it works isn’t because of the hair spray as much as it is the propellant).
If you throw that can away before it’s completely empty, you create a fire hazard for those who handle it downstream. And you may be polluting the groundwater, if the container ends up in a landfill. The solvents in aerosol cans are often regulated as hazardous waste.
What are your options?
If possible, use up the container completely. And then check that it’s really empty before you toss it and grab the next can. Shake it – can you hear any liquid? Try to spray some out. Will anything come out? Try it upside down, sideways, and then right-side up again. If you get nothing when you depress the nozzle and you hear nothing when you shake the can, it’s safe to throw away. We’d prefer it if you recycle the metal. But it can go in ordinary trash if your waste hauler okays that.
What if you can’t use it up completely? The Minnesota Pollution Control Agency (MPCA) used to allow the containers to be punctured and drained, as long as you used a charcoal filter to capture the vapors. But those filters don’t capture the propellants. As of January 2017, puncturing aerosol cans is not allowed, unless you have a way to collect both the liquid in the can and the propellant used to pressurize it.
The MPCA will allow businesses to handle aerosol cans as universal wastes. Those are hazardous wastes that are so common that special, less restrictive rules have been developed to handle them. Fluorescent lamps are an example of universal waste.
If you handle aerosols as universal waste, you need to:
- Keep them in a closed container, labeled as “Waste aerosols.”
- Store them for no more than a year. Mark the container with the date you first put the aerosol cans into it.
- Ship the waste cans to a site that has agreed to accept them.
- Keep receipts (this depends in part on where you are. We recommend doing so in all cases, as that’s your proof that you’re handling them correctly).
You don’t need to use a hazardous waste manifest for these.
Bottom line: use it up and recycle, if you can.