Because paint thinner is considered a hazardous material, you need to take it to an appropriate disposal facility to get rid of it. You can find your local hazardous waste disposal facility online. From there, simply deliver it or arrange a drop-off to get it properly disposed of. Alternatively, you can throw it away as regular household waste, as long as you take some precautions first. If you only have a small amount of paint thinner left, you can wait for it to dry up and harden. To do this, leave it with the lid off somewhere with good ventilation and that you don’t go in often. Because of the dangerous fumes that paint thinner gives off, you should avoid doing this anywhere you’ll be for more than a minute or so at a time. When the paint thinner is hard and dry, you can prepare to throw it out. Seal the container if it is in one, and wrap this in newspaper until it is completely covered several layers deep. You can now throw it away with your household waste. However, you’re always going to be better off disposing of it at the appropriate disposal facility.