You’ve probably seen them on plastic containers, the little numbers contained in a three-arrowed recycling symbol triangle. These are a code that tell you what sort of plastic you have. They were started in the late 1980s by the plastic industry to help with recycling.

There are seven codes and they’re listed below.

1. Polyethelene or PET – polyester fibers, pop and water bottles and the plastic straps that hold bundles together
2. High-density polyethelene or HDPE – the hard plastic found in bins, equipment and other rigid plastics
3. PVC – water and electrical pipes
4. Low density polyethelene or LDPE – plastic bags, tubing and some bottles
5. Polypropelene – ducting, auto parts, food containers
6. Polystyrene – styrofoam, rigid knick-knacks, video cases
7. None of the above – yes none of the plastics above.