1) Fragments cut disposable lunch boxes, placed in containers filled with water, if you press into the water it is easy to come up, that isn't in calcium carbonate; if youcan't float, sink, by adding calcium carbonate, should not be used;
2) Heated lunch box should be no smell, odor, and should not be used;
3) PP plastic has a certain toughness if feel soft, broken even one tear, should not be used;
4) Many lunch boxes with PP, lid with PS, remember not to be put into the microwave heating cover;
5) Buy brand or QS numbers mark products safer.