In a student at the time we must have this kind of memory, in after-school students are rushing to help the teacher effaceurs and white chalk dust on the covered body, the hair, the clothes on there hands with chalk Gray, laughing while also using these lime mischief with the students, we simply may not have such a sense, these white chalk being unknowingly into our respiratory tract, and the entire respiratory system caused great harm, The long years of standing on the podium to teach teachers are the biggest victims, and with advances in production technology, and now there have been dust teaching chalk, chalk this when in use does not produce dust and are no toxic, heavy use of this chalk can give teachers and students a healthy classroom.

Now teaching chalk dust penetration is not very high, especially in some economically backward, poor teaching conditions in primary schools, due to insufficient economic base, these places are still the most traditional chalk, and many chalk factory chalk provided no guarantee of quality, there are many problems chalk or production of material hardness, if mixed into the body of toxic and harmful things, then the harm caused will be very serious, so the school must buy chalk in time choose a regular chalk manufacturers.