How To Judge Whether Students' Desks And Chairs Are Qualified?

1. White powder will appear on the surface of the traced place with a fingernail;

2. Put the stool upside down on the wall or close to the wall (note that the arm is at a 45-degree angle to the wall), the color difference between the part without trace and other places is obvious;

3. Put it in an indoor ventilated place for about 5 days to see the better effect;

4. Stick two pieces of A4 paper in the same position and press them tightly, leaving a gap of 0-5mm in the middle.