You may add the rule of safe experiment in your lab instructions beforehand and emphasise the importance of safety.
Only use safe standard techniques and materials (e.g. simple chromatography experiments).
A food microbiology lab; everybody has food in their kitchen (by default safe). We sent students ready to use dip slides, and told them to incubate in a warm spot in the house. Students are not allowed to open is and should throw it away without opening it. It is important to weigh the risks against the educational benefits. Don’t give experiment that use risky chemicals, but with stuff they already have at home.