Five examples of unfamiliar hazards are listed below. The conductors in high-voltage equipment do not look different whether they are switched on or off, yet the effect of touching them is dramatically different. Liquid nitrogen, despite being extremely cold, can cause severe burns. It does not mix safely with anything. Evacuated glass vessels can implode violently if broken.
Radiation sources can be dangerous if mishandled.
Keep fingers out of high-voltage equipment. Always wear safety spectacles when pouring or transferring liquid nitrogen and do not mix with any other liquid e.g. by pouring it down a sink. Always wear safety glasses when handling glass vacuum equipment. Read and follow the instructions for radiation sources. If an accident happens, go for help to one of the demonstrators or to one of the laboratory technicians.