Electrical Safety Warning

Exposed wiring of more than 35V (DC or AC) requires supervision by a qualified faculty or staff member.

Disassembly of equipment which operates on more than 120V mains is particularly dangerous (e.g. 220V appliances); undergraduate student projects involving such work should only be permitted by special exception and under close supervision.

Inspection Items for student equipment with exposed potentials higher than 35V:


  1. Is the wiring well constructed, unlikely to break free in operation, with strain relief as needed? Is the insulation appropriate?

  2. Is the high voltage wiring enclosed in a grounded or insulated case? Will this case always be closed when the equipment is energized?

  3. Are students aware of where dangerous voltages may be exposed and of any capacitors that may retain charge?

  4. Is the equipment properly fused (electrical shorts are the number one cause of laboratory fires)?

  5. Are any sensor wires which leave the higher voltage area appropriately isolated from contact with such voltages?

  6. Could a single component or wiring failure expose a user to a dangerous voltage?

  7. Do any capacitors with dangerous voltages include appropriate bleeder resistors?

  8. Are wiring and electronics appropriately shielded from any high temperature regions?

  9. Are there plans to ensure that it will not be operated unattended, or operated by people who are unaware of the potential hazards? (Unattended operation or operation by novices requires construction and testing to a higher safety standard.)

  10. Are students aware that they should never work alone on equipment where they may be exposed to dangerous voltages (find a lab buddy)?

  11. Can a GFI circuit be used to improve safety?

  12. Is there a possibility of use in wet conditions, where extra precautions and lower voltage limits may be appropriate?