All mechanical equipment should be adequately furnished with guards that prevent access to electrical connections or moving parts; e.g., belts and pulleys of a vacuum pump. Each laboratory worker should inspect equipment before using it to ensure that the guards are in place and functions. Careful design of guards is vital. An ineffective guard can be worse than none at all, because it can give a false sense of security. Emergency shutoff devices may be needed in addition to electrical and mechanical guarding.