There is no OSHA standard that addresses that. If the machinery poses an unusual hazard for one person than they may be cited under the general duty clause. It is difficult to answwer because your question is rather vague and doesn't explain the situation. Maybe I can give a better answer with more details, sorry. ADDED: I tried to return your message with the additional details but your email wasn't confirmed. If the employees are working alone, do a job hazard analysis and use diligence in reducing the probability of accidents occurring, either through additional safety devices such as interlocks, or additional training. When employees work alone they are more likely to cut corners and when they are on overtime fatigue can contribute to a higher risk of accidents.
